3v? Wow. You will use hardly any capacity. I use a victron smart shunt and I still have about 150a left in a 400a pack at 3v per cell. That's still a lot of useful energy ⚡ I typically discharge to 2.8v at which point, I have 80a left in the battery bank which is manageable for a 400a battery pack. I think the cells are safe and in a good window at 2.8v The danger is discharging to 2.6v often which could lead to damage. The bms cut off is at 2.5v
@@wole04 interesting! Check the discharge curve on your cell chemistry. The curves on my lefepo4 drop like crazy below 3v, meaning there's not much capacity below 3v.
Nice analysis and presentation, thanks! In case you are still into these studies (or already done it :), it would also be interesting to see a similar set charge charts for multi-cell packs with BMSs, especially, understanding how the different cutoff voltages affect the BMS ability to keep the pack balanced.
041122/0247h PST Thank you for the presentation. I have watched this video long time ago and I'm watching again. I fully support your theory of charging LiFePo4 Battery (Cells) @3.40v~3.50v, which will bring battery charge to 96%.(13.6v~14.2V). I have practiced this for almost 4 years and am very satisfied with the results. There's no BULGE no deformation and I don't believe in COMPRESSION. Thank you again. 73s...
if i only has old inverter (48v/lead acid-agm) that has Bulk and Float charge, can i safely set the bulk voltage at 56V and 55.4V for float voltage to my 16s lifepo4 batteries?
WoW! I've never seen such an I depth analysis of the charging/discharging cycle regarding capacity. Kudos to you, this is good stuff! I'm going to lower my charge voltage ti 3.45v. Excellent video! Thanks for sharing.
You got skills! Yes there isn’t much capacity to gain charging the cells to their max voltage. But at the higher cell voltages is where balancing should be done.
@@eksine it’s just a label. Semantics. The absorption phase is used for series-packs of cells to allow the balancer to do it’s thing. Of course single-cells don’t need an absorption phase, per-se.
@@frodev728, it really has nothing to do with how many cells in series or even parallel. But you’re right that “absorption” is just another name for the CV stage, that tell you even though it at max voltage during charge, its not fully charged, and if you end the charge just when CV (absorption) stage begins, the battery voltage will quickly drop to the voltage corresponding to its SOC, which might be 80% if the CC stage was 0.25C. Many reserve the term “Absorption phase” for chemical batteries like Lead Acid that really need to be held at a certain peak voltage to complete a chemical reaction that won’t fully complete at lower voltages. Since lithium batteries are not chemical batteries, they don’t need to be held at a high voltage. You can charge them to 80% each time and it will last longer, but doing that to lead acid will kill it fast. But when discussing Lithium cells, especially LiFePO4 with such a flat SOC voltage curve, whether its called CV or absorption is not important but rather the effect of that stage at different peak charge voltages. As we know, the intercalation rate during CV/absorption is related to the voltage differential. So using the max voltage that doesn’t immediately damage the cell finishes that stage faster. 3.45v is only 0.15v above the 90% SOC voltage (3.3v) so it will take much longer to get that next 5% than using 3.65v, which is 0.35v higher. Armed with this basic foundation, a person can size his battery to match the application and desired life expectancy. If you want it to last 8000 cycles, charge it slow to 70%. No absorption stage because it never reaches CV voltage. But if you need something that can capture and store energy from the grid at super duper off peak rates of $0.01/kwh but that only last 3 hours then you need to use CC of 2C and CV of 3.65v before rates go back to $1/kwh. Lol However if i know i have 8 hrs to charge, i will set CC to 0.2C with CV of 3.65v so it will will be fully charged but only for 2 hrs. It really depends on the application, budget and other factors. Videos like this help you decide what’s best for you.
@@imho7250 ok I know all of that and of course it’s true, but my point about absorption phase, admittedly this is a misnomer, is that using the “absorption phase” (constant voltage) to hold the voltage above the “balance start voltage” of the balancer to allow the cells to be put back in balance is a useful and necessary strategy. Doing that is ONLY necessary if you have 2 or more cells in series, because by definition any less than that (namely one cell) will always be “in balance” because it’s the only cell.
It all depends of the age and capacity of the cells. 3.4v is my preferable max voltage. With the icharger duo 4010 the energy can be recovered into another cell instead of wasting it into heat and the graph charter including the charging logarithms is included and can be downloaded to a pc for better visual.
It would be great to see the 3.5v comparison....it is such a big difference between 3.45 and 3.55, I have no idea how 3.5 would look. Thanks for this video it is very helpful. It would also be good to have a more detailed view of the last part of each curve, to try and see where the best tail current cut off level would be for ending absorption phase on charge controller. Thanks again!
Thanks for answering this question, it seems charging to a lower max voltage appears beneficial the same as Lipo/Li-ion cylindrical cells. One of the reasons I like my turnigy reaktor rc chargers - they allow you to change the per cell end voltage in the settings.
Fantastic vid! Thanks for the effort and knowledge. Please post info or added vid (I'd really like a vid) on the equipment used, especially the Arduino and connected stuff
@@SolarEngineering Thanks for adding the links. I hope you do produce a vid on building the tracker, even a short vid referring us to where you got the idea and parts.
I have my solar Mppt controller set to 3.45V boots mode for 2 hours and then float mode on 3.35V. Boosts return is 3.25V. Active JK balancer starting at 3.40V for top balancing. Took quite a while (a week) to initially balance. Seems fine so far.
That was an excellent test. Thank you for taking the time to show the difference in capacity for the different max charge voltages. Something that is hard to say is how much battery life is increased by choosing to charge "low and slow". I think if the charge voltage is kept low and we only use the middle 80% of battery capacity, the life will be increased dramatically. I wish there was a way to show this.
You will be using a BMS so you do not need safety margins as the BMS should stop charging when any cell gets to say 3.55V. Lithium batteries of any type do not like absorption and float charging so when any cell gets to set limit (I prefer 3.55V) then charging should completely stop until battery is discharged enough to re-enable the charging. It only takes seconds to get from 3.55V to 3.65V so not quite sure how you did the 3.55 and 3.65V test same with 3.45V it should not take long if current was maintained to 5A. Your wires where to high resistance and thus the reason for this sort of results. You should use much thicker and shorter wires or have separate voltage sense wires so 4 wire measurement.
