One of the best explanation of how batteries work on TH-cam is on a whiteboard with sharpie, a job done better without animations. Every sentence was meaningful, a thorough illustration.
Very informative, and extremely well-presented! Applicable knowledge delivered in a manner to be understood and used by novices and professionals alike. Thank you very much for making this available!
Wow, that was amazing! Prof Whitacre is incredible and I love the work he does. The presentation was top notch. Ian, this was the channel I've been looking for :)
Thank you, so much, for posting this! I now understand why my plug-in hybrid car has/needs super capacitors and why it makes that whining noise when the engine starts and why that noise tapers off over time. And, he wasn't even discussing that. But, the information he provided on discharge curves that contrast batteries with super capacitors in regard to total available capacity filled in the "blanks" for me. This is an excellent tutorial.
Fascinating stuff. I’ve put it in my “favourites” for reference. . . It’s interesting to see how far we’ve come in just 5 years, with respect to cell cost. . .
... 49:55 A little about battery care, temperatures, electrolyte decomposition. 50:19 LiFEPO4 charging, maximum charge voltage 4.3V, temperatures, battery stability, safety issues. 53:50 Optimal location of temperature sensor on LIFEPO4 battery cell/pack, sensor fuse, not on plastic case but on the elektrode metal bar! 55:20 Overdischarge, below 0V discharge, 58:00 Outside cell temperature, deep inside temperature, monitoring issues. 1:00 Very low temperatures, much more below 0C, -60C...-50C depends on chemistry!, freezing LiFEpo4 batteries in liquid nitrogen. 1:03:00 Discharge 2C, A123 Systems, battery cells in series, BMS, LiFEPo4 batteries from unknown soures, battery pack management costs. 1:-4:00 Cells in string must have the same capacity to lower maitenece costs! The same state of charge
This was so helpful for my Paper, words can't even describe it. Thanks for uploading :) Did he ever give the talk on supercaps? That would probably be equally as fascinating to watch! Greetings from Germany - Mo
I don't know (although I suspect that he did do so) .. This is the only one of his lectures / talks I have a video of .. However , I have little doubt over his many university years in that field , that talks on supercapacitors came up many times .. I just don't have a video of it myself to share.
Great informative video, one thing iam not sure was covered was How important is it to get these LiFePo4 batteries discharged from full charge to a 1/3 or 1/2 charge state while in storage.
First, this was wonderfully insightful. I'm just an EE working in software but the level was exciting to know I was able to follow along with my old school training. :D Second, what manufacturer did you go with? If Thunder-sky, did you find they were consistent on that last plotting? I'm considering them for a home application.
I personally used A123 as a brand of LiFePO4 .. From I've heard Thunder-sky versions are easier to work with (block instead of pouch , and screw terminals instead of tabs), and they are only a little less in terms of energy and power density compared to the A123 Pouch/Tab cells .. Best of luck.
Very very good presentation !! LFP BATTERY getting more attention as TESLA start using them in model3 may be can you share information in advance in LFP battery ??
Hi Ian, thanks for uploading, great video overview. I was wondering if you have any suggestions on any test books that are specific to lifepo4 cathode and anode design and cylindrical call manufacturing? I have come across a few online but as they are pretty expensive I would love it if you could recommend one.
Ian, Guitartec here again with more questions... As I mentioned before, I run an on-line escooter club, so your answers may be posted there, if that's okay? So far, your explanation on LiFePo care and maintenance has been super helpful. A few more questions have been raised that I thought I'd send your way, if you feel like answering? #1 Do LiFePos need to ventilate? We understand getting a lithium battery wet is a big no-no, but what about allowing it to breathe? These are 18lbs Chinese-made LiFePo batteries in a hard plastic(?) box wrapped partially in factory heat shrink. The US distributor suggests sealing them further in plastic wrap to ensure dryness, however, the only holes into the casing that are visable are where the grommeted charging and main wires exit the casing. These holes may also act as air vents- we aren't sure. So we'd like to know if sealing the holes up with silicone would cause some sort of gas build up? #2 is about LiPos with 18650 cells. If a few cells go bad prematurely, can they be repaired and rebalanced again? I guess the same question goes for LiFePos, unless a drastically more complex answer is needed. Thanks in advance for any insight you can provide.
I don't mind my replies or comments being re-posted. #1> LiFePO4 ventilation During normal operation this flavor of battery chemistry has no need for .. nor any benefit in 'breathing' or 'ventilating' .. It's a sealed (water tight and air tight) system .. and when operating correctly should never 'vent' any gasses or liquids. The design intent for allowing ventilation .. is not during normal use .. but to mitigate the potential hazards in case of catastrophic battery or cell failure. If the battery cell has a catastrophic failure .. it can potentially rupture and release both toxic and flammable gasses .. Under those conditions , venting those released gasses can reduce the potential risk during that cell failure / rupture situation .. but that is the only situation such venting is used for .. soo it would be useful / beneficial in that situation .. but not in any other. The cell itself should be water and air tight .. and in a electrical isolating material .. the only external battery cell location you want to actively avoid getting wet .. is the + and - terminals .. for the same reason you don't want any bare electrical connections getting wet .. ie don't spray your garden hose at the live main electrical panel in your house .. bad idea. The bad for Li to get wet you are referring to .. is the chemical insides of the battery cell .. as long as the cell remains sealed .. this should not ever come up in normal operation .. it is only something to be mindful of in case of catastrophic cell failure when the cell ruptures and an opening is created that could allow water to get inside the cell .. say for example during a catastrophic cell failure , the vehicle catches fire , or even the battery pack itself catches on fire ... normal water should not be used ro put out that fire ... because it's bad to spray water into any live electrical circuit .. just like you would never spray water at a fire on the main electrical panel in your house .. bad idea .. and (in the case of the LiFePO4 Battery) because of the potential for the water to get inside a ruptured cell ... thus fire extinguishers that use a dry or (non-water) foam extinguishing agent and that are rated A, B, C .. should be used to put out such LiFePO4 Battery fires .. not water .. such fire extinguishers are readily and easily available in a variety of sizes .. keep in mind .. in the event of a catastrophic battery cell failure .. The battery can potentially 're-start' a fire , until it has used up all it's internal chemical potential energy .. soo even if a fire is out .. such a catastrophically failed battery should be treat with caution. #2> Reviving 'bad' cell. Depends on how and why it went 'bad'. Some yes .. some no. If the case ruptured .. vented some gasses from the inside , or leaked some liquid electrolyte form the inside .. no .. battery is a hazard and needs to be properly disposed of / recycled. If 'bad' as in a given cell is out of balance .. or no longer well matched with the other cells of the pack it is in .. than 'yes' ... that cell can be re-balanced with the other cells of it's pack .. and/or that cell can be re-matched with other cells in a pack re-selection / re-build. etc ... etc ... it depends on the specific details of what kind of 'bad' one is referring to.
Ian, thanks! This is great stuff. Let me post this and see if anyone has any response questions. May take a few weeks. I'll get back to you. Guitartec (Dean)
Great video! Hope to see more from you. We want to replace a stand by battery system 100KW currently built with VRLAs. We'll connect 3 battery trays of 11 or 12 TSWB-LYP200AHA cells in series to make a battery set of 108 V. Each battery tray of 36V has its own BMS. Each battery set has a diode in series and its charged by its own battery charger. In normal conditions the battery charger 25KW will feed the loads on the DC108V bus and when power is OFF we switch to the battery power. Has anyone tried this? Will it work if we have 4 of these battery sets in parallel?
great video on LiFePO4 cells. Thanks. Is temperature increase happen only during discharge? Or will it happen on charge. How to improve the temperature increase during charge. I see mobile phones heat up during charge also
Temperature increase happens on both charge and discharge .. however, not exactly the same .. Mobile phone batteries are chemically very different than the LiFePO4 being described here , there are some similarities but there are numerous differences .. Improve as in 'reduce' the amount of heat increase during charging .. AC charging heats less than DC charging .. or charge slower .. or increase / improve the heat dissipation system .. or add storage in the form of some thermal mass, the most weight efficient of such are phase change compounds.
Can any one recommend a good book about this topic: LiFePO4 please? I really liked this video. It gave me a good overview of that element that form time to time I implement in my electrical designs but I don't comprehend much. Thanks!
Sorry , I don't know off hand of a 'book' , specifically about LiFePO4 ... although there could be a market .. if someone wanted to compile such a text .. There are lots and lots of technical papers on various parts , aspects , and different applications , and treatment of the chemistry.
I'm am at the point of deciding between batteries for my EV (electric motorcycle) . On the top of the scale is the LCO, on the other end is LTO which is the least energy dense but safest. Lifep04 being in the middle of the 2 chemistries in terms of energy density and safety. Would you you say lifep04 is still a good choice for an EV?
To directly answer your question .. I would say .. Yes , in some EV applications a given LiFePO4 battery can still be a good choice .. I would even go so far as to say .. Yes , in some EV applications a given LiFePO4 battery could even be the best possible choice .. but not all LiFePO4 are the same .. and not all applications are the same. .. That being said .. a few other aspects worth noting. LTO and LiFePO4 are not mutually exclusive things .. one refers to the anode the other to the cathode .. it is entirely possible for the same battery to be both LTO and LiFePO4 at the same time. .. That being said .. You would have to define what your priorities are for the EV you you designing / building .. what those priorities are is up to you .. if by 'top of scale' you are referring to energy density .. LCO is not top of that energy density scale .. There are other rechargeable battery options that have higher energy densities , the highest I've ever seen in use is ~500 wh/kg .. but .. as you alluded to .. there is no one battery that is best at everything .. it is always a question of trade offs .. +1 here -1 there .. thus a question of your application priorities .. in some EV applications I could see LCO , LTO , and LiFePO4 all 3 of them being a bad choice .. the devil is in the details of the application. .. My advise .. Just sit down with what your application needs the batteries to do .. power density (charge and discharge) , energy density , operating conditions (temperature, mechanical stresses , etc) , Expected service life cycles/years , budget , limitations of other components you've already selected 9for one reason or another , etc .. once you have all that .. then walk through each specific battery option and see how each one fits your various priorities .. run through the numbers and see how each option would reasonably be expected to perform in you application.
Could one charge each 3.4V cell and cycle it individually and then when recharged set it aside and do this for each cell for the pack. Then hook them all up in series when they have the same state of charge and use them... or maybe hook them all in parallel and cycle the set ... and these would "balance" the cycles or valus?
I would recommend keeping in mind 3 things : #1> balancing is not the same as matching. matching is putting together cells as close to identical twins as possible. balancing is putting together cells as close to the same instantaneous SoC/SoE as possible. #2> There is more than one type of balancing. A top balanced pack might be very out of balance at the bottom. A bottom balanced pack might be very out of balance at the top. A middle balanced pack might be a little out on both top and bottom. etc... #3> Cell Drift Without some type of external system to make adjustments over time .. cells in series usually naturally tend to drift apart (become unbalanced) over time / use / and changes in temperature .. the closer the 'matching' the pack cells are the slower it will happen .. but .. no matter how well 'matched' initially .. no matter how well 'balanced' initially .. eventually over time they will eventually drift apart and become unbalanced , and less matched .. a well matched and well balanced pack (with reasonable type of use) should take several years to drift any significant amount.
Electron from the cathode side during charging is not from lithium. The electron is from the Fe(+2) as it changes to Fe(+3). That's the reason why one uses transition metals for cathode.
Perspective and Context are important: Your comment = describing mainly outside the battery The difference between electron flow and current flow. Because electrons are negative sign (not because of transition metals) .. electrons flow opposite the direction of the current flow .. soo a +flow of current into the battery .. or into the capacitor .. or into the fuse .. or into the light bulb .. or into a wire .. a +flow of current into anything .. that means an opposite direction flow of electrons out of it .. that is just a product of the convention that we give electrons a negative sign in the same conditions we give current flow a positive .. electrons flow in the opposite direction as current .. that's just convention. different perspective and context than This video is mainly describing inside a LiFePO4 battery cell: From a inside the battery point of view / context .. anode electrolyte cathode .. of a lithium based battery .. it very much is the lithium ion that is the charge carrier that flows into and out of either the anode or the cathode through the electrolyte , during charging or discharging .. electrons themselves are NOT the charge carriers inside the cell that move through the electrolyte and into or out of either side anode or cathode during charge or discharge. The true whole picture includes both : Inside the cell perspective / context where lithium ions are the charge carriers moving into or out of each side (anode/cathode) through the electrolyte between them .. and .. the outside the cell perspective / context where electrons are the charge carriers that move into or out of each side (anode/cathode) through the wires we connect to those terminals.
@Ian George Thank you for your answer. But my comment was about your explanation at 8:12. You explain that the electron flow out from the cathode during charging is by stripping off an electron from lithium atom, not from the Fe(+2). As far as I know, the lithium atom in the cathode active material is cationic, not neutral. The phosphate anion stabilizes both of the lithium ion and Iron (+2). If the lithium acts as neutral in the cathode active material, then the battery can't provide 3.2V. That's the reason why we should use transition metal for cathode active material which can provide electrons during charging.
@@techtripkorea You are welcome. I (Ian) do not appear in this video at all at any point .. as I wrote in the video description ... Speaker is Professor Jay Whitacre (that is not me/Ian). Your description of the video is not accurate .. re-watch it if you like .. What Professor Jay Whitacre says at the 8:12 you reference is and I quote .. "I am stripping electrons from my LiFePO4" .. at that point you reference in the video , he is not specifying what part of that LiFePO4 compound gives the electron that exits the cell out that terminal (flowing out opposite direction to the flow of charge current). It might help to think of it like dominoes the Lithium doesn't have to be the 1st initial source of the electron that leaves the cell out of the cathode during charging , but ultimately the lithium is the last one left in the chain to give up an electron at the cathode ... the last thing that lithium does, when it becomes and + charged Lithium Ion and then that Lithium Ion leaves the cathode. It is only as a + charged Lithium ion that it (the Lithium) then travels (diffuses) through the electrolyte , to get to the other terminal (anode) .. while charging strips electrons flowing out of the cathode .. at the same time charging is adding electrons to the anode .. those additional -charge electrons building up on the anode (during charging) attract the +Li ion that left the cathode (when it gave up it's electron to the remaining components making up the remaining cathode compound).
Ian, As I'm writing this, I just realized that LiFePos could come in 18650 cells- insert pic of me with face in hand. I was just sent a pic of an eScooter member's 2015 48V LiFePo battery that has the shrink wrap removed. This is the battery from my last post that has some damaged cells he wants to repair and rebalance. The pic shows 104 pink 18650 cells (13 rows x 8 cells in series). The label cleary says it's a LiFePo battery, but (until a second ago) I thought all 18650 cells were LiPos. The reason is, every LiFePo I've ever seen torn down consisted of alternating large plates with separators, not individual 18650 cells. I guess there's more than one way to build a LiFePo. The question is, is one style better than another regarding high voltage scooter batteries? The spec label on his battery reads; Max Charging Voltage= 54.6V, Max Charging Current= 10A, Continue Discharging Current= 25A, Peak Discharging Current= 50A. If for some reason you suspect this isn't a LiFePo, which is what I did, please let me know. Thanks, Dean
I would say better for specific applications / conditions .. yes ... but one way , better for all possible different applications / conditions .. no. Look at the pros and cons of each method .. look at the conditions it will be exposed to in the given application. For example Plates & separators can add additional pack rigidity , and additional pack isolation in case of catastrophic cell failure , it can help with the modularity of pack design , etc .. but not all applications equally care about such things .. the plates and separators add additional volume/space , weight , cost to the pack .. in some applications the pros of plates and separators outweigh the cons .. in other applications the cons out weigh the pros and they aren't used. There is also variation in the battery design even in the same chemistry .. make the conductive anode/cathode thicker for reduced resistance , and better high current abilities .. but doing so gives up some of the space and weight for capacity .. etc.etc. If you verified that on charge it goes into the exponential terminal voltage shape near ~54v .. not that it entered that long before / lower voltage .. If that Exponential terminal voltage under charge shape shows up at ~50v .. or down at ~45v .. that's the point to note , without continuing to drive and push it to ever exponentially higher voltages .. not what the label says .. what does the battery do under charge ? If you've opened it an verified the connections are 8s that would make the ~54.6v very odd ... 54.6 / 8 = ~6.825v per cell .. that's not right ... if you verified 13s connections .. 54.6/13 = ~4.2v per cell .. Depending on the charge rate .. you should see the terminal voltage on LiFePO4 start going exponential around 3.5v-3.6v per cell .. the higher the charge rate the higher the terminal voltage point at which you reach that start of exponential voltage shape .. but 13s connections of LiFePO4 cells would definitely go exponential long before 54.6v .. 54.6v would be conventional for LiFePO4 used on a 15s pack. Best way to know is to verify some things .. verify if it is 13s or 15s .. what the charge voltage curve , under some known charge rate .. when does it start to go into that exponential voltage shape ... etc .. than, completely separate from the label , you could verify and be fairly certain about the what the battery is .. whatever that is.
Thanks Ian, I have to admit, I understood your first 3 or 4 paragraphs, and I totally appreciate it, but the diagnostic stuff is a bit over my head. Even so, I'll pass on the info. Maybe the owner of this troubled battery will understand it more than I. I'll let it sink in, too. Thanks as always for sharing your knowledge. Dean
Being pink 18650 makes me think(99.9%) they are Samsung Li-ion...Being 13s8p makes me think this is 15ah li-ion battery...Also most all Li-ion are 13 series...Do not use lifepo4 charger with li-ion or vise versa...13s x 4.2v(li-ion)=54.6v or a 48 volt bank! test 1 row of parallel to see voltage when charged up...should be 4 or 4.1 Lifepo4 dont go above 3.7 volts!!! 13s x 3.6v(LiFePo4)=46.8v ,,,,,,Definitely your lifepo4 label is wrong I have several LiFePo4 batteries...They are all 22650, and they are all 16 series..10 ah,20ah and 40ah...My lifepo4 chargers charge at 60v/6a Because 16s x3.6v=57.8 volts...a tad heavier, but charge cycles and steady discharge make up for weight...Take care...
Hello, I have been using 24DC 50Ah batteries for almost two years but I’m concerning about actual real maximum battery capacity. These batteries are working continuously in AGVs, 24h/day, 360days/year... Which is the best way to measure the real maximum capacity? I was thinking about first full charging and then measure discharge current and time. ... Is there any kind of standard DIY design for battery discharging? Regards, Edu
yes .. the best way to know what they really are .. is to test them. Yes, at the very least full charge for the full discharge test. I will also say only the rates you will really use them at are the most 'real'. I also would recommend testing for worst case / hardest .. that way you know that is the minimum they have , and under gentler conditions they will do better. For example : If you know you'll drawl a discharge on them at say ~200Amps .. the most 'real' test is one that reproduces that ~200Amp discharge rate .. if you know you'll only go down to __Voltage or up to __ voltage in application .. than don't go bellow or above that in your test either. Label: Just because they were sold as '50Ah' doesn't mean they actually were 50Ah to start with on day one .. they might have been 49 or 51 .. without test data to go back to .. you just don't know is all. The best comparison is when you compare the results when they are tested the same way .. comparing 50a test to 200a test is a bit of an apples to oranges. ------ Most DIY battery discharge testing often uses things like a known resistance heating element as the discharge load .. take regular rate readings with meter of Amp rate and voltage. But a better test is one that holds that same known rate for the entire test .. soo if you know you're real world load will be say 500Watts , than discharge at a steady constant ~500Watta .. the resistance type will vary the rate as the conditions change .. so, although it can work and is cheaper and easier for DIY .. it is not as ideal / quality of data compared to a more complicated and expensive design that more precisely regulates to the same rate for the entire test.
From mechanical engineering background and worked on IC ENGINE for 15 years I recently developed lot of interest in EV and battery would u please share some vedio for beginners as well
This is the beginner "101" video for LiFePO4 .. Among the other videos I've done 2 that would be good for battery beginners .. One on NiMH nomenclature. th-cam.com/video/zxAtrnfHCtE/w-d-xo.html Also one on the variables that effect battery life cycles / years. th-cam.com/video/DoyrKXvXSBM/w-d-xo.html
I don't see evidence to support your claim .. Where did he make that promise for a 101 on supercapacitors ? .. That claim was not made in this video , as far as I can see. At 9s in he said he "can talk about super capacitors at the same time" .. he did just that , what he said he would do .. several times throughout the discussion on LiFePO4 he did talk about some of the super capacitor aspects at the same time while he was discussing this topic on LiFePO4 .. also .. keep in mind this was a class that went over an entire academic semester .. this is just a short 1hr15m clip from that much longer period of academic time .. and .. at 39.00 he points out the 'come back another time to talk about those' to discuss super capacitors in more detail .. because this was only a short piece of an entire academic year long scholastic activity.
12Watt Solar Street Light on 72Wp Solar PV panel would be powered by 30AH, 12.8V LiFePO4 battery. What other things to be taken into consideration or verified before concluding on requirement?
#1> You need to know the reasonable yield rate from that 72W solar panel .. a solar site survey of conditions / orientation .. that will give you reasonable expected output .. this output will vary as the conditions / orientation varies (such as time of day , time of year , etc) .. this will tell you about how fast the battery is refilled. #2> You need to know the daily use rate (avg , min, max) of the 12w solar light .. 1hour , 24 hours , etc .. this will give you a reasonable estimate of how much you are consuming per day .. this will tell you how fast the battery is emptied. #3> You'll need a BMS of some type to make sure the LiFePO4 cells stay balanced .. you can be a human BMS if you want to do it manually yourself .. or buy a device to automate it for you. #4> You'll need a solar charge controller .. MPPT will yield more wh than PWM .. that fits electrically with both .. the panel output , and the battery design. #5> You'll need a low voltage cut off .. that fits electrically with both .. the output light load , and the battery design. #6> You'll need a properly sized fuse. #7> You'll need a proper container for all of this .. that fits the application conditions .. size, temperature , water , etc.
Sorry, I don't know of one of equal quality as this video from JayW .. The one's I've seen specifically on Super Capacitors are usually far more basic / rudimentary.
Everything eventually degrades. The rate of degradation for LiFePO4 (and most batteries) will vary with the details of it's conditions and usage. If not used, that removes many of the variable usage condition variables. You would be left with SoC level, temperature , and quality of the stored cell itself.. Specifically for LiFePO4 , worst case conditions like storing at top SoC, in high temperatures 40+ Celsius, from low quality cells.. you might see degradation rates as high as around ~10% or so per year .. best case conditions low SoC (not zero) , low temperatures , high quality cells .. than you might see degradation rates less than 1% per year .. as for 'what happens' .. the short version, is that you loose usable energy storage and usable power rates (for charge and discharge) .. a cell initially giving ~60wh would then give less .. ~54wh if as high as 10% .. or about ~59.4wh is as low as 1% .. The cell that initially gave you 3,000w , might now only give you .. ~2,700w @ 10% .. or ~2,970w @ 1% .. So far in my own HEV usage, I'm seeing between 1% to 2% loss per year so far , but that isn't just being stored on a shelf, it is being used almost everyday, year round.
Great lecture, very interesting. I'm interested in the cold temperature characteristics of my Fusion LifePo4 12v 40amp/hr battery pack. It's says they have an operating range of about -20'C to 60'C, which this lecture supports. My concern is that I have read other information saying that it is not ideal to charge these batteries in temperatures below 0'C as this can lead to a coating build up? It gets to -8'C here so I am concerned that after my 4x4 has started its going to try to charge my LifePo4 Aux battery whilst still below 0'C possibly causing damage?
It isn't a black/white thing .. where there is a clear line of A is good and a tiny distance away B is bad .. it's more like a shades of grey thing where A is better than B but B is better than C .. etc .. along a progression from 'good' to 'bad'. As one moves further and further away from good and more and more toward bad .. shorter and shorter useful/operation life (cycles/years) .. 10 years instead of 20yrs .. or 5 yrs instead of 10yrs .. or 1yr instead of 5 yrs .. etc .. only in extreme cases of cell defect or abuse would it just fail , instead of age/degrade quicker. That a cell operates at some temperature does not also mean that it is at 100% of it's ideal temperature operation performance. There is variation even in the general 'LiFePO4' family .. they can be tweaked +this -that etc .. I don't have exact details on the specific battery you have .. That having been said, I can give you some basic principles that apply in general .. and I'll give you an example of how that applies to a specific flavor of LiFePO4 I am familiar with .. If desired you can test your specific battery to quantify exactly where it's specific tweak/flavor stands. In general the battery performs better but ages / degrades faster in hotter conditions .. and the reverse also .. generally the battery will perform worse but age / degrade slower in colder conditions .. the harder you push a cell the faster is ages/degrades .. harder as in .. How wide the SoC/DoD use window .. or how higher power rates (charge or discharge) are used .. or temperature extremes (hot or cold) .. etc .. etc. When the application usage doesn't change to reflect the conditions , the result is to 'effectively' be pushing the cell harder. To give an example of this for a specific battery that I know and have extensively tested .. the A123 version of the LiFePO4 20Ah Pouch cell .. short pulses (as described in the video) can be significantly higher, but the bellow I describe is for the more conservative / safer / continuous use rate. At a temperature of 25Celcius ~60Amp Charge ~200Amp Discharge .. is about as hard on the same cell as ~40Amps Charge ~180Amp Discharge at 15Celcius .. is about as hard on the same cell as ~20Amps Charge ~160Amp Discharge at 10Celcius .. is about as hard on the same cell as ~10Amps Charge ~90Amp Discharge at 0Celcius .. is about as hard on the same cell as ~6Amp Charge ~60Amp Discharge at -10Celcius .. is about as hard on the same cell as ~2Amp Charge ~40Amp Discharge -20Celcius .. This specific flavor (I'm referencing here) of LiFePO4 should not be charged when it bellow -20Celcius temperatures but still roughly equally hard on it to discharge at ~15Amps down to -30Celcius , and should not be discharged below that -30Celcius .. but the cell (if not used) can be slowly taken down to under -100Celcius and then slowly warmed back up and still be fine. Now if I were to take that cell and try to force it to take a 60Amp charge rate at colder than 25Celcius temperatures .. than that would mean I am pushing that cell much harder at those colder temperatures .. even though it is still the same 60Amp charge rate. There can be tweaks and adjustments OEMs can make that will make a specific LiFePO4 cell be a little better or worse than those specific numbers for that specific cell that I described .. but the description explains the concept.
I saw that he referred to discharge under freezing conditions with no problem, however he didnt mention charging under freezing conditions and I've read from other sources that charging in sub-freezing conditions quickly destroys a battery. Can you confirm/deny this?
Maybe I should make a video in more detail .. as this is a common question that comes up on a regular basis. The short version is = It isn't a black/white thing .. it's a perfomance curve , with multiple variables interacting and contributing. Aka: It isn't 100% then 1 degree of temperature different it goes to 0% .. it's a performance curve .. to push a cell equally hard (as far as wear and tear on the cell) .. you would have to actually slow down doing less watts of power (charge or discharge) as it gets colder and colder .. the specific vary of course from battery to battery (even among the flavors of the same type like LiFePO4) .. but if someone properly takes into account that performance curve , you can continue charging well bellow freezing temperatures like zero Celsius .. and (depending on the details) it might not be any harder (as far as degradation) on the cell as higher power rates at higher temperatures are. Also .. this curve starts considerably before freezing 0C temps : For example: Person A ... charges a cell at 10C temps the same as they do at 30C temps .. and never charges bellow 0C temps. Person B .. Charges his cells all the way down to -20C temps .. but they change the rate / method of charging , following the cells performance curve as the temperature changes .. starting with equally hard as person A at 30C temps. In that over simplification .. Person A is actually putting wear and tear on this cells faster than Person B .. although Person B's method is a little more complicated. Some people don't want to think of the slightly more complex (although more accurate) 'curve' .. and instead they try and make it overly and misleadingly simple by just saying the black and white (don't charge bellow freezing temps). Also .. it isn't just the temperature alone .. DoD also matters .. C-Rate matters .. Mechanical Stresses matter .. method of charging ... etc .. etc.
My personal preference .. when it can no longer be reused in another application , and finally must be recycled .. generally speaking .. I would discharge each cell as low as I can .. cell level might not be reasonably possible for some battery packs of multiple cells , in which case just discharge as low as I can be done safely .. if if it is a pouch style cell I'd cut off the tabs .. then I'd cover the remaining +/- terminal area with something non-conductive like a piece of electrical tape .. bring the whole thing to an Li battery recycler .. or ship to one if none are in your area .. some recyclers also have their own specific instructions.
HELP... My escooter uses a Chinese-made 48v 20ah 60 amp LiFePo4. I'm confused at the charging directions because the escooter manufacturer directions say to always charge it immediately after a ride. Alternately, the charger's instructions say there's no need to keep it fully charged, but when you do charge it all the way up, leave the charger on for an extra 1/2 hour after it stops charging to balance the cells.. but that makes no sense to me. Besides, if I do that, the escooter will totally die electrically until I disconnect the battery from the controller, then it works fine after I reconnect it. That seems like a controller issue. Lastly, I saw a LiFePo4 video that stated the longer a LiFePo sits at full charge or at a depleted charge, the less life you'll get out of it. Any charging advice would be appreciated, because I've been given too much Chinese information. Nothing makes sense (and a replacement battery is $750.!).
Its a matter of choice ... there isn't one thing that has all pros and no cons .. you have to learn the pros and cons .. and pick what satisfies your own specific criteria / desires / etc: Item #1> Holding a LiFePO4 battery at a higher SoC or SoE or rest terminal voltage .. holding it up there for more hours .. all else being equal .. will increase the rate at which the battery degrades .. it won't be instant .. it wont' be in a week .. or a month .. but if all else is equal .. the battery that stays at a higher SoC, SoE , or Rested Terminal Voltage longer will age / deteriorate faster ... over years of time. Item#2> An unbalanced battery pack risks putting additional stress .. ie degrading faster .. all else being equal .. the individual cells that reach the top sooner than the other cells in that battery pack ... and also risk additional stress .. degrade faster .. for the cells that reach the bottom sooner than the others in the battery pack .. the faster one hits the top or the bottom the harder the stress .. the larger the imbalance the greater the stress. Item#3> The narrower the SoC/SoE operating window toward the middle the longer the cycle life .. all else being equal .. soo a cell that is kept 90-10 instead of 80-20 will experience slightly faster degradation from the wider SoC/SoE usage window. Item#4> A Warm cell .. all else being equal ... performs better .. it can deliver more power .. has lower resistance .. has more usable capacity .. etc ... but it also degrades faster than a colder cell ... soo one has to pick a compromise point .. where it is warm enough to get satisfactory performance .. but still cool enough to not unsatisfactorily increase the degradation rate. Item#5> The faster / Harder you push a battery .. all else being equal .. the faster it's degradation .. soo .. you again look to find a compromise ... where you get the amount of performance form it to satisfy you ... but don't push it soo hard that is unsatisfactorily accelerates the degradation. etc... Now this last part is the hardest ... weed through compromises of all the various pieces. For example .. a charger that does it's top balancing .. at the top ... wants to do that balancing in order to reduce the effects of a possible imbalance ... but in so doing it automatically gets into that top zone and the cons of doing that ... you probably don't need the balance corrected every single time you charge it .. soo you could choose to shy a bit away from the topping losses .. and a bit more toward the balance losses .. doing less balancing .. but still doing some occasionally ... by not charging all the way to the top .. you are also choosing to voluntarily give up some of your usable range .. if you can do that on both top and bottom , it will also help prolong the usable service life of the battery .. but it will mean you are voluntarily lowering your usable range. Soo you see there are pros and cons ... but .. if you know how they effect your battery .. and what you personally want /need from your battery ... than you can make the choices that are the best fit for your particular usage ... someone else might not have the same wants/needs as you do .. so they might make different choices for different pros and cons. There really is not .. one size fit all.
Well Ian, you've given me some great info here for Summer usage and I thank you for it. So, when I store the battery for the Winter months, I'm thinking I'd balance-charge the battery to 100% and then run it down to about 75% SoC. I'd give it a short charge each month to keep it around 75-80%, unless that's unnecessary??? Also, Do you mind if I post your response(s) on my Escooter Club site on Google Groups?
You're welcome .. happy to help. I don't mind you copying my posts to other threads or such .. Happy to help. The reason to keep it up as high as that 75-80% SoC/SoE .. would be because you want it ready at a moments notice to be used .. If instead you know it is going into winter storage .. and you are not likely to use it .. or you will be able to limit yourself to charge it up just before you want to use it .. than it would be better (in the long run , all else being equal) .. if you stored it at a lower SoC/SoE .. down around 40-50% is better than 75-80. The only need for occasional short storage charges .. would only be needed to counter the amount lost to Self Discharge and any load taken from the batteries by your BMS. Depending on SoC/SoE and on temperature .. it is reasonable to expect a good quality / good condition LiFePO4 cell to have only as low as 1% to at most 4% Self discharge per year .. higher at higher SoC/SoE , and higher at higher Temperatures .. but still it's very very slow on it's own .. some of the BMS people use , drawl more than this and can drain the battery faster than any low Self Discharge it might have on it's own .. LiFePO4 cells that are self discharging faster than about ~5% per year .. I would begin to keep a closer eye on them .. that's far faster than it should be .. might still be usable / manageable for a long time .. but it would still be an indication that something is less than 100% about the cell if it's self discharge rate is that fast. Remember a BMS that drawls even as little as ~1mA .. running 24/7 .. will all by itself ... even at that ~1mA will consume about ~8.7Ah per year .. you will either want a physical disconnect for the BMS to prevent it from draining the cells during storage .. or you'll need to do those short storage charges often enough to counter and replace what the BMS took/used.
Actually it sounds like you have a cell(or 2) with a loose weld...once you hit a bump, your bms cuts out because I parallel set jumps too low...once you reconnect you are good till next bump...it could be loose wire somewhere in between, or in BMS or controller...Check all connections before battery breakdown.I've done a Battery teardown time or 2...R U positive they are LiFePo4???? Are they stock from factory??? NEVER charge battery below 5 celcius! Store a battery for winter at 80% capacity! Full charge is fine, but not all winter!Also dont leave depleted all winter!!!
Ian, i'm the guy that you helped with the escooter Lifepos last year, not sure if you remember? Anyway, I have a idea for people who ride ebikes and escooters with typical LiPo batteries who suffer, like I do, from range anxiety. Is there a way to make a super small, no cord, 52v super capacitor battery booster that one could just remove the battery from the ebike or scooter and plug this booster directly into the XLR charge port (not USB)? This would be to just give the rider a few extra bars on their meter to help get them home. Just wondering if you think this is doable. PLMK if possible.
I have no doubt that would be 'doable' .. however .. That isn't the direction I would personally advise/suggest to someone. 1st I would suggest having a battery range installed that properly fits the application. 2nd Present super capacitors hold much less energy per unit weight than present Li battery options. Even if someone wanted to carry the dead weight around that most of the time they never use .. they would have more joules/calories/wh/etc of usable boost range distance by doing so via a Li Battery (not a super capacitor) .. or they could carry the same extra miles as the super capacitor but it would weigh less. 3rd If someone wanted a hidden/emergency reserve .. it would be smaller space .. lighter weight .. etc .. to just do that in control software , while using the larger (better fit to application) single battery (like 1st above). -- That's just my 3 bits (personal preference).
@@ianpgeorge Well, I guess I should say that this "booster device", in order to be marketable, would have to fit certain criteria and in some aspects may possibly be more form over function in order to be sellable. Having it built into the control software would be nice, but since it's for any ebike or escooter, that would be tough. It would be sold as emergency power to either get you home from a miscalculation of range or give piece of mind to those who often push their battery range or have older batteries with declining range. Again... It's insurance for people with range anxiety. It MUST be super small and light weight, no a/c or charging cords unless self contained, simple to use. Maybe it will have a dynamo hand crank that charges some super caps. Maybe pedaling charges it??? Idunno. What do you think. PS. I have a micro hand crank dynamo I ordered from China. It's sort of junkie and would take a lot of cranking just to partially charge even a phone, but if it were made well, could it charge caps enough to give you a few miles?
Could such a device me made ? yes , absolutely no doubt at all. What do I personally think about it ? There are smaller, lighter, cheaper, more efficient, etc.. ways to achieve the same effect.
There isn't just one (precise) way .. there are numerous ways .. each have their pros and cons .. but the cause is just the choices you're making in your design (as described thus far). You might have any number of perfectly valid reasons (whatever they are) for why you've made the choices you've made .. but whatever your reasons are .. whatever the other (non-functional) benefits they offer .. marketing / press / whatever .. they still have consequences , such as increases to cost , size , and weight. ---- Hit #1> Super-Capacitors They have their pros and cons .. the application you've described doesn't benefit significantly from any of their benefits .. (fast charge , fast discharge , high cycle life, etc) .. at the same time the proposed application is harmed significantly by their cons .. (more expensive , more volume for the same energy , more weight for the same energy, etc). Just by you wanting to specifically use super-capacitors instead of any of the various other options .. you are automatically more expensive, bigger, and heavier than any of those other options that have would have less volume for the same energy , or less weight for the same energy , or less cost for the same energy .. if you don't want this increase in cost , size , and weight .. than drop the intent to use super-capacitors .. or just accept the consequences (cons) of the choice to use super-capacitors. --- Hit #2> 2nd battery hardware You dismissed my previous suggestion to just use a properly sized single larger energy storage (battery,etc) , and implement this same feature in the eBike's software .. well .. that choice forces you to be more expensive , larger , and heavier .. when compared to someone who instead did implement the same function in one larger/better fit to application energy storage device (battery) , and used software. again .. if your want to avoid this price , size, weight increase .. than drop the intent to use a 2nd separate hardware energy storage .. or .. just accept the consequences (cons) of the choice to use a 2nd separate energy storage hardware.
My thoughts .. #1> 'high' is vague , I'm not clear on what specific amount you are thinking of , under what specific conditions .. #2> OEMs published specs are usually either a little on the optimistic side .. or cherry picked under ideal conditions .. or a combination of both .. #3> It isn't a black and white thing .. the harder they are pushed the faster they degrade .. That will include a combination of Charge Rate , Discharge rare, Temperature (high or low), CoC/DoD usage window , etc .. etc .. #4> Although 3 above (faster degradation) is very often the result .. Cell outright Failure is possible , and the harder you push a cell the higher the chance of cell outright failure .. so, if you intend to push it hard it becomes more important that you engineer into your application contingencies to safely mitigate such outright failure.