Nice test and yes, going left or right at both knees definately shortens your battery life AND will not give you more that 5-10% extra capacity. Running these cells under high current loads is also dangerous because you will dive deep in both of them with risc of damaging your cells. So anything between 2 and 3,4/3,45V will be good enough is my opinion. Kudo's for your programming with arduino; I am a bit jaleaus to not have these skills. Having the advantages of all these smart and tiny helpers would help me greatly, specially when you want to bottom balance cells and having a cell bouncing back to a higher voltage after stopping discharge it to say 2,6 Volts....
@@SolarEngineering yeah, but a Salsa (as a metafor) never can be performed as well as by somebody who has dance in it's bones, how hard you practice and try. If I would say a wiener waltz, then you probably would apply too 😁😁😁
In my case, I see, that voltage over 3,5v per cell give us faster charge, but deviation between cells increase more and more, so Neey Smart 4Amper active balancer does a lot of job for balance higher cells. Charge at nearly 3,430 never give any deviation more then 0,010mv, and there is no need for using Active Balancer, only bms (Daly 200A 200mv balace current) is sufficient.
For solar, I'll probably set for 3.5 volts per cell. For floating, I set for 3.475. 3.65 volts should be considered a "withstand" voltage, rather than a "finishing" voltage for charging. While it's safe to discharge to 2.5 volts per cell, I find that the voltage starts rolling off sharply below 3 volts per cell. For day to day cyclic use, I recommend charging to 3.5 volts, then discharging only down to 3 volts even per cell. That will give you ~95% capacity usable, while minimizing degradation.
If I understand this correctly, the longer charging time is due to the lower voltage causing a less aggressive charge current as the battery reaches the final voltage, thus the tail current (typically 2-3%) aka the ‘we can stop charging now’ current must be set at a lower percentage (of the initial CC value) in order to achieve near 100% SOC at the lower final voltage? It looks like finding a sweet spot between 6-10Hrs for 0.2C is warranted but at a voltage that is high enough to trigger the internal BMS of multicell battery such as a 4 cell 12.8V 100Ah LiFePo4 unit. If I’m missing something input would be appreciated!
Just realized that tail current sensing for end of charge can be left as it is. It’s just going to longer to get there. Adjust ‘absorption’ aka CV phase accordingly I would guess.
3.55v for the win long term. Beyond this, you start ripping the iron from the phosphate, forming pyrophosphates and decomposing the electrolyte in the process, this does not become a critical issue until you exceed about 3.7V.
My iMAX B6 Multi Charger is 3.6 volt , on the lifepo setting. you can put it on 5 amp charge , but it automatically decreases as it charges. like most lead acid chargers do when charging lead acid.
спасибо! относительно недавно интересуюсь этой областью, ищу все, что можно посмотреть по этой теме, отличный видос! судя по акценту, переводчик для камента не понадобится )
If you have time you could charge to 3.45V and keep it there 45-60min in an absorbtion phase. After that you have 98% capacity. You could even go to 3.4V but then absorbtion phase takes 4-5h and remember to give the BMS a chance for balancing. At 3.45V you are on the safe side and have 0.4V room for balancing
Напряжение имеет смысл в случае лиферов, кмк как однозначный предел. Уменьшать его ниже 3.6В, имеет смысл во всяком случае на этапе буст-зарядки, когда ток максимальный, это в отдельных случаях спасет от опасного разбаланса сборку (если балансир не тянет, перегрев и т.п.) и соотвественно срабатывания защиты BMS. Вполне можно обойтись заниженным напряжением в идеальных условиях, когда солнце грубо говоря 8 часов дает избыточную генерацию в систему. Но если на произвольном объекте полный заряд критически важен, а солнце то и дело скрывается за облаками, пониженное напряжение повредит системе уже потому, что будет исключен максимальный ток заряда в момент пиковой генерации. А тест познавательный, такие-же графики на промышленном тестировщике можно наблюдать.
Help; When charging on my large lead acid charger in my UPS inverter/charger, the charger does not recognize charge state and taper the AMPS DOWN as it gets full, like when it is charging the deep cycle lead. With my lifepo4 battery , it just stays charging at 40 amps the whole time. This is a problem because as the cells near full, they start to charge up faster, lose balance and always shut down due to a cell over voltage. Thus never getting a "full " charge .I am lucky to get 60%.. with my solar charge controller and other lead acid chargers I have , it works like a lead acid would and tapers the AMPS DOWN as it gets full. Why?
Assuming that you did top balanced cells, I would install an active balancer that will prevent BMS from shutting down the pack. Depending on size of your battery pack, I can recommend few different balancers.
Another idea, have you thought of trying the same with Li-Ion batteries, NMC ones? Curious to see how 4.0, 4.10 and 4.20 behave. I think it will make a bigger difference there due to the charge/dischange curves. Could try with a couple 18650's in parallel to get an idea with a 10ah or so capacity.
Great video and many thanks! Btw, the link for the Capacity Tester on Ali Express doesn't work. I just get to their front page. What is the name of this tester?
Does 57.6 volts refer to the charging speed or the energy storage limit of the battery? If someone sets it to 56 volts instead, will they get the same battery backup as with 57.6 volts?
I just saw this vid. I'm confused as to why, if you are charging at the same current, it took longer to end up at 3.55V than 3.65 volts? The 3.65 volt graph should show reaching 3.55 volts at some point, and it would have to be less than the time to 3.65 volts.
hmm,? I have just purchased 8- 500ah 3.2v Lifepo4 cells, which will eventually be configured into two 2 - 500ah 12v "batteries". I will connect the cells in parallel to balance the cells for their first charge to balance the cells. Charging at 5a it will take 33 days to fully charge the cells.! Have you any advice.?
The max charge is not used for charging it is primarily used for cell balancing. Most balancing circuitry on the market is carry over form LI-ION or NMC and LI-POLY which do not have a flat voltage profile like LFP. Because of this the only time they see enough of a difference to beging balancing is when 1 LFP cell is high enough to trigger balancing. At 3.45v your effectively full charged, but this voltage is not sufficient for balancing hardware.
What's your opinion on connecting batteries from different manufacturers with different BMS's in parallel? I have some 12 volt 200AH batteries (100AH cells) 12 volt 300AH batteries (150AH cells) all prismatic type cells and also have some 12 volt 300AH batteries (cylindrical cells), I would like to connect some together to make a bigger bank but I keep getting different opinion on videos
I personally don't see any problems with connecting different packs into parallel (when packs are not too far in capacity from each other, like 5X diff). Would like to hear and discuss what is the potential issues could be.
@@SolarEngineering There's no downside to this at all. Has been tested and demonstrated over at Andy's Off Grid Garage channel using "extreme" examples. one tiny cell vs a big battery pack paralleled, they both discharge equally regardless of size. If the large pack uses 10% of it's available capacity, so does the smaller one. doesnt matter if its 1000 mAh alongside a 1000 Ah, the little one will be at 900mAh and the other at 900 Ah after a 10% discharge. :)
Nice work! I hadn't gone to that level before, but always kept mine at 3.60 or lower. Would be interested in the links for the arduino gear used or a video on it even.
I'm not technically battery savvy, but do these charge/discharge numbers apply to just the LiFePos you're testing or to all LiFePos at all voltages? I have a 2015 48V 21Ah LiFePo4 Chinese escooter battery with a typical plug&play charger AND an adjustable Grin charger. What specs make for the best charge rates of this battery? BTW, I generally charge it to full and use it right away. I also store it for the winter at 50%soc.
At 3.45 OCV a LiFePO cell is 100+% full - SoC! But sometimes you have to go further for Balancing as the voltage below 3.45V is not telling you anything about the SoC status - you need the steep curve part in the SoC/Voltage Chart for Balancing - otherwise you dont need to go any higher than 3.4 V.
Im new to LifePO4, but really, how many type of it? @Off-grid system Andy has tested it best on 3.45V. Maybe every different brand or class really matters?
finally what voltage do you suggest for 16 cell 280a battery pack for daily home use ? my cells after 3.4 begin to to be not equalized and 5-6 cells go fast to 3.5 , i think it's better to have an absoption around 3.4, correct?
I've got a question... my pack is 24s so charges to like 86.7 or 87 volts and it used to stay at 87 volts. Now as soon as I unplug the charger the voltage begins dropping until it gets to the nominal voltage where it stays and then from there I can use my pack but idk why it's doing this.im losing like half my usable volts
@@MotoAlias ah, that's not normal. Is that brand new pack? Do you have anything else attached to the pack that could draw energy? How quick is voltage drop?
@@SolarEngineering drops by .1 about every 5 seconds... like when I unplug the charger you can watch it drop .1 till it reaches the cells nominal voltage then stops. I guess it could've had a paristic draw going to my headlight but I've disconnected that and still same problem... the pack isnt new I'm afraid I drained it too low. I had 3 cells that were swollen and I replaced them. But I guess even tho the other cells didnt swell perhaps they're all ruined.
if i only has old inverter (48v/lead acid-agm) that has Bulk and Float charge, can i safely set the bulk voltage at 56V and 55.4V for float voltage to my 16s lifepo4 batteries? or i should change to other voltages?
@@SolarEngineering Do a Video: - ---I hear you, apparently so, but somehow i think that,say, a 30 Ah and a 280 Ah LiFePo4s will have different graphs for voltages and SOCs; i mean,at the mV level, possibly even at the centiVolt?; Do a video on that; Even from different manufacturers,different materials and chemicals, i see different recommendations. ( also i just read that CALB recommends that the very first charge be to 3.80 volts, (then to the 3.65), i wonder why).
Does it not mean that over time the voltage gap between the cells will drift more as there not hitting max voltage for the BMS to balance them? Also when there discharged if there is a big difference then won't the lowest one be below minimum voltage?
Good question, at 3.5V per cell v diff will show up, so BMS will have a chance to balance cells. Didn't get about low voltage (BMS will disconnect pack if any cell drop below preset voltage)
nice setting, nice test ...however I just don't get why the charging time with 3,45V compared to 3,65V is increasing (instead of getting less) (almost double) with same charging current ...why that?
Hi, I have 8 Pylontech LiFePO4 48v 50ah (2.4kWh) batteries with the charge voltage set at 53.3 volts in the inverter/charger settings. Assuming these are 15 cell batteries this gives a charge voltage of 3.55 volts per cell, would you consider this the optimum charge voltage for battery longevity verses charge times. This is the settings set by the system installer 3 years age, If I understood your excellent video correctly a lower cell charge voltage of say 3.50 volts takes longer but extends cell lifespan, i'd drop the cell voltage as for 80% of the year the battery is fully charged by midday and for the other 20% I top up the battery during the night on cheap rate grid power. Thanks in advance for any advice.
Hi, I'd double-check how many cells are there (15 or 16). Also based on my tests I would recommend lower voltage to 3,5V per cell. You'll still get the same charging speed and capacity, but the "safety" range will be a little bit more bigger.
@@SolarEngineering Hi thanks for your reply, I just checked, they are 15 cell batteries. So following your advice I should reduce the maximum charge voltage to 52.5 volts for added protection/safety of the modules, i've tried to prolong the battery lifespan by never discharging below 40% SOC, rarely below 60% SOC in daily use, am I helping doing this? There seem to be a consensus around this practice of limiting DOD to extend battery life so i'd be interested to have your take on this. Once again thank you for any views and information you provide.🙂👍👍👍
@@ambientfish1369 52.5 sounds right then. I think 40% SOC is too generous for LiFePo4, you could use 80% of it's capacity and it's considered as light use, also important C rating you charge and discharge (smaller rating = longer life). (My statement about 80% is based on information I read on multiple resources, I didn't test it since it's taking years).
@@SolarEngineering Thank you bro for the replies I really appreciate your valuable time. I do try to restrict the draw from the modules, most of the day the house is using solar power direct from the panels, at night average draw from the battery is 220 w at circa 4-5 amps with an very occaisional 2000w draw of short duration for the oven (20 mins) max, I know it is worth being careful in how you utilise batteries and I want them to last as long as possible, thank you again you have been a big help🙂👍👍👍🏴
You don't need to float Lithium Iron Phosphate Batteries. Float voltage was from the days of Lead Acid Batteries that needed to be floated to prevent sulfation. Floating a LFP battery will shorten the lifespan of the battery as you are continuously running low level current (charging) into it.
Hello ,and thank you for your video, i have 105ah eve 8 cells, So is 24v baterry, what is the best to get charge? I have set on my bms 3.6v per cell, and 28.8v total maximum charge. Is good? Or set at 3.55v? Thank you
Hi, Good job!! I have a LiFePO4 in my motorhome. I need that it charge as soon as possible and that MPPT keeps the battery almost 100% all the time. Then I have: Bulk 14.2v. Absortion: 13.4v Re-bulk: 13.3v Do you think it is correct? Then When I have my motorhome parked It is plugged to 220v Then in that case I only need to maintain battery, so My paramters are 13.4v 13.00v rebulk 12.8v What do you think about that?
i need help please, i have 8 lifepo4 cells eve 105ah (my battery is 24v 105ah ) i have a bms , i want to charge to 3.55v per cell, is ok to change the settings only in bms from 3.65v to 3.55v and the sum high protect from 28.8v to 28.4v ? thats correct? but my mppt charge controller is on 28.8v , i must change and the charge controller to 28.4v ? or just on bms and is ok? please help, thank you very much
I have 2 lifePO4 12v 8Ah I bought the first of this month. I bought a charge you have to set type of battery number of cells, voltage, etc. I tried to see the charger work. When I hook either battery up and try to start the charge I get a cell warning on both and no charge. My other charger gives me a cell balance problem. What do you think? I just got one of the Miady 20ah batteries today. The charger is at my office so haven’t had a chance to try it with either charger.