It will depend on the specific cell .. and the context (temperature, thermal management , duration, etc) .. not all cells are equal .. the best way to be certain is to do a test .. testing it under conditions that are harder/worse than the real world's worse case. I've seen some that are perfectly ok with sustained full cycle over 5C rates. such @ 96Ah x 5C = 475Amps I've seen some that are perfectly ok with bursts of a few seconds up to 20C rates. such @ 96Ah x 20C = 1920Amps But in the very cold (bellow freezing) all those rates drop down allot. The same cell that does ~20C bursts for a few seconds when warm (but not hot) .. might struggle to do more than 2C burst for a few seconds when it is down near ~0F .. some cells are designed/tweaked specifically to do a little better in the very cold, or very hot. And of course if you are ok with shorter useful life time .. like hundreds of cycles instead of many thousands of cycles .. well then you can beat on them a good bit harder.
The phrase 'duty cycle' .. for any battery (not just LFP) .. is the range of the battery that is used during application cycles of charging and discharging .. this is not a fixed thing .. there are pros and cons of different options that the system designer picks the trade off they are satisfied with .. for example a battery that has a duty cycle from 25% to 75% , has the pro of it would last a long number of such cycles/years .. but the con of not using 50% of the batteries maximum ability .. you had to pay for that battery in $ and in space and in weight , even if you don't use 50% of it .. if the same battery had a duty cycle of 1% to 99% , the con is that would not last as many cycles as the 25-75 , but the pro of using 98% of the batteries maximum ability.
What is going on with my battery pack? The label say LiFePO4, 54.6V, 576 Wh. It is 8p 13s, or 4.2V per 8p row. So it must be LiPo, not LiFe, right? The label on the charger that came with the battery says 48V2A Lipo. Why would they mislabel the battery, or is there some new chemistry that lets LiFePO4 charge to 4.2V per cell? Thanks, useful video.
I don't know the battery .. nor the company .. so I can't speak to why it's labeled some way , or why they did something. I can say the following though: #1> LiFePO4 charge to 4.2v per cell Technically any LiFePO4 cell could be charged to 4.2V per cell .. but it is exponentially more likely to result in cell failure .. and at the very least it will result in cell degradation / shorted service life (cycles/years). This is part of the end of charge .. when the terminal voltage goes exponential at the very end .. and the harm to the cell .. and the risk it causes is why most people never push a LiFePO4 cell any where near that hard (high of a terminal voltage). #2> Integrity of Label: If you doubt the integrity of the label .. than that in itself also puts doubt on anything the label say .. be it the LiFePO4 part .. or the 54.6v part .. etc. You could always check it directly .. calculate the nominal voltage under some known discharge load rate .. watch for the low end terminal volt rapid drop off point .. watch for the top end terminal voltage rapid exponential increase point .. etc ... once you have your own validated test data , you will be better able to confirm / refute/ etc whatever is on the label. If you directly verify for yourself that it is say 8p13s .. and you verify the voltage profile .. you can get a fairly good degree of certainty that way. It is also worth noting that mistakes do happen .. A company that makes multiple different kind of battery packs .. might have just accidentally put the wrong label on a battery pack. #3> Battery Labeled by intended market: It is not uncommon for battery companies to label a battery to a specific battery market .. ie .. labeling a battery as 12v .. doesn't mean you actually see 12v measured at the battery terminals .. it might only mean it is intended for a 12v battery market. Automotive 12v battery is a easy example .. the actual battery voltage varies considerably depending on SoC/SoE .. Temperature .. Load .. etc ... so even though it might not actually give you 12v .. it might still be labeled as a 12v battery ... meaning it is intended to be used in 12v battery market. Actual battery voltage varies widely depending on conditions .. SoC/SoE .. Temperature .. Rate of charge .. Rate of Discharge .. etc .etc. #4> LiFePO4 not specifically listed on the Charger: Like other members of the Li family ... LiFePO4 top end of charge safety termination can included watching the terminal voltage for the tell tale exponential voltage increase ... a charger smart enough to identify that shape .. Any Charger smart enough to do that can charge any Li Battery .. ideally with cell level monitoring or BMS .. but the end curve is the same shape for any of the Li family of batteries. However ... if the charger isn't smart enough to identify the end of charge terminal voltage shape .. and instead it just always goes to a specific CV set point .. say ~54.6v for example .. that isn't as (universally) safe for all members of the Li family .. because it could be way high for some batteries .. for example no 3s Li family battery should be taken to 54.6v ... but say 15s LiFePO4 pack would not be unusual to see a top end CV phase of 54.6v ... but 13s , would be really pushing the cells very hard (if they were LiFePO4) etc. I hope that helps some ... best of luck.
read above Being pink 18650 makes me think(99.9%) they are Samsung Li-ion...Being 13s8p makes me think this is 15ah li-ion battery...Also most all Li-ion are 13 series...Do not use lifepo4 charger with li-ion or vise versa...13s x 4.2v(li-ion)=54.6v or a 48 volt bank! test 1 row of parallel to see voltage when charged up...should be 4 or 4.1 Lifepo4 dont go above 3.7 volts!!! 13s x 3.6v(LiFePo4)=46.8v ,,,,,,Definitely your lifepo4 label is wrong I have several LiFePo4 batteries...They are all 22650, and they are all 16 series..10 ah,20ah and 40ah...My lifepo4 chargers charge at 60v/6a Because 16s x3.6v=57.8 volts...a tad heavier, but charge cycles and steady discharge make up for weight...Take care...
Thanks a lot sir! U Cleared many doubts of mine. Could you discuss a little more on d equivalent circuit design of d battery & explain d various resistances and d capacitor? Y r we still using LiCoPO4 in mobile phones instead of LiFePO4? Could u take a similar class for EIS studies of a li ion battery? Kindly provide ur maid id so that v can easily contact you sir. Thank you.
I am not the professor in the video .. I uploaded his video to my youtube channel for the benefit of others .. I am not clear on what your are asking about with regard to equivalent circuit, please clarify/describe more what specifically you are asking about ... As for your other question , why the industry doesn't currently use LiFePO4 flavors often in cell phones (and similar).. Batteries can be tweaked and modified extensively to better fit the specific needs of a specific application .. There is no 'one size fits all' , version of battery chemistry that would be the 'best' in every possible application .. While LiFePO4 could be used in cell phones, the industry uses other 'flavors' instead intentionally .. LiFePO4 is a 'safer' chemistry, but others already used for cell phones are 'safe enough', soo being safer than 'safe enough' has little additional benefit .. LiFePO4 can safely handle much higher rates of charge and discharge, but others already used in cell phones are able to keep up with the power needs of the phone (that application) , so unless a cell phone also has a built in tazzer or car jump starter feature there is little benefit for the additional power rates that other types like some of the LiFePO4 flavors could do .. For example the type of LiFePO4 battery I used in my PHEV conversion can safely handle bursts of charge or discharge up to 21C rates , that is almost 10x times faster than what Tesla BEVs can do, or what cell phones and lap tops can do .. but those Tesla BEVs, cell phones, and laptops instead have about 2x the stored energy .. it's a trade off .. Sense those other applications more benefit from wh/kg instead of w/kg they choose to tweak and use the Li flavor better suited to the specific application.
Oh I got it! Thank you ! Actually regarding my first question, I could not get d various electrical components u added to d electrical circuit , that is d ''resister'', d ''capacitor'', and d ''warbour resistance''. I wish to know d exact significance of each of d electrical component.
What do you mean by your use of the single letter "d" in your last comment ?? You put this single letter "d" in front of various different things in your last comment .. but "d" by itself isn't a word .. It might be a variable or reference to something else .. but right now I don't know how/what you are using that letter "d" for.
That's too broad .. please narrow down your question to something more specific. The 'exact significance' of each of those will depend on what you are referring to .. and in what application / context you are referring to. Also keep in mind this video is not intended to be 'exact' it is a basic overview .. like if someone was describing the basic overview of a car .. in general as a concept .. which is very different from 'exact' or 'specific' description of one specific car. For example: The resistance of external electrical load sink .. is not the same concept or significance as .. the resistance of a BMS's various resistors .. is not the same as .. the resistance of the power electronics .. is not the same as .. the effective resistance the battery itself has .. etc .. etc .. Same goes for capacitance, inductance, etc.. etc. Even if we narrow that down to just the 'effective electrical resistance' of a specific battery itself .. the 'exact' or 'specifics' , or 'significance' .. of that 'effective resistance' will change .. with different applications .. different usage situations .. different cell temperatures .. different SoE/SoC .. different rate of charge/discharge .. etc .. etc.
so... lithium cobalt is a cell phone battery, lipoly is fragile and catches fire easily if over/under charged, and lifepo4 is relatively safer than lipoly right? what is a general chemical makeup of lipoly, and what makes lipoly so dangerous at charge extremes? I'm guessing it has to do with cell voltages being closer to electrolyte breakdown voltage but that doesn't explain the problems with over discharge.
I'm not sure how in depth you want to get .. one can only say kind of general things with only general levels .. not all LiFePO4 are the same , anymore than all Lipoly are the same ... etc ... Generically .. Yes , the electrolyte break down is part , but so are the Anode and Cathodes loosing effective active material , and surface area as well ... The over discharge and high rates , are issues of unwanted chemical reactions .. Those unwanted chemical reactions can be dangerous .. or just shorten the total cell useful service life .. it can be in the electrolyte ... but it can also be in other parts of the cell.
What I cannot create, I do not understand. -richard feynman I'm originally coming at this from an rc hobby perspective and specifically I was looking at batteries from hobbyking.com. Once lipoly batteries are drained hobbyists treat them like bombs keeping them in special bags and charging $50+ for cheap Chinese chargers. Then I heard of lifepo4 batteries that are supposed to be safer. So I just considered buying those types of batteries. That's what has brought me here to this video. You have taught me a lot, thanks. I'm assuming some of this carries back to lipoly cells, but I'm having trouble finding the possibilities of what the electrodes could be made of to get even the foggiest of reasons why running a cell down to 1 or 2 volts can cause an issue. In your video you only mention catastrophic failures with lifepo4 with negative voltages on the battery(electrolyte breakdown and venting), but I think you only warn of lifespan issues with low voltage. Can you point me in a general direction of what lipoly could be made of and what kind of reactions could cause failure with over discharging?
At it's most generic .. The behavior you are asking about is a .. 'better safe than sorry' .. based behavior .. which is perfectly understandable and reasonable .. in a general/generic sense .. The cell chemistry is stable and functional within a certain range not higher than X not lower than Y .. SoC/SoE/Voltage/Temperature/etc .. There isn't a black and white line in the sand ... It's more like a shades of grey .. The further you go toward the ends of that 'safe' range .. or the further past it .. more of those unwanted chemical reactions are more like to happen and happen faster .. There have been cells that have been over discharged and still functioned fine .. but that becomes less and less likely the further they were pushed beyond the 'safe' range .. Most of the time when the cell is not taken far outside the 'safe' range .. the unwanted reactions just reduce useful cell life .. But there have also been batteries that caught fire , released toxic gases , etc .. Again it's shades of grey .. not a clean line at one single point. ... Lipoly is a generic term .. Battery companies can and do make them a number of different ways with thousands of different chemical combinations .. The name itself only tells you 2 basic / generic things .. #1> It's a Lithium reaction based battery ... #2> It uses a Polymer .. that's it .. that polymer could be a polymer electrolyte , just a polymer cell case ... etc .. the name alone doesn't tell you allot of details ..You can get some more detailed information about a specific battery by getting the 'Safety Data Sheet' for that battery .. Although they usually still won't easily disclose everything they use or put in that battery .. after all they don't want others copying them after they spent millions on researching and producing that specific chemical recipe .. Yes certain 'families' like LiFePO4 are 'safer' than other 'familes' .. but even than there are still thousands of possible variations among different battery companies .. Now generally speaking it takes energy to do any 'work' .. soo the unwanted chemical reaction from a battery with more potential energy .. high charge , high temperature, etc .. that higher potential energy content means that cell is more capable to do more 'work' .. good or bad work .. than a lower charge / temperature cell could .. but even 'flat' and 'cold' there is still potential energy content there.
It's all about the specific chemistries and constructions. The subject you want to research is "thermal runaway". When you short a battery (on purpose, by accident, or by misuse), there will be an enormous current flow. Because all batteries have some internal resistance, that means there will be heat generated. A lot of heat. Very quickly. Various LiPo chemistries have differing levels of tolerance to high temps. First gen LiCo is very well known for it's rapid, unstable runaway leading to "explosions" (albeit on the scale of a firecracker) and "venting with flame" :-) Second gen LiCo (NCA - NiCoAl) is slightly less prone to popping, but only marginally. (they're still firecrackers. This is the technology Tesla uses.) [3rd gen NMC is _much_ better] LiFePo has next to no thermal runaway issues. They can generate tremendous currents without damage. (which makes them popular with DIY EV car conversions.) Over-discharging leads to irreversible physical and chemical damage. This greatly reduces the cycle life of the battery, but does not cause them to "vent with flame". Rarely will this instantly destroy a battery -- so long as it's not "zero volts", recharged soon (or immediately), and you aren't making a habit of it. Manufacturers run tests and provide datasheets showing the charge/discharge lifecycle of their cells.
jfbeam thanks for explaining that. off the top of my head I was looking for something like how these chemicals are arranged in the anode/cathode/electrolyte/ or separator and what exothermic reaction is causing the problem
I do not (myself) have a 'white paper' on anything. I might be able to provide more assistance, if you can give me some more details about what 'white paper' you are looking for .. or , if not a specific 'white paper' , what specific topic you are looking for a 'white paper' on. Sorry .. a battery .. even LiFePO4 ones .. being charged .. is still very broad / general .. there are lots of aspects / parts of that.
@@ianpgeorge hi I am looking at charging technics of Battery Banks. I am playing around with charge circuit. I want to look into series configuration. I think Battery Management is very well understood but I believe there are a few hidden trade secrets. I am looking at LiFePO4 and Li-Ion chemistry.
Yes .. Battery Management itself is very well understood .. the exact hardware and software a given OEM uses to achieve that is often the 'trade secret' part .. for instance it is common to reduce charge rates into Li based batteries as they get colder and colder .. the exact electrical schematic and programmed algorithm that Tesla uses is a Trade Secret .. but it is well known to do such things. You need fairly well matched cells in the pack .. capacity, power , resistance , self discharge, etc. You need some passive fail safe measures .. fuse , vent , case, etc. You need some active protection (slow/stop @ top/bottom) , detect cell/battery fault, thermal management, etc. It is not uncommon for an OEM to 'tweak' battery chemistries for a specific application .. gaining item 'A' at the expense of reducing item 'B' .. which means , not all batteries even in the same group .. such as LiFePO4 , will have identical properties .. two differently tweaked LiFePO4 cells will be a little different from each other .. the power rates can be different, energy density can be different , self discharge can be different , etc .. the exact method of how they accomplish those 'tweaks' is often what are 'trade secrets'. Without knowing for certain the characteristics of a specific cell .. you can either just use 'generic' / 'general' criteria for that type .. it won't be as well matched to it .. compared to if you know that specific cells specific details .. sometimes the OEM publishes the performance / usage / application details .. other times you have to look for (or do) testing data in order to experimentally determine any 'tweaking' that might have been done to a specific given cell. For example I read through lots of published data on a few different 'tweaked' version of LiFePO4 before I picked a few to do another ~2 years of my own testing in order to gather more data on those specific 'finalist' cells .. before I finally picked the one specific 'tweaked' version I would use .. and then designed and fabricated the battery system for the car .. There are some parallels , but not all LiFePO4 are the 'tweaked' exactly the same... neither are 'Li-ion' , etc.
That (bellow 0C) is a commonly quoted thing .. but the chemistry doesn't actually work that way .. the (bellow 0C) thing is at best an over-simplification .. at worst just spreading incorrect information .. it isn't that simple or that black / white of a thing .. I touch on that topic in another video of mine .. perhaps you should start there. th-cam.com/video/DoyrKXvXSBM/w-d-xo.html
@@ianpgeorge Excellent thank you. I have seen datasheets that list -5C as the minimum charge temp. People will say things like don't charge "below freezing" but that correlation seems odd since no water is in the cell. I have also heard that you can charge safely if done at a reduced rate. Will check that video now, thank you!
@@thedillestpickle The speed of the Li ions slows down with colder temperatures, therefore the charge rate must go lower, too. Bad things happens if you try to recharge too quickly, when cold. Exactly how fast is too fast when too cold ??? So, they just say don't do it. But it can be done, just at a SLOWER recharge rate ...
I have a comment re LiPO4 over discharge. A 26.2 v 20 ah i had custom built for a project Evidentiary had a BMS that was defective or drew unreasonable parasitic current. During 7 months of storage the battery was ruined, not a single good cell. I tore a few open, and the dissolved replated copper from anode current collectors was obvious as a coppery sheen on the anode active material. Cell voltages were from 0 to 1 volt. $500 Down the drain. So beware of copper plating During over discharge. I later bought 16 LiPO4 cells to resurrect the project. I was Shocked that these new cells arrived with 0.8 to 0.95 volts. I thought they sold me garbage but i charged and discharged them and All were came up to stated capacity. So I'm confused. Can anyone tell me why the new ones were perfectly good and not copper plated?
To your post .. I would have a 5 part response: 1> All the bellow being said .. I would recommend you avoid going bellow 3.0v discharge on LiFePO4 cells .. to any significant degree on any regular rate .. there are significantly diminishing positive effects the further you go bellow that .. and at the same time significantly increasing risks of negative effects the further you go bellow that .. I am well aware there are many people who go well bellow that , they differ from me in their subjective opinion of where the pros outweigh the cons. #2> I suspect you are conflating correlation with causation : For example of concept .. If someone hears a rooster crow before the sun rises everyday .. they notice a correlation .. but the rooster crowing is not the cause of the sun rising. Noticing a correlation .. __ Substance inside a bad cell .. that doesn't necessarily mean that what you noticed happens to be the cause .. nor does it prove your theory of the copper dissolving and re-plating .. just because the new cells (you didn't open and test) worked, doesn't mean they didn't have that substance you noticed in the bad cell .. at present assuming it isn't there is just an un-tested theory. #3> I don't ( off hand) see a mechanism for your theory to have happened. "dissolved replated copper" .. as described in this video .. copper foil on the anode has graphite attached to it .. it is the graphite that is physically between the anode copper and the electrolyte .. Graphite does not dissolve copper foil (no mater what your BMS did) .. if the copper foil ever somehow got 'dissolved' (as you wrote) that would be electrically like cutting off the anode from any external device , no longer a electrical path to the world outside of that cell .. that would have prevented your BMS or any device (external to the cell) from drawing any current from the cell (ie would be permanently 0V) .. even if that were to somehow happen .. it only leaves another problem .. what changed in the chemistry inside this sealed cell to then extract that dissolved copper in order to do that 'replating' ... sooo ... I don't see a mechanism by which your theory of what happened .. could have been what actually happened inside the cell. Without more data to show otherwise .. I suspect you might have seen the copper foil of the anode .. not dissolved ,and replated .. just the anode is copper foil coated with a layer of graphite. #4> Potential difference in how it effects a cell to be 'driven' to a given voltage. When a new cell is made there is a (for lack of better term off hand) a 'evenness' , to the composition .. when you 'drive' a current (charge or discharge) .. you are seeing a 'macro' level net of numerous billions of molecular level interactions .. what this means .. is that if you 'drive' a cell to say 1v .. that 1v is the 'macro' combination of all those .. it is the net of all the tiny molecular level 0.9 , 0.8 , 1.1 , etc ... if a cell were 1st made with that same 1v , the deviation or internal 'spread' from that 1v is smaller , than if one got to that same 1v via charge or discharge. #5> There are significant benefits to initial 'formation' cycling. As described in this video .. as such .. if you get a 'new' cell that is (at rest) under 2.6v .. it is highly likely that whoever made the cell .. did not do that initial 'formation' cycling .. even if the cell works fine .. it would have worked better longer , if it had been correctly initial formation cycled.