Hi, I need more details: battery model, charger model. Do you connect battery balancing leads to the charger? If not then here is why the charger shows an error.
@@SolarEngineering the charger is a HiTec RDX1 Multicharger. I don’t see how to setup balancing for the battery since can’t get to the individual cells. I have an imax charger as well. I didn’t know at the time that Bioenno sold a charger that didn’t require the balancing would have bought it. But, now I hate to buy another charger. I’m using these batteries for portable Ham Radio operation.
But most LifePo4 chargers don't work with constant voltage , but they try to push as much current as possible until the voltage hit 3.xx volts per cell , So should take the same time to charge to 3.4 , 3.45 , 3.5 , 3.55 or may be a little shorter ?
Damn! Would have loved to see this at 3.5 since we saw that massive charge time increase at 3.45. I would definitely not use 3.45v are itll take an insane amount of time to charge.
@@SolarEngineering yep. is that an important fact to highlight when comparing LFP charge graphs? aren't most charge graphs based on resting voltage, not charge/discharge voltage? I feel resting voltage isn't highlighted enough by many people.
So why > 3.45 V? At 3.65 V you gain 0.17 Ah more. That is < 1% of the capacity. If you stress your cells, they get dendrites or deposits. Even this video is 3 years old it has its important results. After viewing Andy & Co i drive my cells from 3.1V (0%) to 3.4V (100%). At these points the LFP-curves increases/decreases very fast. They leave the quasi-linear curve-pattern aka line. My guess: Obviously there is action. And action stresses everything.
Good test but your electronic load cutoff at 2.5V is not accurate as you are not sensing the batt voltage at the terminals. That tester has separate current and voltage terminals for you to sense the voltage at the batt terminals. Hope you use it next time.
Do you feel this causes tests to be inaccurate? I think for this case it doesn't matter, I'm monitoring voltage directly from the cell using Arduino so all graphs are pretty accurate. Load is just discharging cell (same condition for all 3 tests), maybe if I run other wires from cell to load, I'll get a few extra mA, but still, it's going to be the same mA for all 3 tests.
@@SolarEngineering I'm not arguing, just merely suggesting to use a feature that is made available for more AH/WH accuracy. We don't know how much AH or mAH is left in the cell because the cutoff happened earlier than 2.5V. In a 25AH cell with 5A discharge it may not be much but e.g. if you measure your 280AH cells at 20A then you can see a huge difference. And also you can measure an accurate WH with voltage sensing. Anyways your tests itself may be accurate as it's a comparison with the same load.
My LifePO4 cells can not hold 3.35V discharging immediately to 3.3 level. Also not charging above 3.35 (53.6V) level. I think the DOD of my cells 80%. Anyone know reason for this?
@@SolarEngineering Yes. Like you did in this test but for lower voltage cutoff. If you start at a fixed voltage (for example 3.45V) and then do discharge test from 3.45V to 2.75V, another discharge test from 3.45V to 3V and another from 3.45V to 3.25V and see how much energy you get out of the cell. Since discharging to 3.25V instead of 2.75V prolongs battery life but it would be interesting to know how much energy you can get if you cut under voltage sooner
If you don't use the voltage sense leads on the DL24 your results will be a bit off, especially when discharging at over 1A since you can only use 12AWG in those terminals at most. There should be some level of consistency when you're using the same cell over and over set for the same discharge cut off but I'm sure there's variables influenced by the different charging voltages that could impact your result. I'd have to do some testing to see what I can pull from something like an 8Ah Headway with and without sense leads. I think I'll try that right now. Since the max safe charging voltage of LiFeP04 is 4.20V there's really no need to put any safety headroom in place but I really do like 3.55V to 3.60V. Past that the voltage rises so fast that no balancer can handle an out of whack cell and a charge rate that is decently fast which can be very annoying.
@@johnd9763 wrong. You can even Google “safe max charging voltage lifepo4” and you’ll see right at the top 4.20V is listed. You can probably find some decade old literature on the internet for controllers and inverters that mentions voltages well above 3.70V. I found one a couple months ago that was likely from 2010-2012 that had the max voltage for a controller at 4.0V per cell. Wish I could remember the company it’s gotta be an old school one that’s likely still around like Morningstar
I would also like to know that, to perform such test would take years :) Main point is to keep cells away from 3.65V especially when many cells in series (16 for example).
A lot of questions I had about this were answered in this video. I'm glad to have found that someone spent the time to do this.
I just lowered my charge voltage to 3.55V/cell. This seems entirely reasonable and builds in more safety margin. Thanks
I've charged all mine to 14.1 or 3.525v per cell
Maybe i need to slightly raise the voltage?
3.45 is actually best for long term.
Nice work.
I did similar testing and came up with 3.4 to 3.45V Max, also very little point in discharging below 3.0v.
3v? Wow. You will use hardly any capacity. I use a victron smart shunt and I still have about 150a left in a 400a pack at 3v per cell. That's still a lot of useful energy ⚡
I typically discharge to 2.8v at which point, I have 80a left in the battery bank which is manageable for a 400a battery pack. I think the cells are safe and in a good window at 2.8v
The danger is discharging to 2.6v often which could lead to damage. The bms cut off is at 2.5v
@@wole04 interesting!
Check the discharge curve on your cell chemistry. The curves on my lefepo4 drop like crazy below 3v, meaning there's not much capacity below 3v.
3.2 v as standard lower voltage limit is even better. More cycle life.
Thanks for the info, its good to know that we are not loosing that much capacity on 3.45V
The most detailed tests and the best explanations that I've found. Thank you for your work and dedication!
Nice analysis and presentation, thanks! In case you are still into these studies (or already done it :), it would also be interesting to see a similar set charge charts for multi-cell packs with BMSs, especially, understanding how the different cutoff voltages affect the BMS ability to keep the pack balanced.
Thanks for the enlightening presentation!
041122/0247h PST Thank you for the presentation. I have watched this video long time ago and I'm watching again. I fully support your theory of charging LiFePo4 Battery (Cells) @3.40v~3.50v, which will bring battery charge to 96%.(13.6v~14.2V). I have practiced this for almost 4 years and am very satisfied with the results.
There's no BULGE no deformation and I don't believe in COMPRESSION. Thank you again. 73s...
if i only has old inverter (48v/lead acid-agm) that has Bulk and Float charge,
can i safely set the bulk voltage at 56V and 55.4V for float voltage to my 16s lifepo4 batteries?
WoW! I've never seen such an I depth analysis of the charging/discharging cycle regarding capacity. Kudos to you, this is good stuff! I'm going to lower my charge voltage ti 3.45v. Excellent video! Thanks for sharing.
Glad it was helpfull.
You got skills! Yes there isn’t much capacity to gain charging the cells to their max voltage. But at the higher cell voltages is where balancing should be done.
indeed, or just leave enough headroom above the absorption voltage setpoint that balancing isn’t even an issue.
@@frodev728 lifepo4 isn't supposed to have an absorbtion phase
@@eksine it’s just a label. Semantics. The absorption phase is used for series-packs of cells to allow the balancer to do it’s thing. Of course single-cells don’t need an absorption phase, per-se.
@@frodev728, it really has nothing to do with how many cells in series or even parallel. But you’re right that “absorption” is just another name for the CV stage, that tell you even though it at max voltage during charge, its not fully charged, and if you end the charge just when CV (absorption) stage begins, the battery voltage will quickly drop to the voltage corresponding to its SOC, which might be 80% if the CC stage was 0.25C.
Many reserve the term “Absorption phase” for chemical batteries like Lead Acid that really need to be held at a certain peak voltage to complete a chemical reaction that won’t fully complete at lower voltages. Since lithium batteries are not chemical batteries, they don’t need to be held at a high voltage. You can charge them to 80% each time and it will last longer, but doing that to lead acid will kill it fast.
But when discussing Lithium cells, especially LiFePO4 with such a flat SOC voltage curve, whether its called CV or absorption is not important but rather the effect of that stage at different peak charge voltages.
As we know, the intercalation rate during CV/absorption is related to the voltage differential. So using the max voltage that doesn’t immediately damage the cell finishes that stage faster. 3.45v is only 0.15v above the 90% SOC voltage (3.3v) so it will take much longer to get that next 5% than using 3.65v, which is 0.35v higher.
Armed with this basic foundation, a person can size his battery to match the application and desired life expectancy. If you want it to last 8000 cycles, charge it slow to 70%. No absorption stage because it never reaches CV voltage.
But if you need something that can capture and store energy from the grid at super duper off peak rates of $0.01/kwh but that only last 3 hours then you need to use CC of 2C and CV of 3.65v before rates go back to $1/kwh. Lol
However if i know i have 8 hrs to charge, i will set CC to 0.2C with CV of 3.65v so it will will be fully charged but only for 2 hrs.
It really depends on the application, budget and other factors. Videos like this help you decide what’s best for you.
@@imho7250 ok I know all of that and of course it’s true, but my point about absorption phase, admittedly this is a misnomer, is that using the “absorption phase” (constant voltage) to hold the voltage above the “balance start voltage” of the balancer to allow the cells to be put back in balance is a useful and necessary strategy. Doing that is ONLY necessary if you have 2 or more cells in series, because by definition any less than that (namely one cell) will always be “in balance” because it’s the only cell.
It all depends of the age and capacity of the cells. 3.4v is my preferable max voltage.
With the icharger duo 4010 the energy can be recovered into another cell instead of wasting it into heat and the graph charter including the charging logarithms is included and can be downloaded to a pc for better visual.
Been looking for this data tested just like this, thanks!
glad it was helpful
Thanks for doing this test; it answered all the questions I needed to know. Well done!
Glad it was helpful!
It would be great to see the 3.5v comparison....it is such a big difference between 3.45 and 3.55, I have no idea how 3.5 would look.
Thanks for this video it is very helpful.
It would also be good to have a more detailed view of the last part of each curve, to try and see where the best tail current cut off level would be for ending absorption phase on charge controller. Thanks again!
Thanks for answering this question, it seems charging to a lower max voltage appears beneficial the same as Lipo/Li-ion cylindrical cells.
One of the reasons I like my turnigy reaktor rc chargers - they allow you to change the per cell end voltage in the settings.
Fantastic vid! Thanks for the effort and knowledge.
Please post info or added vid (I'd really like a vid) on the equipment used, especially the Arduino and connected stuff
Thanks.
I've added links to Arduino parts. May be will add a video on how to build tracker if more people are interested.
@@SolarEngineering +1 for this
@@SolarEngineering I would like to see a video on how the tracker is assembled my self, Thanks
@@SolarEngineering Thanks for adding the links. I hope you do produce a vid on building the tracker, even a short vid referring us to where you got the idea and parts.
@@SolarEngineering Please let's have a video on the tracker. Thanks for the efforts.
Хеллоу мен. Сэнск фор э гуд ворк энд видео. Кип йор лайк
The only advantage to charge with 3.65v is fast charge /I personally set mine to 3.5v and they are stil going strong after 12 years. 😊
wow, what is the brand of the cells? Did you measure capacity after 12 years?
@@SolarEngineering they have lost about 20% capacity. Later I will take look for the brand name.
The manufacturer number is against the wall and I am not disconnecting and moving it to find it "weighing 120kg". I bought it trough alibaba China
@@catesolarcatamaran252 can you get the info from other source like order page etc?
And can you tell us what for these batteries Ar being used? Is it energy storage? How many cycles it do per year?
I have my solar Mppt controller set to 3.45V boots mode for 2 hours and then float mode on 3.35V. Boosts return is 3.25V. Active JK balancer starting at 3.40V for top balancing. Took quite a while (a week) to initially balance. Seems fine so far.
That was an excellent test. Thank you for taking the time to show the difference in capacity for the different max charge voltages. Something that is hard to say is how much battery life is increased by choosing to charge "low and slow". I think if the charge voltage is kept low and we only use the middle 80% of battery capacity, the life will be increased dramatically. I wish there was a way to show this.
yeah, I wish it too. Unfortunately, tests like that will take years...
thank you. Very usefull video !
Cool test! For me the best is 3.55v! That save the battery a little and no difference with the capacity!
You will be using a BMS so you do not need safety margins as the BMS should stop charging when any cell gets to say 3.55V. Lithium batteries of any type do not like absorption and float charging so when any cell gets to set limit (I prefer 3.55V) then charging should completely stop until battery is discharged enough to re-enable the charging.