@@ianpgeorge I was just asking a question and I thank you for your answers. But copper anode current collector dissolution during overdischarge is a well known problem in li ion cells. I respectfully suggest you do a little search on this topic sir.
@@davidpacholok8935Likewise .. I was just trying to answer/respond to your request of me. In this 2nd comment you reference Li Ion chemistry .. previously you were referencing LiFePO4 chemistry .. Please stay on the topic being discussed .. switching between different battery chemistries mid-conversation is not usually very helpful to achieve a productive dialogue .. apples to oranges and such .. yes there are some similarities (both fruit , both plants, etc) .. but generally speaking .. if you want to have a dialogue about LiFeO4 .. staying on the topic of LiFePO4 is usually helpful. You proposed a theory .. you provided no proof to support your theory .. I pointed out some of the potential issues I saw with your theory .. If you have evidence to site to back up your theory .. please , present that evidence .. if not ..oh well .. you just have a unsubstantiated theory. As far as I am concerned .. It is the burden of the person making the claim to provide the evidence to support their claim .. no one is by default automatically correct in anything they might claim .. the more extraordinary the claim made , the more extraordinary the burden of evidence on the one making that claim. Falsification .. finding the issues with a given theory .. is the bedrock foundation of all science .. IF you have a theory/claim ... science says you welcome and seek out the falsification of it .. yes men around you who only agree with you are not helping you .. if someone else finds a fault with your pet theory , that is a good thing. I am not perfect , nor omniscient , nor do I claim to be anything of the sort .. When someone comes to me (as you did here) asking me for my opinion .. I try to respond appropriately .. If something new is learned in the dialogue (by you , by me , or by anyone else reading it) .. great .. if not oh well .. I'm not perfect , I made an honest effort .. that's all anyone can do.
wow so there's graphite in the batteries I guess it's like Chernobyl if you suspect something happened to your batteries while you were away and you find graphite on the ground you know something bad happened.
I have not watched all of it, but isnt the elephant in the room that discharge charts have no bearing on EV reality? They assume a motorist uses a constant rate of power. Rot of course. Its hugely variable. Which begs the question, "How is the chemical reaction affected by varied use?" Clearly any heat issues would be far less for short bursts than for constant high C rates. Intervals of low c-rates may yield a buffer of extra discharge capacity for bursts of high C-rate use? Surely more real world discharge simulations are called for to better evaluate suitability to task?
That is not the elephant in the room .. Your base assumption is that the varying load test is not done .. that is not a necessarily correct assumption .. Sure some individuals don't do rigorous / detailed testing like that .. but some (like me) do .. You are correct it can give more information / validation on how a given battery will behave under those conditions in the real world .. Which is part of the reason why I did it .. For example I did numerous variations in my own testing ... I varied charges and I varied Discharges ... some were constant current , some constant power , some constant voltage , some set energy pulses .. some were not constant anything, and varied over a programmed test sequence , some at various different levels of SoC / SoE charging , some at various different levels of SoC / SoE discharging ... etc ... etc ... by me doing the additional testing I have more data .. thus I already have a better evaluation than someone who would only do a more limited / simpler type of test or tests.
More like EV reality(Tesla) needs to catch up to smaller, lighter, urban vehicles like the whole world is introducing right now, that love these low speed, high charge rate, safety, dependability and green factor...Much cheaper than Lico will ever get, and better to recycle...There are also many better Powerwalls now that use this technology, going away from high density LiCo...
It's your life , do whatever you like .. but .. just so you know : #1> AGM is almost always , only cheaper on short time scales .. in the long run (10-20 yrs +) AGM is almost always ends up being far more expensive than similar performing LiFePO4 options. #2> For most applications/people .. automated battery monitoring / management is proffered .. Even those who use AGM often use automated systems .. prevent over charging , prevent over discharging , etc .. thus it ends up making no difference to the user if it's AGM with automated systems , or LiFePO4 with automated systems .. either way .. the automated systems (once configured) do their job.
Ian George... what are you talking about? Smart chargers charge AGMs near perfectly with no monitoring. It is a set it and forget it type deal. Used AGMs can probably "hang" with or beat LiFePO4s over your 10 to 20 year period. I might need 2 or 3 sets of used AGMs during that period but if they cost 1/4 of the cost of your 10-20 year batteries (I assume new), then your statement will be wrong. Would you like to compare real world prices of good used AGMs vs 10 to 20 year LiFePO4s? I am up for the challenge. I have an advantage because my old AGM batteries have scrap value so a 100 pound AGM has a value of $20 so if it cost me say $75 originally, the real cost (to use it all of those years) is only really $55. This is just an example, not the real prices. Also, in your #1 point, that assume that the user of the LiFePO4 batteries knows what they are doing. If they make a big mistake, they could easily damage them. For example, if someone cuts corners and doesn't balance them often. Your #2 point is not very accurate either. Almost all inverters I have seen (which are frequently used to discharge batteries), have built in low voltage protection. Generally under load, the inverter will NOT let the batteries drop below 10.5V per 12V of nominal voltage. How the hell then are you going to over-discharge the batteries then??
You made allot of different claims .. soo .. my response will be a little lengthy in order to cover what you wrote. I will put "---" as a means to try and identify sections addressing the same concept. --- The smart charger is the same to effect to both .. that is the same as The #2 I previously listed. You describe using a smart charger to automate the monitoring of the AGM .. someone else uses a smart charger to automated the monitoring of the LiFePO4 .. net result in both cases is the same .. set it and forget it .. the automated system does the monitoring for you .. With actually zero monitoring (nothing stopping over charge, or over dis-charge) the AGM can die pretty quickly .. That is why automated systems (that make it set and forget) are more popular for most battery applications (AGM , LiFePO4, etc) --- Used product comparisons get tricky .. like a used car .. the condition / value / deal .. one person got one time .. gets can vary significantly .. it has much less to actually do with the actual battery chemistry itself .. and more about the 'hand' the person happen to be dealt .. maybe the used AGM (or LifePO4) happen to be a bad deal next to dead (it has happened to people) .. or maybe they are great conditions / a great deal (also has happened to people). --- Your claim about my statement.. "then your statement will be wrong" .. is itself incorrect .. My statement would not be wrong , even in the situation in which you described .. I did not make an absolute statement .. I didn't say it was impossible .. I claimed .. "Almost always" in #1 .. and "Most applications" in #2. Just like pointing to one lottery winner doesn't change how unlikely that is to happen .. or in this case describing an imaginary hypothetical lottery winner , also does not change how unlikely or likely it actually is to win the lottery in the real world. After all .. a made up an imaginary hypothetical example .. if that were possible (and I think it is) .. all that shows is that it is hypothetically possible .. it says nothing about the frequency or distribution of it in the population .. and .. I too could just as easily make up a different imaginary hypothetical example with different results .. and it too would also have no effect on the frequency or distribution in the real world population. One off examples (even if true) don't make a good case for anything .. and luck of the drawl one gets with the condition of used batteries (AGM or LiFePO4) is not really about the battery chemistry itself , it's like buying a used car .. some are lemons some are diamonds (it happens to people sometimes). --- Also don't forget .. battery application performance is not just the cycle life of the battery itself .. your AGMs are less cycle efficient .. and have larger self discharge .. and have lower power density .. and lower energy density .. etc. For example: If AGM used in solar / wind /etc .. you have to pay to install more kw of solar/wind just to get the same kwh of energy out of them to use .. and they wear out much faster. If used in any mobile application .. Scooters, RC , HEVs , BEVs , etc .. AGM seriously reduces usable range , reduces usable power , increases energy per mile cost , wears out faster , etc. --- As for your comment about " knows what they are doing" .. That applies equally to both AGM or LiFePO4 .. the person who doesn't know what they are doing .. is able to kill either one .. or any battery for that matter .. thus .. that too .. has virtually nothing to do with the battery chemistry itself. --- Your claim "Your #2 point is not very accurate either." ... In what way ? .. Please elaborate specifically on what is inaccurate ? .. I don't see any part of your comment describing an actual inaccuracy in the #2 point I made above. --- In response to your question .. "How the hell then are you going to over-discharge the batteries then??" I'm not sure why you would want to .. but .. if the automated monitoring system you are using is only looking at the whole pack for that low voltage point 12v or 10.5v .. it actually isn't all the hard to over-discharge like you asked to do: For any battery chemistry (AGM, LiFePO4, etc) .. off the top of my head : OptionA> If the series cells that make up the battery pack in question are not well matched.OptionB> If the series cells that make up the battery are not well balanced. OptionC> If there is an uneven load across the series cells. OptionD> If the rate of attempted discharge (Watts or Amps) is too fast for the battery's present condition. OptionE> If those voltage points 12vor 10.5v are not correct the specific battery connected to. In any of those A-E examples a 12v or 10.5v low voltage cut off can still result in a over discharged battery .. be it AGM , LiFePO4, LTO , NiMH , etc.
Many of your "defenses" here can be easily challenged. You mention power density but how is that a yardstick of performance? If I have an AGM battery bank with 5 KWh of usable power (down to 50% state of charge) and you have 5 KWh of usable LiFePO4 power (down to say 20% state of charge), you might have a higher power density but we both have 5 KWh of usable power so who cares about power density? You mention 5 options (A thru E) of possible ways to overdischarge a battery bank with references to series connected cells. An easy way around those issues is to just parallel connect 12V batteries. For example, I could use a 12V 100Ah battery in parallel with a 12V 33Ah battery (both AGM) and if done correctly, they will both drain about equally (down to 50% State of charge for example). The combo will have MORE power than just the 100Ah battery alone. Option D is exceptionally wrong. There is actually a flaw in the 10.5V cutoff in many inverters, however this flaw is more pronounced if the load is too small, not too large. Your description stated you can possible over discharge a battery bank if the discharge rate is too fast for the battery. That is actually backwards. If the battery is old and tired, it will immediately complain about the heavy load and likely dip below 10.5V, thus shutting off the inverter. If the load is high on a healthy battery, it will likely do it for a while, then shut off the inverter MUCH quicker than if there was a very light load, and then rebound back to a MUCH higher voltage such as 12.0 or even higher.... The problem comes in when there is a very light load on an inverter. That is because 10.5V low voltage cutoff with a very light load will actually put the battery bank in an over discharged state. This is the actual case when "automated" protection can actually fail but you did not mention this one. For example, imagine if I used a small 12V inverter and the only load on it was the inverter itself (let's say 6 measured watts which mine tested at), and a 0.5W LED nightlight (a valid test). That setup will drain the battery bank to a MUCH lower state than some heavy load of say hundreds of watts. This is because there is less voltage sag under load and thus less voltage "rebound" after the load is removed. Try it sometime on an old AGM battery not worth much. The 10.5V might spring back to 11.8V for example and that is bad since it is below 50% state of charge. That same battery with a heavy load would likely spring back to 12.0V or more. This is a flaw of many inverter low voltage cutoffs. They should NOT go by voltage alone (such as 10.5V) but rather a function of both voltage and load. Under a very light load, the cutoff should be more like 11.0V or maybe even higher. This "table" of load/voltage combinations should be part of the cutoff and referenced in real time.
As before .. you had many items for me to respond to .. so this will be a little lengthy .. again I used "---" to try and identify groups / or sections. --- Power density is one of the metrics which battery performance is measured .. all over the world .. you don't have to like it .. but that it is one of the real metrics of battery performance that is reality .. no matter what your personal opinion about it is .. we can discuss some of the reasons why it matters more in some applications and less in others .. but in the end .. if you personally choose to disagree (that's fine it's your life) , but the rest of the world won't care .. and power density will continue to be one of the metrics which battery performance is measured. --- That having been said .. you also seem to be confusing / misusing some of the concepts being discussed .. so (for the sake of anyone else whoever reads this) I'll start there clear up a bit , and work my why up. power and energy : Energy (calories , wh , joules, etc) .. is the capacity to do work .. if you want to move a stationary object .. or stop moving a moving object .. either would require energy .. if you want to change the temperature of an object up or down that also requires energy .. etc .. etc. Power (watts , HP , BTU , etc) .. is the rate of energy per unit time .. how fast is the energy being spent , consumed , etc. .. what this means is that .. 5 kwh is a measurement of energy .. it is not a measurement of power. ---- Next Density (Power or Energy) Density of either power or energy can be measured either .. by volume .. or .. by mass. power density by volume might look like Watts / Liters power density by mass might look like watts / kg energy density by volume might looks like wh / Liter energy density by mass might look like wh / kg Therefore: A battery with lower power density by volume .. will need more space to be able to supply the same total watts of power. A battery with lower power density by mass .. will need more mass (weight) to be able to supply the same total watts of power. A battery with lower energy density by volume .. will need more space to be able to supply the same total Wh of energy. A battery with lower energy density by mass .. will need more mass (weight) to be able to supply the same total wh of energy. --- Next .. to finally get to answer your question "who cares about power density?" In my last response to you .. someone reading what I wrote in close detail .. might notice .. I gave two different examples of concept: A stationary application (solar/wind/etc) .. and .. A mobile application (Scooter,HEV,BEV,etc) .. these different applications care differently about power or energy density. Usually .. Stationary applications don't care as much about space or weight costs .. it still matters .. the client only has a fixed sized room available , or the floor under it is only rated for so many kg of weight , etc .. but usually it matters less than it does in mobile applications. For example take .. 5kwh of usable energy mentioned above .. with enclosure , wiring , etc. AGM version .. might end up weighing around ~800 Lbs. LiFePO4 version .. might end up weighing around ~120Lbs. In the vast majority of mobile applications .. such as HEV, BEV, etc .. moving ~800lbs instead of ~120Lbs .. for the same ~5kwh of available energy .. the lighter is much better , because it will eat less of that 5kwh to move .. thus it will have a longer range from the same 5kwh of energy .. which will also mean it will be more energy efficient and cost less to fuel it per mile traveled .. it also means the heavier vehicle will have less net acceleration , as more of it's motor power is spent moving the extra weight .. and that means it don't be able to climb as steep of hills ... etc. Now in a stationary application it might not matter as much .. for example that ~800 Lbs in some places (like the roof) , might not be a good idea .. many other locations (like cement floor) will have no trouble with supporting that weight .. so the stationary application still cares .. and the vastly heavier battery still has a con to it's much higher weight .. even if it isn't as much of a con as it would be in a different application .. but either way .. it is still a metric used to evaluate the performance of the battery in the application. --- Responding to your : "You mention 5 options (A thru E) of possible ways to overdischarge a battery bank with references to series connected cells. An easy way around those issues is to just parallel connect 12V batteries." no .. your suggestion will not 'get around' any of those 5. 1st one has to understand .. there is no single cell battery chemistry in the world that gives 12v .. a so called 12v battery is itself (internally) a group of multiple battery cells connected in series .. The voltage profile for AGM would require 6cells be put in series to get a 12v AGM battery .. the voltage profile for LiFePO4 would require 4cells be put in series to get a 12v LiFePO4 battery. The paralleling method you describe .. is effective for paralleling individual cells .. but .. wired as you described .. series 1st to get to 12v then parallel afterward .. that wiring method will not allow the paralleling method to offer any protection to the battery cells that were 1st wired in series to get the 12v. Bellow is an Example .. of a AGM battery wired as you described .. but can still get over discharged if pulled down to a net overall 12v or 10.5v. Of the 6AGM cells wired in series .. needed to get to that 12v .. what if .. 5 are the 100Ah you listed .. but 1 of those cells is is only 50Ah .. all 6 together in series still give a 12v battery .. but when you try to pull all 6 together down to just ~50% target you listed .. you pull 50Ah from all 6 cells .. well one of them only had 50Ah total .. it just got pulled down to 0% SoC .. And while that one cell's voltage drops off .. the other 5 cells in the 6 series pack all still have voltage. We can do the same if we had 1 of the 4 LiFePO4 significantly lower capacity than the other 3. thus .. all 5.. A-E methods would still work .. although I still don't know why someone would want to do so. --- Responding to your : "Option D is exceptionally wrong" You described a 100% perfectly valid additional way it can happen .. adding 1 more to the list .. up to 6 ways now with your Option F .. although .. I still don't know why someone would want to do so. I also think you misunderstood the part of that comment of mine where I wrote "for the battery's present condition" The rate of power watts .. or the rate of current amps .. that is 'safe' , ie not harmful to a battery .. depends on the batteries present condition. For example .. a battery very cold .. is different from a room temperature battery .. just like a very hot battery is different from a room temperature battery .. or a unmatched pack of batteries is different from a well matched pack of batteries .. or a unbalanced pack of batteries is different from a well balance pack of batteries .. etc.
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This guy is a genius at explaining batteries. I wish I could hire him as a consultant
One of the most educational videos I've ever seen.
One of the best explanation of how batteries work on TH-cam is on a whiteboard with sharpie, a job done better without animations. Every sentence was meaningful, a thorough illustration.
And good news. Supercaps are cheaper now.
Very informative, and extremely well-presented! Applicable knowledge delivered in a manner to be understood and used by novices and professionals alike. Thank you very much for making this available!
Wow, that was amazing! Prof Whitacre is incredible and I love the work he does. The presentation was top notch. Ian, this was the channel I've been looking for :)
Brilliant simple explanation of complex system Ian. Many thanks!
Very clear and informative, not only about the theory but also the performance and service implications. Thanks!
If I ever need an obsessed battery scientist to save the-world, this guy is it.
Thank you, so much, for posting this!
I now understand why my plug-in hybrid car has/needs super capacitors and why it makes that whining noise when the engine starts and why that noise tapers off over time. And, he wasn't even discussing that. But, the information he provided on discharge curves that contrast batteries with super capacitors in regard to total available capacity filled in the "blanks" for me.
This is an excellent tutorial.
Fascinating stuff. I’ve put it in my “favourites” for reference. . . It’s interesting to see how far we’ve come in just 5 years, with respect to cell cost. . .
thanks for the upload and Prof. Whitacre explained the details eloquently
Awesome stuff. Ready for this to take over the battery world. Its great to hear someone talk about batteries that really understand the subject.
Wow this is fantastic! Some over my head as an electrical engineer but he helps me catch up. Love this discussion and trade offs with this tech.
Incredible session! Thanks for posting this
Thank you Ian! I have been looking for this video since viewing it years ago.
Watching this video was an hour very well spent!
Fantastic... Really helpful and some interesting inside information!
This is an incredibly useful talk!
...
49:55 A little about battery care, temperatures, electrolyte decomposition.
50:19 LiFEPO4 charging, maximum charge voltage 4.3V, temperatures, battery stability, safety issues.
53:50 Optimal location of temperature sensor on LIFEPO4 battery cell/pack, sensor fuse, not on plastic case but on the elektrode metal bar!
55:20 Overdischarge, below 0V discharge,
58:00 Outside cell temperature, deep inside temperature, monitoring issues.
1:00 Very low temperatures, much more below 0C, -60C...-50C depends on chemistry!, freezing LiFEpo4 batteries in liquid nitrogen.
1:03:00 Discharge 2C, A123 Systems, battery cells in series, BMS, LiFEPo4 batteries from unknown soures, battery pack management costs.
1:-4:00 Cells in string must have the same capacity to lower maitenece costs! The same state of charge
Great Info Video, I was well Informed on the LiFePO cells..
Wow, so much great information in there explained so well. Thanks! :)
Fantastic, a great insight into Li Ion batteries. ThanK you for sharing.
Stocked to see this video is still available.
Very informative learned a lot thanks
Just found this. Awsome!👍
Amazing information!
You got a new subscriber.❤️
EXCELLENT .... Thank thee for sharing this.
Great .A lot of knowlege in your video.
Thanks for waking me up
Excellent presentation! Thank you! I'm wondering - can you recommend a reference text book that has the info you presented here?
This was so helpful for my Paper, words can't even describe it. Thanks for uploading :)
Did he ever give the talk on supercaps? That would probably be equally as fascinating to watch!
Greetings from Germany - Mo
I don't know (although I suspect that he did do so) .. This is the only one of his lectures / talks I have a video of .. However , I have little doubt over his many university years in that field , that talks on supercapacitors came up many times .. I just don't have a video of it myself to share.
@@ianpgeorge yeah, i didnt geven get my hopes up, and even so, just this video is pretty amazing :)
Great informative video, one thing iam not sure was covered was
How important is it to get these LiFePo4 batteries discharged from full charge to a 1/3 or 1/2 charge state while in storage.
God bless you, sir.
First, this was wonderfully insightful. I'm just an EE working in software but the level was exciting to know I was able to follow along with my old school training. :D
Second, what manufacturer did you go with? If Thunder-sky, did you find they were consistent on that last plotting? I'm considering them for a home application.
I personally used A123 as a brand of LiFePO4 .. From I've heard Thunder-sky versions are easier to work with (block instead of pouch , and screw terminals instead of tabs), and they are only a little less in terms of energy and power density compared to the A123 Pouch/Tab cells .. Best of luck.
Excellent video very helpful. Is there a video of him discussing super caps?
Not exclusively super caps that know of.
Very very good presentation !! LFP BATTERY getting more attention as TESLA start using them in model3 may be can you share information in advance in LFP battery ??
I am now a LIPO expert...thanks...
Hi Ian, thanks for uploading, great video overview. I was wondering if you have any suggestions on any test books that are specific to lifepo4 cathode and anode design and cylindrical call manufacturing? I have come across a few online but as they are pretty expensive I would love it if you could recommend one.
You're welcome.
I do not have any such suggestions to offer.
Ian, Guitartec here again with more questions... As I mentioned before, I run an on-line escooter club, so your answers may be posted there, if that's okay? So far, your explanation on LiFePo care and maintenance has been super helpful. A few more questions have been raised that I thought I'd send your way, if you feel like answering?
#1 Do LiFePos need to ventilate? We understand getting a lithium battery wet is a big no-no, but what about allowing it to breathe? These are 18lbs Chinese-made LiFePo batteries in a hard plastic(?) box wrapped partially in factory heat shrink. The US distributor suggests sealing them further in plastic wrap to ensure dryness, however, the only holes into the casing that are visable are where the grommeted charging and main wires exit the casing. These holes may also act as air vents- we aren't sure. So we'd like to know if sealing the holes up with silicone would cause some sort of gas build up?
#2 is about LiPos with 18650 cells. If a few cells go bad prematurely, can they be repaired and rebalanced again? I guess the same question goes for LiFePos, unless a drastically more complex answer is needed.
Thanks in advance for any insight you can provide.
I don't mind my replies or comments being re-posted.
#1> LiFePO4 ventilation
During normal operation this flavor of battery chemistry has no need for .. nor any benefit in 'breathing' or 'ventilating' .. It's a sealed (water tight and air tight) system .. and when operating correctly should never 'vent' any gasses or liquids.
The design intent for allowing ventilation .. is not during normal use .. but to mitigate the potential hazards in case of catastrophic battery or cell failure.
If the battery cell has a catastrophic failure .. it can potentially rupture and release both toxic and flammable gasses .. Under those conditions , venting those released gasses can reduce the potential risk during that cell failure / rupture situation .. but that is the only situation such venting is used for .. soo it would be useful / beneficial in that situation .. but not in any other.
The cell itself should be water and air tight .. and in a electrical isolating material .. the only external battery cell location you want to actively avoid getting wet .. is the + and - terminals .. for the same reason you don't want any bare electrical connections getting wet .. ie don't spray your garden hose at the live main electrical panel in your house .. bad idea.
The bad for Li to get wet you are referring to .. is the chemical insides of the battery cell .. as long as the cell remains sealed .. this should not ever come up in normal operation .. it is only something to be mindful of in case of catastrophic cell failure when the cell ruptures and an opening is created that could allow water to get inside the cell .. say for example during a catastrophic cell failure , the vehicle catches fire , or even the battery pack itself catches on fire ... normal water should not be used ro put out that fire ... because it's bad to spray water into any live electrical circuit .. just like you would never spray water at a fire on the main electrical panel in your house .. bad idea .. and (in the case of the LiFePO4 Battery) because of the potential for the water to get inside a ruptured cell ... thus fire extinguishers that use a dry or (non-water) foam extinguishing agent and that are rated A, B, C .. should be used to put out such LiFePO4 Battery fires .. not water .. such fire extinguishers are readily and easily available in a variety of sizes .. keep in mind .. in the event of a catastrophic battery cell failure .. The battery can potentially 're-start' a fire , until it has used up all it's internal chemical potential energy .. soo even if a fire is out .. such a catastrophically failed battery should be treat with caution.
#2> Reviving 'bad' cell.
Depends on how and why it went 'bad'.
Some yes .. some no.
If the case ruptured .. vented some gasses from the inside , or leaked some liquid electrolyte form the inside .. no .. battery is a hazard and needs to be properly disposed of / recycled.
If 'bad' as in a given cell is out of balance .. or no longer well matched with the other cells of the pack it is in .. than 'yes' ... that cell can be re-balanced with the other cells of it's pack .. and/or that cell can be re-matched with other cells in a pack re-selection / re-build.
etc ... etc ... it depends on the specific details of what kind of 'bad' one is referring to.
Ian, thanks! This is great stuff. Let me post this and see if anyone has any response questions. May take a few weeks. I'll get back to you. Guitartec (Dean)
well explained ,
Great video! Hope to see more from you. We want to replace a stand by battery system 100KW currently built with VRLAs. We'll connect 3 battery trays of 11 or 12 TSWB-LYP200AHA cells in series to make a battery set of 108 V. Each battery tray of 36V has its own BMS. Each battery set has a diode in series and its charged by its own battery charger. In normal conditions the battery charger 25KW will feed the loads on the DC108V bus and when power is OFF we switch to the battery power. Has anyone tried this? Will it work if we have 4 of these battery sets in parallel?
great video on LiFePO4 cells. Thanks. Is temperature increase happen only during discharge? Or will it happen on charge. How to improve the temperature increase during charge. I see mobile phones heat up during charge also
Temperature increase happens on both charge and discharge .. however, not exactly the same .. Mobile phone batteries are chemically very different than the LiFePO4 being described here , there are some similarities but there are numerous differences .. Improve as in 'reduce' the amount of heat increase during charging .. AC charging heats less than DC charging .. or charge slower .. or increase / improve the heat dissipation system .. or add storage in the form of some thermal mass, the most weight efficient of such are phase change compounds.
Thanks
Can any one recommend a good book about this topic: LiFePO4 please? I really liked this video. It gave me a good overview of that element that form time to time I implement in my electrical designs but I don't comprehend much. Thanks!
Sorry , I don't know off hand of a 'book' , specifically about LiFePO4
... although there could be a market .. if someone wanted to compile
such a text .. There are lots and lots of technical papers on various
parts , aspects , and different applications , and treatment of the
chemistry.
Thanks for uploading this Ian, great talk - can you tell me the name of the presenter?
June 2010 Professor Jay Whitacre
www.cmu.edu/engineering/materials/people/faculty/bios/whitacre.html
I'm am at the point of deciding between batteries for my EV (electric motorcycle) . On the top of the scale is the LCO, on the other end is LTO which is the least energy dense but safest. Lifep04 being in the middle of the 2 chemistries in terms of energy density and safety. Would you you say lifep04 is still a good choice for an EV?
To directly answer your question .. I would say .. Yes , in some EV applications a given LiFePO4 battery can still be a good choice .. I would even go so far as to say .. Yes , in some EV applications a given LiFePO4 battery could even be the best possible choice .. but not all LiFePO4 are the same .. and not all applications are the same.
.. That being said .. a few other aspects worth noting.
LTO and LiFePO4 are not mutually exclusive things .. one refers to the anode the other to the cathode .. it is entirely possible for the same battery to be both LTO and LiFePO4 at the same time.
.. That being said ..
You would have to define what your priorities are for the EV you you designing / building .. what those priorities are is up to you .. if by 'top of scale' you are referring to energy density .. LCO is not top of that energy density scale .. There are other rechargeable battery options that have higher energy densities , the highest I've ever seen in use is ~500 wh/kg .. but .. as you alluded to .. there is no one battery that is best at everything .. it is always a question of trade offs .. +1 here -1 there .. thus a question of your application priorities .. in some EV applications I could see LCO , LTO , and LiFePO4 all 3 of them being a bad choice .. the devil is in the details of the application.
.. My advise ..
Just sit down with what your application needs the batteries to do .. power density (charge and discharge) , energy density , operating conditions (temperature, mechanical stresses , etc) , Expected service life cycles/years , budget , limitations of other components you've already selected 9for one reason or another , etc .. once you have all that .. then walk through each specific battery option and see how each one fits your various priorities .. run through the numbers and see how each option would reasonably be expected to perform in you application.
Could one charge each 3.4V cell and cycle it individually and then when recharged set it aside and do this for each cell for the pack. Then hook them all up in series when they have the same state of charge and use them... or maybe hook them all in parallel and cycle the set ... and these would "balance" the cycles or valus?
I would recommend keeping in mind 3 things :
#1> balancing is not the same as matching.
matching is putting together cells as close to identical twins as possible.
balancing is putting together cells as close to the same instantaneous SoC/SoE as possible.
#2> There is more than one type of balancing.
A top balanced pack might be very out of balance at the bottom.
A bottom balanced pack might be very out of balance at the top.
A middle balanced pack might be a little out on both top and bottom.
etc...
#3> Cell Drift
Without some type of external system to make adjustments over time .. cells in series usually naturally tend to drift apart (become unbalanced) over time / use / and changes in temperature .. the closer the 'matching' the pack cells are the slower it will happen .. but .. no matter how well 'matched' initially .. no matter how well 'balanced' initially .. eventually over time they will eventually drift apart and become unbalanced , and less matched .. a well matched and well balanced pack (with reasonable type of use) should take several years to drift any significant amount.
This is the guy that set up the Battery business aquion Energy with the salt water Battery...
that didnt work out so well.....
Electron from the cathode side during charging is not from lithium. The electron is from the Fe(+2) as it changes to Fe(+3). That's the reason why one uses transition metals for cathode.
Perspective and Context are important:
Your comment = describing mainly outside the battery
The difference between electron flow and current flow.
Because electrons are negative sign (not because of transition metals) .. electrons flow opposite the direction of the current flow .. soo a +flow of current into the battery .. or into the capacitor .. or into the fuse .. or into the light bulb .. or into a wire .. a +flow of current into anything .. that means an opposite direction flow of electrons out of it .. that is just a product of the convention that we give electrons a negative sign in the same conditions we give current flow a positive .. electrons flow in the opposite direction as current .. that's just convention.
different perspective and context than
This video is mainly describing inside a LiFePO4 battery cell:
From a inside the battery point of view / context .. anode electrolyte cathode .. of a lithium based battery .. it very much is the lithium ion that is the charge carrier that flows into and out of either the anode or the cathode through the electrolyte , during charging or discharging .. electrons themselves are NOT the charge carriers inside the cell that move through the electrolyte and into or out of either side anode or cathode during charge or discharge.
The true whole picture includes both :
Inside the cell perspective / context where lithium ions are the charge carriers moving into or out of each side (anode/cathode) through the electrolyte between them .. and .. the outside the cell perspective / context where electrons are the charge carriers that move into or out of each side (anode/cathode) through the wires we connect to those terminals.
@Ian George Thank you for your answer.
But my comment was about your explanation at 8:12.
You explain that the electron flow out from the cathode during charging is by stripping off an electron from lithium atom, not from the Fe(+2).
As far as I know, the lithium atom in the cathode active material is cationic, not neutral. The phosphate anion stabilizes both of the lithium ion and Iron (+2).
If the lithium acts as neutral in the cathode active material, then the battery can't provide 3.2V.
That's the reason why we should use transition metal for cathode active material which can provide electrons during charging.
@@techtripkorea You are welcome.
I (Ian) do not appear in this video at all at any point .. as I wrote in the video description ... Speaker is Professor Jay Whitacre (that is not me/Ian).
Your description of the video is not accurate .. re-watch it if you like .. What Professor Jay Whitacre says at the 8:12 you reference is and I quote .. "I am stripping electrons from my LiFePO4" .. at that point you reference in the video , he is not specifying what part of that LiFePO4 compound gives the electron that exits the cell out that terminal (flowing out opposite direction to the flow of charge current).
It might help to think of it like dominoes the Lithium doesn't have to be the 1st initial source of the electron that leaves the cell out of the cathode during charging , but ultimately the lithium is the last one left in the chain to give up an electron at the cathode ... the last thing that lithium does, when it becomes and + charged Lithium Ion and then that Lithium Ion leaves the cathode.
It is only as a + charged Lithium ion that it (the Lithium) then travels (diffuses) through the electrolyte , to get to the other terminal (anode) .. while charging strips electrons flowing out of the cathode .. at the same time charging is adding electrons to the anode .. those additional -charge electrons building up on the anode (during charging) attract the +Li ion that left the cathode (when it gave up it's electron to the remaining components making up the remaining cathode compound).
Ian, As I'm writing this, I just realized that LiFePos could come in 18650 cells- insert pic of me with face in hand.
I was just sent a pic of an eScooter member's 2015 48V LiFePo battery that has the shrink wrap removed. This is the battery from my last post that has some damaged cells he wants to repair and rebalance.
The pic shows 104 pink 18650 cells (13 rows x 8 cells in series). The label cleary says it's a LiFePo battery, but (until a second ago) I thought all 18650 cells were LiPos. The reason is, every LiFePo I've ever seen torn down consisted of alternating large plates with separators, not individual 18650 cells. I guess there's more than one way to build a LiFePo. The question is, is one style better than another regarding high voltage scooter batteries?
The spec label on his battery reads; Max Charging Voltage= 54.6V, Max Charging Current= 10A, Continue Discharging Current= 25A, Peak Discharging Current= 50A.
If for some reason you suspect this isn't a LiFePo, which is what I did, please let me know.
Thanks, Dean
I would say better for specific applications / conditions .. yes ... but one way , better for all possible different applications / conditions .. no.
Look at the pros and cons of each method .. look at the conditions it will be exposed to in the given application.
For example Plates & separators can add additional pack rigidity , and additional pack isolation in case of catastrophic cell failure , it can help with the modularity of pack design , etc .. but not all applications equally care about such things .. the plates and separators add additional volume/space , weight , cost to the pack .. in some applications the pros of plates and separators outweigh the cons .. in other applications the cons out weigh the pros and they aren't used.
There is also variation in the battery design even in the same chemistry .. make the conductive anode/cathode thicker for reduced resistance , and better high current abilities .. but doing so gives up some of the space and weight for capacity .. etc.etc.
If you verified that on charge it goes into the exponential terminal voltage shape near ~54v .. not that it entered that long before / lower voltage .. If that Exponential terminal voltage under charge shape shows up at ~50v .. or down at ~45v .. that's the point to note , without continuing to drive and push it to ever exponentially higher voltages .. not what the label says .. what does the battery do under charge ?
If you've opened it an verified the connections are 8s that would make the ~54.6v very odd ... 54.6 / 8 = ~6.825v per cell .. that's not right ... if you verified 13s connections .. 54.6/13 = ~4.2v per cell .. Depending on the charge rate .. you should see the terminal voltage on LiFePO4 start going exponential around 3.5v-3.6v per cell .. the higher the charge rate the higher the terminal voltage point at which you reach that start of exponential voltage shape .. but 13s connections of LiFePO4 cells would definitely go exponential long before 54.6v .. 54.6v would be conventional for LiFePO4 used on a 15s pack.
Best way to know is to verify some things .. verify if it is 13s or 15s .. what the charge voltage curve , under some known charge rate .. when does it start to go into that exponential voltage shape ... etc .. than, completely separate from the label , you could verify and be fairly certain about the what the battery is .. whatever that is.
Thanks Ian, I have to admit, I understood your first 3 or 4 paragraphs, and I totally appreciate it, but the diagnostic stuff is a bit over my head. Even so, I'll pass on the info. Maybe the owner of this troubled battery will understand it more than I. I'll let it sink in, too. Thanks as always for sharing your knowledge. Dean
Being pink 18650 makes me think(99.9%) they are Samsung Li-ion...Being 13s8p makes me think this is 15ah li-ion battery...Also most all Li-ion are 13 series...Do not use lifepo4 charger with li-ion or vise versa...13s x 4.2v(li-ion)=54.6v or a 48 volt bank!
test 1 row of parallel to see voltage when charged up...should be 4 or 4.1
Lifepo4 dont go above 3.7 volts!!!
13s x 3.6v(LiFePo4)=46.8v ,,,,,,Definitely your lifepo4 label is wrong
I have several LiFePo4 batteries...They are all 22650, and they are all 16 series..10 ah,20ah and 40ah...My lifepo4 chargers charge at 60v/6a
Because 16s x3.6v=57.8 volts...a tad heavier, but charge cycles and steady discharge make up for weight...Take care...
Hello,
I have been using 24DC 50Ah batteries for almost two years but I’m concerning about actual real maximum battery capacity. These batteries are working continuously in AGVs, 24h/day, 360days/year...
Which is the best way to measure the real maximum capacity? I was thinking about first full charging and then measure discharge current and time. ... Is there any kind of standard DIY design for battery discharging?
Regards,
Edu
yes .. the best way to know what they really are .. is to test them.
Yes, at the very least full charge for the full discharge test.
I will also say only the rates you will really use them at are the most 'real'.
I also would recommend testing for worst case / hardest .. that way you know that is the minimum they have , and under gentler conditions they will do better.
For example :
If you know you'll drawl a discharge on them at say ~200Amps .. the most 'real' test is one that reproduces that ~200Amp discharge rate .. if you know you'll only go down to __Voltage or up to __ voltage in application .. than don't go bellow or above that in your test either.
Label:
Just because they were sold as '50Ah' doesn't mean they actually were 50Ah to start with on day one .. they might have been 49 or 51 .. without test data to go back to .. you just don't know is all.
The best comparison is when you compare the results when they are tested the same way .. comparing 50a test to 200a test is a bit of an apples to oranges.
------
Most DIY battery discharge testing often uses things like a known resistance heating element as the discharge load .. take regular rate readings with meter of Amp rate and voltage.