It only takes seconds to get from 3.55V to 3.65V so not quite sure how you did the 3.55 and 3.65V test same with 3.45V it should not take long if current was maintained to 5A. Your wires where to high resistance and thus the reason for this sort of results. You should use much thicker and shorter wires or have separate voltage sense wires so 4 wire measurement.
Nice test and yes, going left or right at both knees definately shortens your battery life AND will not give you more that 5-10% extra capacity.
Running these cells under high current loads is also dangerous because you will dive deep in both of them with risc of damaging your cells.
So anything between 2 and 3,4/3,45V will be good enough is my opinion.
Kudo's for your programming with arduino; I am a bit jaleaus to not have these skills.
Having the advantages of all these smart and tiny helpers would help me greatly, specially when you want to bottom balance cells and having a cell bouncing back to a higher voltage after stopping discharge it to say 2,6 Volts....
thanks! Arduino is not so complicated, many online step-by-step tutorials.
@@SolarEngineering yeah, but a Salsa (as a metafor) never can be performed as well as by somebody who has dance in it's bones, how hard you practice and try.
If I would say a wiener waltz, then you probably would apply too 😁😁😁
In my case, I see, that voltage over 3,5v per cell give us faster charge, but deviation between cells increase more and more, so Neey Smart 4Amper active balancer does a lot of job for balance higher cells. Charge at nearly 3,430 never give any deviation more then 0,010mv, and there is no need for using Active Balancer, only bms (Daly 200A 200mv balace current) is sufficient.
Is your daly bms a smart one or just the ordinary? thanks
For solar, I'll probably set for 3.5 volts per cell. For floating, I set for 3.475. 3.65 volts should be considered a "withstand" voltage, rather than a "finishing" voltage for charging. While it's safe to discharge to 2.5 volts per cell, I find that the voltage starts rolling off sharply below 3 volts per cell. For day to day cyclic use, I recommend charging to 3.5 volts, then discharging only down to 3 volts even per cell. That will give you ~95% capacity usable, while minimizing degradation.
If I understand this correctly, the longer charging time is due to the lower voltage causing a less aggressive charge current as the battery reaches the final voltage, thus the tail current (typically 2-3%) aka the ‘we can stop charging now’ current must be set at a lower percentage (of the initial CC value) in order to achieve near 100% SOC at the lower final voltage?
It looks like finding a sweet spot between 6-10Hrs for 0.2C is warranted but at a voltage that is high enough to trigger the internal BMS of multicell battery such as a 4 cell 12.8V 100Ah LiFePo4 unit.
If I’m missing something input would be appreciated!
Just realized that tail current sensing for end of charge can be left as it is.
It’s just going to longer to get there.
Adjust ‘absorption’ aka CV phase accordingly I would guess.
3.55v for the win long term. Beyond this, you start ripping the iron from the phosphate, forming pyrophosphates and decomposing the electrolyte in the process, this does not become a critical issue until you exceed about 3.7V.
Great work ! Maybe you should make a video about the Aurdreno and the VA tracker. That would be great !
Thanks, here is video: th-cam.com/video/EnlKS4hdwk8/w-d-xo.html
My iMAX B6 Multi Charger is 3.6 volt , on the lifepo setting. you can put it on 5 amp charge , but it automatically decreases as it charges. like most lead acid chargers do when charging lead acid.
спасибо! относительно недавно интересуюсь этой областью, ищу все, что можно посмотреть по этой теме, отличный видос! судя по акценту, переводчик для камента не понадобится )
)) добро пожаловать на канал
спасибо большое
If you have time you could charge to 3.45V and keep it there 45-60min in an absorbtion phase. After that you have 98% capacity. You could even go to 3.4V but then absorbtion phase takes 4-5h and remember to give the BMS a chance for balancing. At 3.45V you are on the safe side and have 0.4V room for balancing
Amazing info!
cool test. I am only charging to 3.4V
Thank You, VERY helpful and informative.
Напряжение имеет смысл в случае лиферов, кмк как однозначный предел. Уменьшать его ниже 3.6В, имеет смысл во всяком случае на этапе буст-зарядки, когда ток максимальный, это в отдельных случаях спасет от опасного разбаланса сборку (если балансир не тянет, перегрев и т.п.) и соотвественно срабатывания защиты BMS. Вполне можно обойтись заниженным напряжением в идеальных условиях, когда солнце грубо говоря 8 часов дает избыточную генерацию в систему. Но если на произвольном объекте полный заряд критически важен, а солнце то и дело скрывается за облаками, пониженное напряжение повредит системе уже потому, что будет исключен максимальный ток заряда в момент пиковой генерации. А тест познавательный, такие-же графики на промышленном тестировщике можно наблюдать.
great! Thanks!
Help;
When charging on my large lead acid charger in my UPS inverter/charger, the charger does not recognize charge state and taper the AMPS DOWN as it gets full, like when it is charging the deep cycle lead. With my lifepo4 battery , it just stays charging at 40 amps the whole time. This is a problem because as the cells near full, they start to charge up faster, lose balance and always shut down due to a cell over voltage. Thus never getting a "full " charge .I am lucky to get 60%.. with my solar charge controller and other lead acid chargers I have , it works like a lead acid would and tapers the AMPS DOWN as it gets full. Why?
Assuming that you did top balanced cells, I would install an active balancer that will prevent BMS from shutting down the pack. Depending on size of your battery pack, I can recommend few different balancers.
So if you need to charge the battery fast.( to small battery) use 3.65 if you want youre battery to live longer use 3.55v.
Another idea, have you thought of trying the same with Li-Ion batteries, NMC ones? Curious to see how 4.0, 4.10 and 4.20 behave. I think it will make a bigger difference there due to the charge/dischange curves. Could try with a couple 18650's in parallel to get an idea with a 10ah or so capacity.
Great video and many thanks! Btw, the link for the Capacity Tester on Ali Express doesn't work. I just get to their front page. What is the name of this tester?
updated the link, try it now
Good info, thank you
Glad it was helpful!
Does 57.6 volts refer to the charging speed or the energy storage limit of the battery? If someone sets it to 56 volts instead, will they get the same battery backup as with 57.6 volts?
I just saw this vid. I'm confused as to why, if you are charging at the same current, it took longer to end up at 3.55V than 3.65 volts? The 3.65 volt graph should show reaching 3.55 volts at some point, and it would have to be less than the time to 3.65 volts.
hmm,?
I have just purchased 8- 500ah 3.2v Lifepo4 cells, which will eventually be configured into two 2 - 500ah 12v "batteries".