But a better test is one that holds that same known rate for the entire test .. soo if you know you're real world load will be say 500Watts , than discharge at a steady constant ~500Watta .. the resistance type will vary the rate as the conditions change .. so, although it can work and is cheaper and easier for DIY .. it is not as ideal / quality of data compared to a more complicated and expensive design that more precisely regulates to the same rate for the entire test.
From mechanical engineering background and worked on IC ENGINE for 15 years I recently developed lot of interest in EV and battery would u please share some vedio for beginners as well
This is the beginner "101" video for LiFePO4 .. Among the other videos I've done 2 that would be good for battery beginners ..
One on NiMH nomenclature.
th-cam.com/video/zxAtrnfHCtE/w-d-xo.html
Also one on the variables that effect battery life cycles / years.
th-cam.com/video/DoyrKXvXSBM/w-d-xo.html
@@ianpgeorge great sir thanks
53:30 He starts listing different chemicals and goes into greater detail about electrochemically effective dimensions
Wish he did what he promised . A 101 on supercapacitors!
I don't see evidence to support your claim .. Where did he make that promise for a 101 on supercapacitors ? .. That claim was not made in this video , as far as I can see. At 9s in he said he "can talk about super capacitors at the same time" .. he did just that , what he said he would do .. several times throughout the discussion on LiFePO4 he did talk about some of the super capacitor aspects at the same time while he was discussing this topic on LiFePO4 .. also .. keep in mind this was a class that went over an entire academic semester .. this is just a short 1hr15m clip from that much longer period of academic time .. and .. at 39.00 he points out the 'come back another time to talk about those' to discuss super capacitors in more detail .. because this was only a short piece of an entire academic year long scholastic activity.
12Watt Solar Street Light on 72Wp Solar PV panel would be powered by 30AH, 12.8V LiFePO4 battery. What other things to be taken into consideration or verified before concluding on requirement?
#1> You need to know the reasonable yield rate from that 72W solar panel .. a solar site survey of conditions / orientation .. that will give you reasonable expected output .. this output will vary as the conditions / orientation varies (such as time of day , time of year , etc) .. this will tell you about how fast the battery is refilled.
#2> You need to know the daily use rate (avg , min, max) of the 12w solar light .. 1hour , 24 hours , etc .. this will give you a reasonable estimate of how much you are consuming per day .. this will tell you how fast the battery is emptied.
#3> You'll need a BMS of some type to make sure the LiFePO4 cells stay balanced .. you can be a human BMS if you want to do it manually yourself .. or buy a device to automate it for you.
#4> You'll need a solar charge controller .. MPPT will yield more wh than PWM .. that fits electrically with both .. the panel output , and the battery design.
#5> You'll need a low voltage cut off .. that fits electrically with both .. the output light load , and the battery design.
#6> You'll need a properly sized fuse.
#7> You'll need a proper container for all of this .. that fits the application conditions .. size, temperature , water , etc.
0:20 hey thats me!
is there a lecture on super caps too???
Sorry, I don't know of one of equal quality as this video from JayW .. The one's I've seen specifically on Super Capacitors are usually far more basic / rudimentary.
what about shelf life? if a lifepo4 is not used. how long is it good for. and what happens .
Everything eventually degrades. The rate of degradation for LiFePO4 (and most batteries) will vary with the details of it's conditions and usage. If not used, that removes many of the variable usage condition variables. You would be left with SoC level, temperature , and quality of the stored cell itself.. Specifically for LiFePO4 , worst case conditions like storing at top SoC, in high temperatures 40+ Celsius, from low quality cells.. you might see degradation rates as high as around ~10% or so per year .. best case conditions low SoC (not zero) , low temperatures , high quality cells .. than you might see degradation rates less than 1% per year .. as for 'what happens' .. the short version, is that you loose usable energy storage and usable power rates (for charge and discharge) .. a cell initially giving ~60wh would then give less .. ~54wh if as high as 10% .. or about ~59.4wh is as low as 1% .. The cell that initially gave you 3,000w , might now only give you .. ~2,700w @ 10% .. or ~2,970w @ 1% .. So far in my own HEV usage, I'm seeing between 1% to 2% loss per year so far , but that isn't just being stored on a shelf, it is being used almost everyday, year round.
Great lecture, very interesting.
I'm interested in the cold temperature characteristics of my Fusion LifePo4 12v 40amp/hr battery pack.
It's says they have an operating range of about -20'C to 60'C, which this lecture supports.
My concern is that I have read other information saying that it is not ideal to charge these batteries in temperatures below 0'C as this can lead to a coating build up?
It gets to -8'C here so I am concerned that after my 4x4 has started its going to try to charge my LifePo4 Aux battery whilst still below 0'C possibly causing damage?
It isn't a black/white thing .. where there is a clear line of A is good and a tiny distance away B is bad .. it's more like a shades of grey thing where A is better than B but B is better than C .. etc .. along a progression from 'good' to 'bad'.
As one moves further and further away from good and more and more toward bad .. shorter and shorter useful/operation life (cycles/years) .. 10 years instead of 20yrs .. or 5 yrs instead of 10yrs .. or 1yr instead of 5 yrs .. etc .. only in extreme cases of cell defect or abuse would it just fail , instead of age/degrade quicker.
That a cell operates at some temperature does not also mean that it is at 100% of it's ideal temperature operation performance.
There is variation even in the general 'LiFePO4' family .. they can be tweaked +this -that etc .. I don't have exact details on the specific battery you have .. That having been said, I can give you some basic principles that apply in general .. and I'll give you an example of how that applies to a specific flavor of LiFePO4 I am familiar with .. If desired you can test your specific battery to quantify exactly where it's specific tweak/flavor stands.
In general the battery performs better but ages / degrades faster in hotter conditions .. and the reverse also .. generally the battery will perform worse but age / degrade slower in colder conditions .. the harder you push a cell the faster is ages/degrades .. harder as in .. How wide the SoC/DoD use window .. or how higher power rates (charge or discharge) are used .. or temperature extremes (hot or cold) .. etc .. etc.
When the application usage doesn't change to reflect the conditions , the result is to 'effectively' be pushing the cell harder.
To give an example of this for a specific battery that I know and have extensively tested .. the A123 version of the LiFePO4 20Ah Pouch cell .. short pulses (as described in the video) can be significantly higher, but the bellow I describe is for the more conservative / safer / continuous use rate.
At a temperature of 25Celcius ~60Amp Charge ~200Amp Discharge .. is about as hard on the same cell as ~40Amps Charge ~180Amp Discharge at 15Celcius .. is about as hard on the same cell as ~20Amps Charge ~160Amp Discharge at 10Celcius .. is about as hard on the same cell as ~10Amps Charge ~90Amp Discharge at 0Celcius .. is about as hard on the same cell as ~6Amp Charge ~60Amp Discharge at -10Celcius .. is about as hard on the same cell as ~2Amp Charge ~40Amp Discharge -20Celcius .. This specific flavor (I'm referencing here) of LiFePO4 should not be charged when it bellow -20Celcius temperatures but still roughly equally hard on it to discharge at ~15Amps down to -30Celcius , and should not be discharged below that -30Celcius .. but the cell (if not used) can be slowly taken down to under -100Celcius and then slowly warmed back up and still be fine.
Now if I were to take that cell and try to force it to take a 60Amp charge rate at colder than 25Celcius temperatures .. than that would mean I am pushing that cell much harder at those colder temperatures .. even though it is still the same 60Amp charge rate.
There can be tweaks and adjustments OEMs can make that will make a specific LiFePO4 cell be a little better or worse than those specific numbers for that specific cell that I described .. but the description explains the concept.
Wow, thanks. And thanks for the lecture.
I saw that he referred to discharge under freezing conditions with no problem, however he didnt mention charging under freezing conditions and I've read from other sources that charging in sub-freezing conditions quickly destroys a battery. Can you confirm/deny this?
Maybe I should make a video in more detail .. as this is a common question that comes up on a regular basis.
The short version is = It isn't a black/white thing .. it's a perfomance curve , with multiple variables interacting and contributing.
Aka:
It isn't 100% then 1 degree of temperature different it goes to 0% .. it's a performance curve .. to push a cell equally hard (as far as wear and tear on the cell) .. you would have to actually slow down doing less watts of power (charge or discharge) as it gets colder and colder .. the specific vary of course from battery to battery (even among the flavors of the same type like LiFePO4) .. but if someone properly takes into account that performance curve , you can continue charging well bellow freezing temperatures like zero Celsius .. and (depending on the details) it might not be any harder (as far as degradation) on the cell as higher power rates at higher temperatures are.
Also .. this curve starts considerably before freezing 0C temps :
For example:
Person A ... charges a cell at 10C temps the same as they do at 30C temps .. and never charges bellow 0C temps.
Person B .. Charges his cells all the way down to -20C temps .. but they change the rate / method of charging , following the cells performance curve as the temperature changes .. starting with equally hard as person A at 30C temps.
In that over simplification .. Person A is actually putting wear and tear on this cells faster than Person B .. although Person B's method is a little more complicated.
Some people don't want to think of the slightly more complex (although more accurate) 'curve' .. and instead they try and make it overly and misleadingly simple by just saying the black and white (don't charge bellow freezing temps).
Also .. it isn't just the temperature alone .. DoD also matters .. C-Rate matters .. Mechanical Stresses matter .. method of charging ... etc .. etc.
Is there any program to apply at the end of life in order to recycle?
My personal preference .. when it can no longer be reused in another application , and finally must be recycled .. generally speaking .. I would discharge each cell as low as I can .. cell level might not be reasonably possible for some battery packs of multiple cells , in which case just discharge as low as I can be done safely .. if if it is a pouch style cell I'd cut off the tabs .. then I'd cover the remaining +/- terminal area with something non-conductive like a piece of electrical tape .. bring the whole thing to an Li battery recycler .. or ship to one if none are in your area .. some recyclers also have their own specific instructions.
HELP... My escooter uses a Chinese-made 48v 20ah 60 amp LiFePo4. I'm confused at the charging directions because the escooter manufacturer directions say to always charge it immediately after a ride. Alternately, the charger's instructions say there's no need to keep it fully charged, but when you do charge it all the way up, leave the charger on for an extra 1/2 hour after it stops charging to balance the cells.. but that makes no sense to me. Besides, if I do that, the escooter will totally die electrically until I disconnect the battery from the controller, then it works fine after I reconnect it. That seems like a controller issue. Lastly, I saw a LiFePo4 video that stated the longer a LiFePo sits at full charge or at a depleted charge, the less life you'll get out of it. Any charging advice would be appreciated, because I've been given too much Chinese information. Nothing makes sense (and a replacement battery is $750.!).
Its a matter of choice ... there isn't one thing that has all pros and no cons .. you have to learn the pros and cons .. and pick what satisfies your own specific criteria / desires / etc:
Item #1> Holding a LiFePO4 battery at a higher SoC or SoE or rest terminal voltage .. holding it up there for more hours .. all else being equal .. will increase the rate at which the battery degrades .. it won't be instant .. it wont' be in a week .. or a month .. but if all else is equal .. the battery that stays at a higher SoC, SoE , or Rested Terminal Voltage longer will age / deteriorate faster ... over years of time.
Item#2> An unbalanced battery pack risks putting additional stress .. ie degrading faster .. all else being equal .. the individual cells that reach the top sooner than the other cells in that battery pack ... and also risk additional stress .. degrade faster .. for the cells that reach the bottom sooner than the others in the battery pack .. the faster one hits the top or the bottom the harder the stress .. the larger the imbalance the greater the stress.
Item#3> The narrower the SoC/SoE operating window toward the middle the longer the cycle life .. all else being equal .. soo a cell that is kept 90-10 instead of 80-20 will experience slightly faster degradation from the wider SoC/SoE usage window.
Item#4> A Warm cell .. all else being equal ... performs better .. it can deliver more power .. has lower resistance .. has more usable capacity .. etc ... but it also degrades faster than a colder cell ... soo one has to pick a compromise point .. where it is warm enough to get satisfactory performance .. but still cool enough to not unsatisfactorily increase the degradation rate.
Item#5> The faster / Harder you push a battery .. all else being equal .. the faster it's degradation .. soo .. you again look to find a compromise ... where you get the amount of performance form it to satisfy you ... but don't push it soo hard that is unsatisfactorily accelerates the degradation.
etc...
Now this last part is the hardest ... weed through compromises of all the various pieces.
For example .. a charger that does it's top balancing .. at the top ... wants to do that balancing in order to reduce the effects of a possible imbalance ... but in so doing it automatically gets into that top zone and the cons of doing that ... you probably don't need the balance corrected every single time you charge it .. soo you could choose to shy a bit away from the topping losses .. and a bit more toward the balance losses .. doing less balancing .. but still doing some occasionally ... by not charging all the way to the top .. you are also choosing to voluntarily give up some of your usable range .. if you can do that on both top and bottom , it will also help prolong the usable service life of the battery .. but it will mean you are voluntarily lowering your usable range.
Soo you see there are pros and cons ... but .. if you know how they effect your battery .. and what you personally want /need from your battery ... than you can make the choices that are the best fit for your particular usage ... someone else might not have the same wants/needs as you do .. so they might make different choices for different pros and cons.
There really is not .. one size fit all.
Well Ian, you've given me some great info here for Summer usage and I thank you for it.
So, when I store the battery for the Winter months, I'm thinking I'd balance-charge the battery to 100% and then run it down to about 75% SoC. I'd give it a short charge each month to keep it around 75-80%, unless that's unnecessary??? Also, Do you mind if I post your response(s) on my Escooter Club site on Google Groups?
You're welcome .. happy to help.
I don't mind you copying my posts to other threads or such .. Happy to help.
The reason to keep it up as high as that 75-80% SoC/SoE .. would be because you want it ready at a moments notice to be used .. If instead you know it is going into winter storage .. and you are not likely to use it .. or you will be able to limit yourself to charge it up just before you want to use it .. than it would be better (in the long run , all else being equal) .. if you stored it at a lower SoC/SoE .. down around 40-50% is better than 75-80.
The only need for occasional short storage charges .. would only be needed to counter the amount lost to Self Discharge and any load taken from the batteries by your BMS.
Depending on SoC/SoE and on temperature .. it is reasonable to expect a good quality / good condition LiFePO4 cell to have only as low as 1% to at most 4% Self discharge per year .. higher at higher SoC/SoE , and higher at higher Temperatures .. but still it's very very slow on it's own .. some of the BMS people use , drawl more than this and can drain the battery faster than any low Self Discharge it might have on it's own .. LiFePO4 cells that are self discharging faster than about ~5% per year .. I would begin to keep a closer eye on them .. that's far faster than it should be .. might still be usable / manageable for a long time .. but it would still be an indication that something is less than 100% about the cell if it's self discharge rate is that fast.
Remember a BMS that drawls even as little as ~1mA .. running 24/7 .. will all by itself ... even at that ~1mA will consume about ~8.7Ah per year .. you will either want a physical disconnect for the BMS to prevent it from draining the cells during storage .. or you'll need to do those short storage charges often enough to counter and replace what the BMS took/used.
Actually it sounds like you have a cell(or 2) with a loose weld...once you hit a bump, your bms cuts out because I parallel set jumps too low...once you reconnect you are good till next bump...it could be loose wire somewhere in between, or in BMS or controller...Check all connections before battery breakdown.I've done a Battery teardown time or 2...R U positive they are LiFePo4???? Are they stock from factory???
NEVER charge battery below 5 celcius! Store a battery for winter at 80% capacity!
Full charge is fine, but not all winter!Also dont leave depleted all winter!!!
GOOD
Ian, i'm the guy that you helped with the escooter Lifepos last year, not sure if you remember? Anyway, I have a idea for people who ride ebikes and escooters with typical LiPo batteries who suffer, like I do, from range anxiety.
Is there a way to make a super small, no cord, 52v super capacitor battery booster that one could just remove the battery from the ebike or scooter and plug this booster directly into the XLR charge port (not USB)? This would be to just give the rider a few extra bars on their meter to help get them home. Just wondering if you think this is doable. PLMK if possible.
I have no doubt that would be 'doable' .. however .. That isn't the direction I would personally advise/suggest to someone.
1st
I would suggest having a battery range installed that properly fits the application.
2nd
Present super capacitors hold much less energy per unit weight than present Li battery options.
Even if someone wanted to carry the dead weight around that most of the time they never use .. they would have more joules/calories/wh/etc of usable boost range distance by doing so via a Li Battery (not a super capacitor) .. or they could carry the same extra miles as the super capacitor but it would weigh less.
3rd
If someone wanted a hidden/emergency reserve .. it would be smaller space .. lighter weight .. etc .. to just do that in control software , while using the larger (better fit to application) single battery (like 1st above).
--
That's just my 3 bits (personal preference).
@@ianpgeorge Well, I guess I should say that this "booster device", in order to be marketable, would have to fit certain criteria and in some aspects may possibly be more form over function in order to be sellable. Having it built into the control software would be nice, but since it's for any ebike or escooter, that would be tough. It would be sold as emergency power to either get you home from a miscalculation of range or give piece of mind to those who often push their battery range or have older batteries with declining range. Again... It's insurance for people with range anxiety. It MUST be super small and light weight, no a/c or charging cords unless self contained, simple to use. Maybe it will have a dynamo hand crank that charges some super caps. Maybe pedaling charges it??? Idunno. What do you think. PS. I have a micro hand crank dynamo I ordered from China. It's sort of junkie and would take a lot of cranking just to partially charge even a phone, but if it were made well, could it charge caps enough to give you a few miles?
Could such a device me made ?
yes , absolutely no doubt at all.
What do I personally think about it ?
There are smaller, lighter, cheaper, more efficient, etc.. ways to achieve the same effect.
@@ianpgeorge What would this smaller, lighter, cheaper, more efficient thing be precisely? Sorry, I don't mean to push.
There isn't just one (precise) way .. there are numerous ways .. each have their pros and cons .. but the cause is just the choices you're making in your design (as described thus far).
You might have any number of perfectly valid reasons (whatever they are) for why you've made the choices you've made .. but whatever your reasons are .. whatever the other (non-functional) benefits they offer .. marketing / press / whatever .. they still have consequences , such as increases to cost , size , and weight.
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Hit #1> Super-Capacitors
They have their pros and cons .. the application you've described doesn't benefit significantly from any of their benefits .. (fast charge , fast discharge , high cycle life, etc) .. at the same time the proposed application is harmed significantly by their cons .. (more expensive , more volume for the same energy , more weight for the same energy, etc).
Just by you wanting to specifically use super-capacitors instead of any of the various other options .. you are automatically more expensive, bigger, and heavier than any of those other options that have would have less volume for the same energy , or less weight for the same energy , or less cost for the same energy .. if you don't want this increase in cost , size , and weight .. than drop the intent to use super-capacitors .. or just accept the consequences (cons) of the choice to use super-capacitors.
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Hit #2> 2nd battery hardware
You dismissed my previous suggestion to just use a properly sized single larger energy storage (battery,etc) , and implement this same feature in the eBike's software .. well .. that choice forces you to be more expensive , larger , and heavier .. when compared to someone who instead did implement the same function in one larger/better fit to application energy storage device (battery) , and used software.
again .. if your want to avoid this price , size, weight increase .. than drop the intent to use a 2nd separate hardware energy storage .. or .. just accept the consequences (cons) of the choice to use a 2nd separate energy storage hardware.