I will connect the cells in parallel to balance the cells for their first charge to balance the cells.
Charging at 5a it will take 33 days to fully charge the cells.!
Have you any advice.?
checkout this video th-cam.com/video/X_ucHHnh4Ik/w-d-xo.html from 7:40
The max charge is not used for charging it is primarily used for cell balancing. Most balancing circuitry on the market is carry over form LI-ION or NMC and LI-POLY which do not have a flat voltage profile like LFP. Because of this the only time they see enough of a difference to beging balancing is when 1 LFP cell is high enough to trigger balancing.
At 3.45v your effectively full charged, but this voltage is not sufficient for balancing hardware.
What's your opinion on connecting batteries from different manufacturers with different BMS's in parallel? I have some 12 volt 200AH batteries (100AH cells) 12 volt 300AH batteries (150AH cells) all prismatic type cells and also have some 12 volt 300AH batteries (cylindrical cells), I would like to connect some together to make a bigger bank but I keep getting different opinion on videos
I personally don't see any problems with connecting different packs into parallel (when packs are not too far in capacity from each other, like 5X diff).
Would like to hear and discuss what is the potential issues could be.
@@SolarEngineering There's no downside to this at all. Has been tested and demonstrated over at Andy's Off Grid Garage channel using "extreme" examples. one tiny cell vs a big battery pack paralleled, they both discharge equally regardless of size. If the large pack uses 10% of it's available capacity, so does the smaller one. doesnt matter if its 1000 mAh alongside a 1000 Ah, the little one will be at 900mAh and the other at 900 Ah after a 10% discharge. :)
@@zoe..d thanks for the info
Nice work! I hadn't gone to that level before, but always kept mine at 3.60 or lower. Would be interested in the links for the arduino gear used or a video on it even.
thanks.
I've added links to Arduino parts. May be will add a video on how to build tracker if more people are interested.
@@SolarEngineering Yes, I want to know how to build that tracker too - Does it measure both ways (in/out) - and know the difference? :)
Buongiorno. Ottimo test . Io carico i miei 20 kw 4x5 a 4.41V per cella . Una volta al mese a 4.5 . 2 anni senza problemi.
4,41v????
I'm not technically battery savvy, but do these charge/discharge numbers apply to just the LiFePos you're testing or to all LiFePos at all voltages? I have a 2015 48V 21Ah LiFePo4 Chinese escooter battery with a typical plug&play charger AND an adjustable Grin charger. What specs make for the best charge rates of this battery? BTW, I generally charge it to full and use it right away. I also store it for the winter at 50%soc.
At 3.45 OCV a LiFePO cell is 100+% full - SoC! But sometimes you have to go further for Balancing as the voltage below 3.45V is not telling you anything about the SoC status - you need the steep curve part in the SoC/Voltage Chart for Balancing - otherwise you dont need to go any higher than 3.4 V.
Wrong
Wrong@@shawnd567
Are there any data regarding how much of batter’s life or charge cycles is recovered/saved when we charge to 3.45 vs 3.55 or 3.65
Im new to LifePO4, but really, how many type of it? @Off-grid system Andy has tested it best on 3.45V. Maybe every different brand or class really matters?
Curious, what dll did you use for the INA260, the adafruit or some other ? I have had mixed results with the INA units.
here is video where I'm building tester: th-cam.com/video/EnlKS4hdwk8/w-d-xo.html
@@SolarEngineering I found it. thank you.
finally what voltage do you suggest for 16 cell 280a battery pack for daily home use ? my cells after 3.4 begin to to be not equalized and 5-6 cells go fast to 3.5 , i think it's better to have an absoption around 3.4, correct?
3.45-3.5V per cell, with a 3.4V per cell charger might not go at full power while charging pack (it will reach 3.4 and will float there)
I've got a question... my pack is 24s so charges to like 86.7 or 87 volts and it used to stay at 87 volts. Now as soon as I unplug the charger the voltage begins dropping until it gets to the nominal voltage where it stays and then from there I can use my pack but idk why it's doing this.im losing like half my usable volts
LiFePo4 cells will drop voltage after charging to ~3.45-50V per cell, so in your case 82.8V - 84V. But don't worry capacity is still there.
@@SolarEngineering ya but mine seems to drop further than that like to the point that each cell would be at nominal voltage 3.2
@@MotoAlias ah, that's not normal. Is that brand new pack? Do you have anything else attached to the pack that could draw energy? How quick is voltage drop?
@@SolarEngineering drops by .1 about every 5 seconds... like when I unplug the charger you can watch it drop .1 till it reaches the cells nominal voltage then stops. I guess it could've had a paristic draw going to my headlight but I've disconnected that and still same problem... the pack isnt new I'm afraid I drained it too low. I had 3 cells that were swollen and I replaced them. But I guess even tho the other cells didnt swell perhaps they're all ruined.
@@MotoAlias I'd disassemble the pack (or disconnect cells) and test few cells individually.
if i only has old inverter (48v/lead acid-agm) that has Bulk and Float charge,
can i safely set the bulk voltage at 56V and 55.4V for float voltage to my 16s lifepo4 batteries?
or i should change to other voltages?
56V should be good enough for 16S LiFePo4, make sure your BMS has cutoff voltage set at 3.65
Nice, but are ALL Lifepo4 chemistries, brands, sizes, etc, the same? i Mean, a 280 Ah will behave the same as this one?
It is same for all Lifepo4 chemistry
@@SolarEngineering Do a Video:
- ---I hear you, apparently so, but somehow i think that,say, a 30 Ah and a 280 Ah LiFePo4s will have different graphs for voltages and SOCs; i mean,at the mV level, possibly even at the centiVolt?;
Do a video on that;
Even from different manufacturers,different materials and chemicals, i see different recommendations.
( also i just read that CALB recommends that the very first charge be to 3.80 volts, (then to the 3.65), i wonder why).
Does it not mean that over time the voltage gap between the cells will drift more as there not hitting max voltage for the BMS to balance them?
Also when there discharged if there is a big difference then won't the lowest one be below minimum voltage?
Good question, at 3.5V per cell v diff will show up, so BMS will have a chance to balance cells. Didn't get about low voltage (BMS will disconnect pack if any cell drop below preset voltage)
i would rather use Active Balancer to help BMS on balancing task.
nice setting, nice test ...however I just don't get why the charging time with 3,45V compared to 3,65V is increasing (instead of getting less) (almost double) with same charging current ...why that?
probably because charger cannot push same amount of amps as at 3.65V.