What's your thought about the headway 38120hp used in a "high discharge setup"
My thoughts .. #1> 'high' is vague , I'm not clear on what specific amount you are thinking of , under what specific conditions .. #2> OEMs published specs are usually either a little on the optimistic side .. or cherry picked under ideal conditions .. or a combination of both .. #3> It isn't a black and white thing .. the harder they are pushed the faster they degrade .. That will include a combination of Charge Rate , Discharge rare, Temperature (high or low), CoC/DoD usage window , etc .. etc .. #4> Although 3 above (faster degradation) is very often the result .. Cell outright Failure is possible , and the harder you push a cell the higher the chance of cell outright failure .. so, if you intend to push it hard it becomes more important that you engineer into your application contingencies to safely mitigate such outright failure.
Ian George
So over build is definitely the way to design a high output battery pack.
Edit.
How much would 96ah handle?
It will depend on the specific cell .. and the context (temperature, thermal management , duration, etc) .. not all cells are equal .. the best way to be certain is to do a test .. testing it under conditions that are harder/worse than the real world's worse case.
I've seen some that are perfectly ok with sustained full cycle over 5C rates.
such @ 96Ah x 5C = 475Amps
I've seen some that are perfectly ok with bursts of a few seconds up to 20C rates.
such @ 96Ah x 20C = 1920Amps
But in the very cold (bellow freezing) all those rates drop down allot.
The same cell that does ~20C bursts for a few seconds when warm (but not hot) .. might struggle to do more than 2C burst for a few seconds when it is down near ~0F .. some cells are designed/tweaked specifically to do a little better in the very cold, or very hot.
And of course if you are ok with shorter useful life time .. like hundreds of cycles instead of many thousands of cycles .. well then you can beat on them a good bit harder.
Ok,
Say I have (4) 3.3v cell's in series with a "maximum discharge" of 240amps each.
Would in series be 240 amps total or 960?
Ian George
What high amperage cells would you recommend
What is duty cycle LFP battery?
The phrase 'duty cycle' .. for any battery (not just LFP) .. is the range of the battery that is used during application cycles of charging and discharging .. this is not a fixed thing .. there are pros and cons of different options that the system designer picks the trade off they are satisfied with .. for example a battery that has a duty cycle from 25% to 75% , has the pro of it would last a long number of such cycles/years .. but the con of not using 50% of the batteries maximum ability .. you had to pay for that battery in $ and in space and in weight , even if you don't use 50% of it .. if the same battery had a duty cycle of 1% to 99% , the con is that would not last as many cycles as the 25-75 , but the pro of using 98% of the batteries maximum ability.
What is going on with my battery pack? The label say LiFePO4, 54.6V, 576 Wh. It is 8p 13s, or 4.2V per 8p row. So it must be LiPo, not LiFe, right? The label on the charger that came with the battery says 48V2A Lipo. Why would they mislabel the battery, or is there some new chemistry that lets LiFePO4 charge to 4.2V per cell? Thanks, useful video.
I don't know the battery .. nor the company .. so I can't speak to why it's labeled some way , or why they did something.
I can say the following though:
#1> LiFePO4 charge to 4.2v per cell
Technically any LiFePO4 cell could be charged to 4.2V per cell .. but it is exponentially more likely to result in cell failure .. and at the very least it will result in cell degradation / shorted service life (cycles/years).
This is part of the end of charge .. when the terminal voltage goes exponential at the very end .. and the harm to the cell .. and the risk it causes is why most people never push a LiFePO4 cell any where near that hard (high of a terminal voltage).
#2> Integrity of Label:
If you doubt the integrity of the label .. than that in itself also puts doubt on anything the label say .. be it the LiFePO4 part .. or the 54.6v part .. etc.
You could always check it directly .. calculate the nominal voltage under some known discharge load rate .. watch for the low end terminal volt rapid drop off point .. watch for the top end terminal voltage rapid exponential increase point .. etc ... once you have your own validated test data , you will be better able to confirm / refute/ etc whatever is on the label.
If you directly verify for yourself that it is say 8p13s .. and you verify the voltage profile .. you can get a fairly good degree of certainty that way.
It is also worth noting that mistakes do happen .. A company that makes multiple different kind of battery packs .. might have just accidentally put the wrong label on a battery pack.
#3> Battery Labeled by intended market:
It is not uncommon for battery companies to label a battery to a specific battery market .. ie .. labeling a battery as 12v .. doesn't mean you actually see 12v measured at the battery terminals .. it might only mean it is intended for a 12v battery market.
Automotive 12v battery is a easy example .. the actual battery voltage varies considerably depending on SoC/SoE .. Temperature .. Load .. etc ... so even though it might not actually give you 12v .. it might still be labeled as a 12v battery ... meaning it is intended to be used in 12v battery market.
Actual battery voltage varies widely depending on conditions .. SoC/SoE .. Temperature .. Rate of charge .. Rate of Discharge .. etc .etc.
#4> LiFePO4 not specifically listed on the Charger:
Like other members of the Li family ... LiFePO4 top end of charge safety termination can included watching the terminal voltage for the tell tale exponential voltage increase ... a charger smart enough to identify that shape .. Any Charger smart enough to do that can charge any Li Battery .. ideally with cell level monitoring or BMS .. but the end curve is the same shape for any of the Li family of batteries.
However ... if the charger isn't smart enough to identify the end of charge terminal voltage shape .. and instead it just always goes to a specific CV set point .. say ~54.6v for example .. that isn't as (universally) safe for all members of the Li family .. because it could be way high for some batteries .. for example no 3s Li family battery should be taken to 54.6v ... but say 15s LiFePO4 pack would not be unusual to see a top end CV phase of 54.6v ... but 13s , would be really pushing the cells very hard (if they were LiFePO4) etc.
I hope that helps some ... best of luck.
read above
Being pink 18650 makes me think(99.9%) they are Samsung Li-ion...Being 13s8p makes me think this is 15ah li-ion battery...Also most all Li-ion are 13 series...Do not use lifepo4 charger with li-ion or vise versa...13s x 4.2v(li-ion)=54.6v or a 48 volt bank! test 1 row of parallel to see voltage when charged up...should be 4 or 4.1 Lifepo4 dont go above 3.7 volts!!! 13s x 3.6v(LiFePo4)=46.8v ,,,,,,Definitely your lifepo4 label is wrong I have several LiFePo4 batteries...They are all 22650, and they are all 16 series..10 ah,20ah and 40ah...My lifepo4 chargers charge at 60v/6a Because 16s x3.6v=57.8 volts...a tad heavier, but charge cycles and steady discharge make up for weight...Take care...
Thanks a lot sir! U Cleared many doubts of mine. Could you discuss a little more on d equivalent circuit design of d battery & explain d various resistances and d capacitor? Y r we still using LiCoPO4 in mobile phones instead of LiFePO4? Could u take a similar class for EIS studies of a li ion battery? Kindly provide ur maid id so that v can easily contact you sir. Thank you.
I am not the professor in the video .. I uploaded his video to my youtube channel for the benefit of others .. I am not clear on what your are asking about with regard to equivalent circuit, please clarify/describe more what specifically you are asking about ... As for your other question , why the industry doesn't currently use LiFePO4 flavors often in cell phones (and similar).. Batteries can be tweaked and modified extensively to better fit the specific needs of a specific application .. There is no 'one size fits all' , version of battery chemistry that would be the 'best' in every possible application .. While LiFePO4 could be used in cell phones, the industry uses other 'flavors' instead intentionally .. LiFePO4 is a 'safer' chemistry, but others already used for cell phones are 'safe enough', soo being safer than 'safe enough' has little additional benefit .. LiFePO4 can safely handle much higher rates of charge and discharge, but others already used in cell phones are able to keep up with the power needs of the phone (that application) , so unless a cell phone also has a built in tazzer or car jump starter feature there is little benefit for the additional power rates that other types like some of the LiFePO4 flavors could do .. For example the type of LiFePO4 battery I used in my PHEV conversion can safely handle bursts of charge or discharge up to 21C rates , that is almost 10x times faster than what Tesla BEVs can do, or what cell phones and lap tops can do .. but those Tesla BEVs, cell phones, and laptops instead have about 2x the stored energy .. it's a trade off .. Sense those other applications more benefit from wh/kg instead of w/kg they choose to tweak and use the Li flavor better suited to the specific application.
Oh I got it! Thank you ! Actually regarding my first question, I could not get d various electrical components u added to d electrical circuit , that is d ''resister'', d ''capacitor'', and d ''warbour resistance''. I wish to know d exact significance of each of d electrical component.
What do you mean by your use of the single letter "d" in your last comment ??
You put this single letter "d" in front of various different things in your last comment .. but "d" by itself isn't a word .. It might be a variable or reference to something else .. but right now I don't know how/what you are using that letter "d" for.
Sir, actually I use "d" for "the". Sorry for that.
That's too broad .. please narrow down your question to something more specific.
The 'exact significance' of each of those will depend on what you are referring to .. and in what application / context you are referring to.
Also keep in mind this video is not intended to be 'exact' it is a basic overview .. like if someone was describing the basic overview of a car .. in general as a concept .. which is very different from 'exact' or 'specific' description of one specific car.
For example:
The resistance of external electrical load sink .. is not the same concept or significance as .. the resistance of a BMS's various resistors .. is not the same as .. the resistance of the power electronics .. is not the same as .. the effective resistance the battery itself has .. etc .. etc .. Same goes for capacitance, inductance, etc.. etc.
Even if we narrow that down to just the 'effective electrical resistance' of a specific battery itself .. the 'exact' or 'specifics' , or 'significance' .. of that 'effective resistance' will change .. with different applications .. different usage situations .. different cell temperatures .. different SoE/SoC .. different rate of charge/discharge .. etc .. etc.
There seems to be a mix of dangers from colbalt vs lithium iron PO4
very nice lecture and explanation, however I do not know why he was explaining so fast
so... lithium cobalt is a cell phone battery, lipoly is fragile and catches fire easily if over/under charged, and lifepo4 is relatively safer than lipoly right? what is a general chemical makeup of lipoly, and what makes lipoly so dangerous at charge extremes?
I'm guessing it has to do with cell voltages being closer to electrolyte breakdown voltage but that doesn't explain the problems with over discharge.
I'm not sure how in depth you want to get .. one can only say kind of general things with only general levels .. not all LiFePO4 are the same , anymore than all Lipoly are the same ... etc ... Generically .. Yes , the electrolyte break down is part , but so are the Anode and Cathodes loosing effective active material , and surface area as well ... The over discharge and high rates , are issues of unwanted chemical reactions .. Those unwanted chemical reactions can be dangerous .. or just shorten the total cell useful service life .. it can be in the electrolyte ... but it can also be in other parts of the cell.
What I cannot create, I do not understand. -richard feynman
I'm originally coming at this from an rc hobby perspective and specifically I was looking at batteries from hobbyking.com. Once lipoly batteries are drained hobbyists treat them like bombs keeping them in special bags and charging $50+ for cheap Chinese chargers. Then I heard of lifepo4 batteries that are supposed to be safer. So I just considered buying those types of batteries. That's what has brought me here to this video. You have taught me a lot, thanks.
I'm assuming some of this carries back to lipoly cells, but I'm having trouble finding the possibilities of what the electrodes could be made of to get even the foggiest of reasons why running a cell down to 1 or 2 volts can cause an issue.
In your video you only mention catastrophic failures with lifepo4 with negative voltages on the battery(electrolyte breakdown and venting), but I think you only warn of lifespan issues with low voltage.
Can you point me in a general direction of what lipoly could be made of and what kind of reactions could cause failure with over discharging?
At it's most generic .. The behavior you are asking about is a .. 'better safe than sorry' .. based behavior .. which is perfectly understandable and reasonable .. in a general/generic sense .. The cell chemistry is stable and functional within a certain range not higher than X not lower than Y .. SoC/SoE/Voltage/Temperature/etc .. There isn't a black and white line in the sand ... It's more like a shades of grey .. The further you go toward the ends of that 'safe' range .. or the further past it .. more of those unwanted chemical reactions are more like to happen and happen faster .. There have been cells that have been over discharged and still functioned fine .. but that becomes less and less likely the further they were pushed beyond the 'safe' range .. Most of the time when the cell is not taken far outside the 'safe' range .. the unwanted reactions just reduce useful cell life .. But there have also been batteries that caught fire , released toxic gases , etc .. Again it's shades of grey .. not a clean line at one single point. ... Lipoly is a generic term .. Battery companies can and do make them a number of different ways with thousands of different chemical combinations .. The name itself only tells you 2 basic / generic things .. #1> It's a Lithium reaction based battery ... #2> It uses a Polymer .. that's it .. that polymer could be a polymer electrolyte , just a polymer cell case ... etc .. the name alone doesn't tell you allot of details ..You can get some more detailed information about a specific battery by getting the 'Safety Data Sheet' for that battery .. Although they usually still won't easily disclose everything they use or put in that battery .. after all they don't want others copying them after they spent millions on researching and producing that specific chemical recipe .. Yes certain 'families' like LiFePO4 are 'safer' than other 'familes' .. but even than there are still thousands of possible variations among different battery companies .. Now generally speaking it takes energy to do any 'work' .. soo the unwanted chemical reaction from a battery with more potential energy .. high charge , high temperature, etc .. that higher potential energy content means that cell is more capable to do more 'work' .. good or bad work .. than a lower charge / temperature cell could .. but even 'flat' and 'cold' there is still potential energy content there.
It's all about the specific chemistries and constructions. The subject you want to research is "thermal runaway". When you short a battery (on purpose, by accident, or by misuse), there will be an enormous current flow. Because all batteries have some internal resistance, that means there will be heat generated. A lot of heat. Very quickly. Various LiPo chemistries have differing levels of tolerance to high temps. First gen LiCo is very well known for it's rapid, unstable runaway leading to "explosions" (albeit on the scale of a firecracker) and "venting with flame" :-) Second gen LiCo (NCA - NiCoAl) is slightly less prone to popping, but only marginally. (they're still firecrackers. This is the technology Tesla uses.) [3rd gen NMC is _much_ better] LiFePo has next to no thermal runaway issues. They can generate tremendous currents without damage. (which makes them popular with DIY EV car conversions.)
Over-discharging leads to irreversible physical and chemical damage. This greatly reduces the cycle life of the battery, but does not cause them to "vent with flame". Rarely will this instantly destroy a battery -- so long as it's not "zero volts", recharged soon (or immediately), and you aren't making a habit of it. Manufacturers run tests and provide datasheets showing the charge/discharge lifecycle of their cells.
jfbeam thanks for explaining that. off the top of my head I was looking for something like how these chemicals are arranged in the anode/cathode/electrolyte/ or separator and what exothermic reaction is causing the problem
Hey can you publish a link to your white paper regarding the charging.
I do not (myself) have a 'white paper' on anything.
I might be able to provide more assistance, if you can give me some more details about what 'white paper' you are looking for .. or , if not a specific 'white paper' , what specific topic you are looking for a 'white paper' on.
Sorry .. a battery .. even LiFePO4 ones .. being charged .. is still very broad / general .. there are lots of aspects / parts of that.
@@ianpgeorge hi I am looking at charging technics of Battery Banks. I am playing around with charge circuit. I want to look into series configuration. I think Battery Management is very well understood but I believe there are a few hidden trade secrets. I am looking at LiFePO4 and Li-Ion chemistry.
Yes .. Battery Management itself is very well understood .. the exact hardware and software a given OEM uses to achieve that is often the 'trade secret' part .. for instance it is common to reduce charge rates into Li based batteries as they get colder and colder .. the exact electrical schematic and programmed algorithm that Tesla uses is a Trade Secret .. but it is well known to do such things.
You need fairly well matched cells in the pack .. capacity, power , resistance , self discharge, etc.
You need some passive fail safe measures .. fuse , vent , case, etc.
You need some active protection (slow/stop @ top/bottom) , detect cell/battery fault, thermal management, etc.
It is not uncommon for an OEM to 'tweak' battery chemistries for a specific application .. gaining item 'A' at the expense of reducing item 'B' .. which means , not all batteries even in the same group .. such as LiFePO4 , will have identical properties .. two differently tweaked LiFePO4 cells will be a little different from each other .. the power rates can be different, energy density can be different , self discharge can be different , etc .. the exact method of how they accomplish those 'tweaks' is often what are 'trade secrets'.
Without knowing for certain the characteristics of a specific cell .. you can either just use 'generic' / 'general' criteria for that type .. it won't be as well matched to it .. compared to if you know that specific cells specific details .. sometimes the OEM publishes the performance / usage / application details .. other times you have to look for (or do) testing data in order to experimentally determine any 'tweaking' that might have been done to a specific given cell.
For example I read through lots of published data on a few different 'tweaked' version of LiFePO4 before I picked a few to do another ~2 years of my own testing in order to gather more data on those specific 'finalist' cells .. before I finally picked the one specific 'tweaked' version I would use .. and then designed and fabricated the battery system for the car .. There are some parallels , but not all LiFePO4 are the 'tweaked' exactly the same... neither are 'Li-ion' , etc.
@@ianpgeorge thanks. What r&d are you doing now?
@@ianpgeorge I can see the trade secrets being issue with the batteries. There is a interruption of the cell characteristics.
Hey nice sir....@
He looks like David Wallace 😁
can someone 4K upscale this plox?
Does anyone know why you should not charge LiFePo4 batteries when below 0 degrees C? Apparently this permanently destroys them.
That (bellow 0C) is a commonly quoted thing .. but the chemistry doesn't actually work that way .. the (bellow 0C) thing is at best an over-simplification .. at worst just spreading incorrect information .. it isn't that simple or that black / white of a thing .. I touch on that topic in another video of mine .. perhaps you should start there.
th-cam.com/video/DoyrKXvXSBM/w-d-xo.html
@@ianpgeorge Excellent thank you. I have seen datasheets that list -5C as the minimum charge temp. People will say things like don't charge "below freezing" but that correlation seems odd since no water is in the cell. I have also heard that you can charge safely if done at a reduced rate. Will check that video now, thank you!
@@thedillestpickle The speed of the Li ions slows down with colder temperatures, therefore the charge rate must go lower, too. Bad things happens if you try to recharge too quickly, when cold. Exactly how fast is too fast when too cold ??? So, they just say don't do it. But it can be done, just at a SLOWER recharge rate ...
01:09:57
😀👍
I have a comment re LiPO4 over discharge. A 26.2 v 20 ah i had custom built for a project
Evidentiary had a BMS that was defective or drew unreasonable parasitic current.
During 7 months of storage the battery was ruined, not a single good cell. I tore a few open, and the dissolved replated copper from anode current collectors was obvious as a coppery sheen on the anode active material. Cell voltages were from 0 to 1 volt. $500 Down the drain. So beware of copper plating During over discharge.
I later bought 16 LiPO4 cells to resurrect the project. I was Shocked that these new cells arrived with 0.8 to 0.95 volts.
I thought they sold me garbage but i charged and discharged them and All were came up to stated capacity.
So I'm confused.
Can anyone tell me why the new ones were perfectly good and not copper plated?
To your post .. I would have a 5 part response:
1> All the bellow being said .. I would recommend you avoid going bellow 3.0v discharge on LiFePO4 cells .. to any significant degree on any regular rate .. there are significantly diminishing positive effects the further you go bellow that .. and at the same time significantly increasing risks of negative effects the further you go bellow that .. I am well aware there are many people who go well bellow that , they differ from me in their subjective opinion of where the pros outweigh the cons.
#2> I suspect you are conflating correlation with causation :
For example of concept .. If someone hears a rooster crow before the sun rises everyday .. they notice a correlation .. but the rooster crowing is not the cause of the sun rising.
Noticing a correlation .. __ Substance inside a bad cell .. that doesn't necessarily mean that what you noticed happens to be the cause .. nor does it prove your theory of the copper dissolving and re-plating .. just because the new cells (you didn't open and test) worked, doesn't mean they didn't have that substance you noticed in the bad cell .. at present assuming it isn't there is just an un-tested theory.
#3> I don't ( off hand) see a mechanism for your theory to have happened.
"dissolved replated copper" .. as described in this video .. copper foil on the anode has graphite attached to it .. it is the graphite that is physically between the anode copper and the electrolyte .. Graphite does not dissolve copper foil (no mater what your BMS did) .. if the copper foil ever somehow got 'dissolved' (as you wrote) that would be electrically like cutting off the anode from any external device , no longer a electrical path to the world outside of that cell .. that would have prevented your BMS or any device (external to the cell) from drawing any current from the cell (ie would be permanently 0V) .. even if that were to somehow happen .. it only leaves another problem .. what changed in the chemistry inside this sealed cell to then extract that dissolved copper in order to do that 'replating' ... sooo ... I don't see a mechanism by which your theory of what happened .. could have been what actually happened inside the cell.
Without more data to show otherwise .. I suspect you might have seen the copper foil of the anode .. not dissolved ,and replated .. just the anode is copper foil coated with a layer of graphite.
#4> Potential difference in how it effects a cell to be 'driven' to a given voltage.
When a new cell is made there is a (for lack of better term off hand) a 'evenness' , to the composition .. when you 'drive' a current (charge or discharge) .. you are seeing a 'macro' level net of numerous billions of molecular level interactions .. what this means .. is that if you 'drive' a cell to say 1v .. that 1v is the 'macro' combination of all those .. it is the net of all the tiny molecular level 0.9 , 0.8 , 1.1 , etc ... if a cell were 1st made with that same 1v , the deviation or internal 'spread' from that 1v is smaller , than if one got to that same 1v via charge or discharge.
#5> There are significant benefits to initial 'formation' cycling.
As described in this video .. as such .. if you get a 'new' cell that is (at rest) under 2.6v .. it is highly likely that whoever made the cell .. did not do that initial 'formation' cycling .. even if the cell works fine .. it would have worked better longer , if it had been correctly initial formation cycled.
@@ianpgeorge
I was just asking a question and I thank you for your answers. But copper anode current collector dissolution during overdischarge is a well known problem in li ion cells.
I respectfully suggest you do a little search on this topic sir.
@@davidpacholok8935Likewise .. I was just trying to answer/respond to your request of me.
In this 2nd comment you reference Li Ion chemistry .. previously you were referencing LiFePO4 chemistry .. Please stay on the topic being discussed .. switching between different battery chemistries mid-conversation is not usually very helpful to achieve a productive dialogue .. apples to oranges and such .. yes there are some similarities (both fruit , both plants, etc) .. but generally speaking .. if you want to have a dialogue about LiFeO4 .. staying on the topic of LiFePO4 is usually helpful.
You proposed a theory .. you provided no proof to support your theory .. I pointed out some of the potential issues I saw with your theory .. If you have evidence to site to back up your theory .. please , present that evidence .. if not ..oh well .. you just have a unsubstantiated theory.
As far as I am concerned .. It is the burden of the person making the claim to provide the evidence to support their claim .. no one is by default automatically correct in anything they might claim .. the more extraordinary the claim made , the more extraordinary the burden of evidence on the one making that claim.
Falsification .. finding the issues with a given theory .. is the bedrock foundation of all science .. IF you have a theory/claim ... science says you welcome and seek out the falsification of it .. yes men around you who only agree with you are not helping you .. if someone else finds a fault with your pet theory , that is a good thing.
I am not perfect , nor omniscient , nor do I claim to be anything of the sort .. When someone comes to me (as you did here) asking me for my opinion .. I try to respond appropriately .. If something new is learned in the dialogue (by you , by me , or by anyone else reading it) .. great .. if not oh well .. I'm not perfect , I made an honest effort .. that's all anyone can do.
There are some problems with coherence.
wow so there's graphite in the batteries I guess it's like Chernobyl if you suspect something happened to your batteries while you were away and you find graphite on the ground you know something bad happened.
Please bring a camera next time instead of a potato
Didn't this guys salt water battery company go BK
This video has no subtitles. Can you upload its subtitles?
No , I can not .. such is beyond my current video editing skills.
@@ianpgeorge It's OK . thank you very much. maybe I'll ask my friend to translate this video for me.
I have not watched all of it, but isnt the elephant in the room that discharge charts have no bearing on EV reality?
They assume a motorist uses a constant rate of power.
Rot of course. Its hugely variable.
Which begs the question, "How is the chemical reaction affected by varied use?"
Clearly any heat issues would be far less for short bursts than for constant high C rates. Intervals of low c-rates may yield a buffer of extra discharge capacity for bursts of high C-rate use?
Surely more real world discharge simulations are called for to better evaluate suitability to task?
That is not the elephant in the room .. Your base assumption is that the varying load test is not done .. that is not a necessarily correct assumption .. Sure some individuals don't do rigorous / detailed testing like that .. but some (like me) do .. You are correct it can give more information / validation on how a given battery will behave under those conditions in the real world .. Which is part of the reason why I did it .. For example I did numerous variations in my own testing ... I varied charges and I varied Discharges ... some were constant current , some constant power , some constant voltage , some set energy pulses .. some were not constant anything, and varied over a programmed test sequence , some at various different levels of SoC / SoE charging , some at various different levels of SoC / SoE discharging ... etc ... etc ... by me doing the additional testing I have more data .. thus I already have a better evaluation than someone who would only do a more limited / simpler type of test or tests.
More like EV reality(Tesla) needs to catch up to smaller, lighter, urban vehicles like the whole world is introducing right now, that love these low speed, high charge rate, safety, dependability and green factor...Much cheaper than Lico will ever get, and better to recycle...There are also many better Powerwalls now that use this technology, going away from high density LiCo...
Too much monitoring with LiFePO4. I'll stick with simpler and cheaper AGM.
It's your life , do whatever you like .. but .. just so you know :
#1> AGM is almost always , only cheaper on short time scales .. in the long run (10-20 yrs +) AGM is almost always ends up being far more expensive than similar performing LiFePO4 options.
#2> For most applications/people .. automated battery monitoring / management is proffered .. Even those who use AGM often use automated systems .. prevent over charging , prevent over discharging , etc .. thus it ends up making no difference to the user if it's AGM with automated systems , or LiFePO4 with automated systems .. either way .. the automated systems (once configured) do their job.
Ian George... what are you talking about? Smart chargers charge AGMs near perfectly with no monitoring. It is a set it and forget it type deal. Used AGMs can probably "hang" with or beat LiFePO4s over your 10 to 20 year period. I might need 2 or 3 sets of used AGMs during that period but if they cost 1/4 of the cost of your 10-20 year batteries (I assume new), then your statement will be wrong. Would you like to compare real world prices of good used AGMs vs 10 to 20 year LiFePO4s? I am up for the challenge. I have an advantage because my old AGM batteries have scrap value so a 100 pound AGM has a value of $20 so if it cost me say $75 originally, the real cost (to use it all of those years) is only really $55. This is just an example, not the real prices.
Also, in your #1 point, that assume that the user of the LiFePO4 batteries knows what they are doing. If they make a big mistake, they could easily damage them. For example, if someone cuts corners and doesn't balance them often.
Your #2 point is not very accurate either. Almost all inverters I have seen (which are frequently used to discharge batteries), have built in low voltage protection. Generally under load, the inverter will NOT let the batteries drop below 10.5V per 12V of nominal voltage. How the hell then are you going to over-discharge the batteries then??
You made allot of different claims .. soo .. my response will be a little lengthy in order to cover what you wrote.
I will put "---" as a means to try and identify sections addressing the same concept.
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The smart charger is the same to effect to both .. that is the same as The #2 I previously listed.
You describe using a smart charger to automate the monitoring of the AGM .. someone else uses a smart charger to automated the monitoring of the LiFePO4 .. net result in both cases is the same .. set it and forget it .. the automated system does the monitoring for you .. With actually zero monitoring (nothing stopping over charge, or over dis-charge) the AGM can die pretty quickly .. That is why automated systems (that make it set and forget) are more popular for most battery applications (AGM , LiFePO4, etc)
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Used product comparisons get tricky .. like a used car .. the condition / value / deal .. one person got one time .. gets can vary significantly .. it has much less to actually do with the actual battery chemistry itself .. and more about the 'hand' the person happen to be dealt .. maybe the used AGM (or LifePO4) happen to be a bad deal next to dead (it has happened to people) .. or maybe they are great conditions / a great deal (also has happened to people).
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Your claim about my statement.. "then your statement will be wrong" .. is itself incorrect .. My statement would not be wrong , even in the situation in which you described .. I did not make an absolute statement .. I didn't say it was impossible .. I claimed .. "Almost always" in #1 .. and "Most applications" in #2.
Just like pointing to one lottery winner doesn't change how unlikely that is to happen .. or in this case describing an imaginary hypothetical lottery winner , also does not change how unlikely or likely it actually is to win the lottery in the real world.
After all .. a made up an imaginary hypothetical example .. if that were possible (and I think it is) .. all that shows is that it is hypothetically possible .. it says nothing about the frequency or distribution of it in the population .. and .. I too could just as easily make up a different imaginary hypothetical example with different results .. and it too would also have no effect on the frequency or distribution in the real world population.
One off examples (even if true) don't make a good case for anything .. and luck of the drawl one gets with the condition of used batteries (AGM or LiFePO4) is not really about the battery chemistry itself , it's like buying a used car .. some are lemons some are diamonds (it happens to people sometimes).
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Also don't forget .. battery application performance is not just the cycle life of the battery itself .. your AGMs are less cycle efficient .. and have larger self discharge .. and have lower power density .. and lower energy density .. etc.
For example:
If AGM used in solar / wind /etc .. you have to pay to install more kw of solar/wind just to get the same kwh of energy out of them to use .. and they wear out much faster.
If used in any mobile application .. Scooters, RC , HEVs , BEVs , etc .. AGM seriously reduces usable range , reduces usable power , increases energy per mile cost , wears out faster , etc.
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As for your comment about " knows what they are doing" .. That applies equally to both AGM or LiFePO4 .. the person who doesn't know what they are doing .. is able to kill either one .. or any battery for that matter .. thus .. that too .. has virtually nothing to do with the battery chemistry itself.
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Your claim "Your #2 point is not very accurate either." ... In what way ? .. Please elaborate specifically on what is inaccurate ? .. I don't see any part of your comment describing an actual inaccuracy in the #2 point I made above.
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In response to your question .. "How the hell then are you going to over-discharge the batteries then??"
I'm not sure why you would want to .. but .. if the automated monitoring system you are using is only looking at the whole pack for that low voltage point 12v or 10.5v .. it actually isn't all the hard to over-discharge like you asked to do:
For any battery chemistry (AGM, LiFePO4, etc) .. off the top of my head :
OptionA> If the series cells that make up the battery pack in question are not well matched.OptionB> If the series cells that make up the battery are not well balanced.
OptionC> If there is an uneven load across the series cells.
OptionD> If the rate of attempted discharge (Watts or Amps) is too fast for the battery's present condition.
OptionE> If those voltage points 12vor 10.5v are not correct the specific battery connected to.
In any of those A-E examples a 12v or 10.5v low voltage cut off can still result in a over discharged battery .. be it AGM , LiFePO4, LTO , NiMH , etc.
Many of your "defenses" here can be easily challenged. You mention power density but how is that a yardstick of performance? If I have an AGM battery bank with 5 KWh of usable power (down to 50% state of charge) and you have 5 KWh of usable LiFePO4 power (down to say 20% state of charge), you might have a higher power density but we both have 5 KWh of usable power so who cares about power density?
You mention 5 options (A thru E) of possible ways to overdischarge a battery bank with references to series connected cells. An easy way around those issues is to just parallel connect 12V batteries. For example, I could use a 12V 100Ah battery in parallel with a 12V 33Ah battery (both AGM) and if done correctly, they will both drain about equally (down to 50% State of charge for example). The combo will have MORE power than just the 100Ah battery alone.
Option D is exceptionally wrong. There is actually a flaw in the 10.5V cutoff in many inverters, however this flaw is more pronounced if the load is too small, not too large. Your description stated you can possible over discharge a battery bank if the discharge rate is too fast for the battery. That is actually backwards. If the battery is old and tired, it will immediately complain about the heavy load and likely dip below 10.5V, thus shutting off the inverter. If the load is high on a healthy battery, it will likely do it for a while, then shut off the inverter MUCH quicker than if there was a very light load, and then rebound back to a MUCH higher voltage such as 12.0 or even higher....
The problem comes in when there is a very light load on an inverter. That is because 10.5V low voltage cutoff with a very light load will actually put the battery bank in an over discharged state. This is the actual case when "automated" protection can actually fail but you did not mention this one. For example, imagine if I used a small 12V inverter and the only load on it was the inverter itself (let's say 6 measured watts which mine tested at), and a 0.5W LED nightlight (a valid test). That setup will drain the battery bank to a MUCH lower state than some heavy load of say hundreds of watts. This is because there is less voltage sag under load and thus less voltage "rebound" after the load is removed. Try it sometime on an old AGM battery not worth much. The 10.5V might spring back to 11.8V for example and that is bad since it is below 50% state of charge. That same battery with a heavy load would likely spring back to 12.0V or more. This is a flaw of many inverter low voltage cutoffs. They should NOT go by voltage alone (such as 10.5V) but rather a function of both voltage and load. Under a very light load, the cutoff should be more like 11.0V or maybe even higher. This "table" of load/voltage combinations should be part of the cutoff and referenced in real time.
As before .. you had many items for me to respond to .. so this will be a little lengthy .. again I used "---" to try and identify groups / or sections.
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Power density is one of the metrics which battery performance is measured .. all over the world .. you don't have to like it .. but that it is one of the real metrics of battery performance that is reality .. no matter what your personal opinion about it is .. we can discuss some of the reasons why it matters more in some applications and less in others .. but in the end .. if you personally choose to disagree (that's fine it's your life) , but the rest of the world won't care .. and power density will continue to be one of the metrics which battery performance is measured.
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That having been said .. you also seem to be confusing / misusing some of the concepts being discussed .. so (for the sake of anyone else whoever reads this) I'll start there clear up a bit , and work my why up.
power and energy :
Energy (calories , wh , joules, etc) .. is the capacity to do work .. if you want to move a stationary object .. or stop moving a moving object .. either would require energy .. if you want to change the temperature of an object up or down that also requires energy .. etc .. etc.
Power (watts , HP , BTU , etc) .. is the rate of energy per unit time .. how fast is the energy being spent , consumed , etc.
.. what this means is that .. 5 kwh is a measurement of energy .. it is not a measurement of power.
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Next Density (Power or Energy)
Density of either power or energy can be measured either .. by volume .. or .. by mass.
power density by volume might look like Watts / Liters
power density by mass might look like watts / kg
energy density by volume might looks like wh / Liter
energy density by mass might look like wh / kg
Therefore:
A battery with lower power density by volume .. will need more space to be able to supply the same total watts of power.
A battery with lower power density by mass .. will need more mass (weight) to be able to supply the same total watts of power.
A battery with lower energy density by volume .. will need more space to be able to supply the same total Wh of energy.
A battery with lower energy density by mass .. will need more mass (weight) to be able to supply the same total wh of energy.
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Next .. to finally get to answer your question "who cares about power density?"
In my last response to you .. someone reading what I wrote in close detail .. might notice .. I gave two different examples of concept:
A stationary application (solar/wind/etc) .. and .. A mobile application (Scooter,HEV,BEV,etc) .. these different applications care differently about power or energy density.
Usually .. Stationary applications don't care as much about space or weight costs .. it still matters .. the client only has a fixed sized room available , or the floor under it is only rated for so many kg of weight , etc .. but usually it matters less than it does in mobile applications.
For example take .. 5kwh of usable energy mentioned above .. with enclosure , wiring , etc.
AGM version .. might end up weighing around ~800 Lbs.
LiFePO4 version .. might end up weighing around ~120Lbs.
In the vast majority of mobile applications .. such as HEV, BEV, etc .. moving ~800lbs instead of ~120Lbs .. for the same ~5kwh of available energy .. the lighter is much better , because it will eat less of that 5kwh to move .. thus it will have a longer range from the same 5kwh of energy .. which will also mean it will be more energy efficient and cost less to fuel it per mile traveled .. it also means the heavier vehicle will have less net acceleration , as more of it's motor power is spent moving the extra weight .. and that means it don't be able to climb as steep of hills ... etc.
Now in a stationary application it might not matter as much .. for example that ~800 Lbs in some places (like the roof) , might not be a good idea .. many other locations (like cement floor) will have no trouble with supporting that weight .. so the stationary application still cares .. and the vastly heavier battery still has a con to it's much higher weight .. even if it isn't as much of a con as it would be in a different application .. but either way .. it is still a metric used to evaluate the performance of the battery in the application.
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Responding to your :
"You mention 5 options (A thru E) of possible ways to overdischarge a battery bank with references to series connected cells. An easy way around those issues is to just parallel connect 12V batteries."
no .. your suggestion will not 'get around' any of those 5.
1st one has to understand .. there is no single cell battery chemistry in the world that gives 12v .. a so called 12v battery is itself (internally) a group of multiple battery cells connected in series .. The voltage profile for AGM would require 6cells be put in series to get a 12v AGM battery .. the voltage profile for LiFePO4 would require 4cells be put in series to get a 12v LiFePO4 battery.
The paralleling method you describe .. is effective for paralleling individual cells .. but .. wired as you described .. series 1st to get to 12v then parallel afterward .. that wiring method will not allow the paralleling method to offer any protection to the battery cells that were 1st wired in series to get the 12v.
Bellow is an Example .. of a AGM battery wired as you described .. but can still get over discharged if pulled down to a net overall 12v or 10.5v.
Of the 6AGM cells wired in series .. needed to get to that 12v .. what if .. 5 are the 100Ah you listed .. but 1 of those cells is is only 50Ah .. all 6 together in series still give a 12v battery .. but when you try to pull all 6 together down to just ~50% target you listed .. you pull 50Ah from all 6 cells .. well one of them only had 50Ah total .. it just got pulled down to 0% SoC .. And while that one cell's voltage drops off .. the other 5 cells in the 6 series pack all still have voltage.
We can do the same if we had 1 of the 4 LiFePO4 significantly lower capacity than the other 3.
thus .. all 5.. A-E methods would still work .. although I still don't know why someone would want to do so.
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Responding to your :
"Option D is exceptionally wrong"
You described a 100% perfectly valid additional way it can happen .. adding 1 more to the list .. up to 6 ways now with your Option F .. although .. I still don't know why someone would want to do so.
I also think you misunderstood the part of that comment of mine where I wrote "for the battery's present condition"
The rate of power watts .. or the rate of current amps .. that is 'safe' , ie not harmful to a battery .. depends on the batteries present condition.
For example .. a battery very cold .. is different from a room temperature battery .. just like a very hot battery is different from a room temperature battery .. or a unmatched pack of batteries is different from a well matched pack of batteries .. or a unbalanced pack of batteries is different from a well balance pack of batteries .. etc.
Take out all the "uh"s and this video would be a lot shorter.