Hi, I have 8 Pylontech LiFePO4 48v 50ah (2.4kWh) batteries with the charge voltage set at 53.3 volts in the inverter/charger settings. Assuming these are 15 cell batteries this gives a charge voltage of 3.55 volts per cell, would you consider this the optimum charge voltage for battery longevity verses charge times. This is the settings set by the system installer 3 years age, If I understood your excellent video correctly a lower cell charge voltage of say 3.50 volts takes longer but extends cell lifespan, i'd drop the cell voltage as for 80% of the year the battery is fully charged by midday and for the other 20% I top up the battery during the night on cheap rate grid power. Thanks in advance for any advice.
Hi, I'd double-check how many cells are there (15 or 16). Also based on my tests I would recommend lower voltage to 3,5V per cell. You'll still get the same charging speed and capacity, but the "safety" range will be a little bit more bigger.
@@SolarEngineering Hi thanks for your reply, I just checked, they are 15 cell batteries. So following your advice I should reduce the maximum charge voltage to 52.5 volts for added protection/safety of the modules, i've tried to prolong the battery lifespan by never discharging below 40% SOC, rarely below 60% SOC in daily use, am I helping doing this? There seem to be a consensus around this practice of limiting DOD to extend battery life so i'd be interested to have your take on this. Once again thank you for any views and information you provide.🙂👍👍👍
@@ambientfish1369 52.5 sounds right then. I think 40% SOC is too generous for LiFePo4, you could use 80% of it's capacity and it's considered as light use, also important C rating you charge and discharge (smaller rating = longer life).
(My statement about 80% is based on information I read on multiple resources, I didn't test it since it's taking years).
@@SolarEngineering Thank you bro for the replies I really appreciate your valuable time. I do try to restrict the draw from the modules, most of the day the house is using solar power direct from the panels, at night average draw from the battery is 220 w at circa 4-5 amps with an very occaisional 2000w draw of short duration for the oven (20 mins) max, I know it is worth being careful in how you utilise batteries and I want them to last as long as possible, thank you again you have been a big help🙂👍👍👍🏴
I've just set the charge voltage to 52.50 volts, thank you.
could you please provide the circuit used with arduino (and software) to monitor the load? I thank
Can you guide what should be the float voltage. If we have to set float voltage. 3.55 would be the bulk voltage
You don't need to float Lithium Iron Phosphate Batteries. Float voltage was from the days of Lead Acid Batteries that needed to be floated to prevent sulfation. Floating a LFP battery will shorten the lifespan of the battery as you are continuously running low level current (charging) into it.
Hello ,and thank you for your video, i have 105ah eve 8 cells,
So is 24v baterry, what is the best to get charge? I have set on my bms 3.6v per cell, and 28.8v total maximum charge. Is good? Or set at 3.55v?
Thank you
I'd go with 3.55V
What is the make and model of the battery discharger and where can I purchase it from
added link to the description, I've got it from Aliexpress
Hi, Good job!! I have a LiFePO4 in my motorhome. I need that it charge as soon as possible and that MPPT keeps the battery almost 100% all the time. Then I have: Bulk 14.2v. Absortion: 13.4v Re-bulk: 13.3v Do you think it is correct? Then When I have my motorhome parked It is plugged to 220v Then in that case I only need to maintain battery, so My paramters are 13.4v 13.00v rebulk 12.8v What do you think about that?
Does 3.65 volts mean 100% charge and 3.4 volts will charge the cell to 80%?
Or are 3.65, 3.5, or 3.4 volts the charging speed of the cell?
3.65 full charge, 3.45 ~80%. But LFP charge graph is pretty flat, so 3.45 can be ~70%-85%
i need help please,
i have 8 lifepo4 cells eve 105ah (my battery is 24v 105ah ) i have a bms , i want to charge to 3.55v per cell, is ok to change the settings only in bms from 3.65v to 3.55v and the sum high protect from 28.8v to 28.4v ?
thats correct? but my mppt charge controller is on 28.8v , i must change and the charge controller to 28.4v ? or just on bms and is ok?
please help, thank you very much
BMS is a 2nd line of control, MPPT should be 1st, so I'd do 28.4 on MPPT.
I have 2 lifePO4 12v 8Ah I bought the first of this month. I bought a charge you have to set type of battery number of cells, voltage, etc. I tried to see the charger work. When I hook either battery up and try to start the charge I get a cell warning on both and no charge. My other charger gives me a cell balance problem. What do you think? I just got one of the Miady 20ah batteries today. The charger is at my office so haven’t had a chance to try it with either charger.
Hi, I need more details: battery model, charger model. Do you connect battery balancing leads to the charger? If not then here is why the charger shows an error.
@@SolarEngineering the charger is a HiTec RDX1 Multicharger. I don’t see how to setup balancing for the battery since can’t get to the individual cells. I have an imax charger as well. I didn’t know at the time that Bioenno sold a charger that didn’t require the balancing would have bought it. But, now I hate to buy another charger. I’m using these batteries for portable Ham Radio operation.
Finally found the issue. Had to go into system settings and turn off balance charge.
But most LifePo4 chargers don't work with constant voltage , but they try to push as much current as possible until the voltage hit 3.xx volts per cell , So should take the same time to charge to 3.4 , 3.45 , 3.5 , 3.55 or may be a little shorter ?
But most LiFePo4 charge controllers, start in CC / Bulk mode but then switch to CV / Absorb mode.
Can I build a lifepo4 with different Internal resistance I have 32650 cells. some of the battery higher internal resistance
charger 20 amperes is it normal for battery 24v 100ah or is it very hight amperes
Damn! Would have loved to see this at 3.5 since we saw that massive charge time increase at 3.45. I would definitely not use 3.45v are itll take an insane amount of time to charge.
Possibly to use in car in very hot country?
At summer in closed car can be 90 celcius hot
LFP rated upto 50C.
90 will cause accelerated degradation.
maybe 3.5v is a good compromise?
19s 60.8v 30ah lfp battery charge which volts are best charger 67.2v/68.4v/69.35v and amps 6a/10a for electric vehicle
tanx for this video, i set my SCC at 28.2v (thats 3.525 per cell),,
glad it was helpful
Would be also nice to know the minimum voltage and if there is any sense to go below 2.6v
at 2.9 battery is fully drained, there may be just a few percent of capacity.
@@SolarEngineering I don’t go below 3v ever. The tiny bit of extra capacity is not worth the extra stress on the battery.
Why having a quality BMS is important.. You can set the cell charge rate to balance cells...
You've got cool stuff Dude!
A few more tests, may be you'll get more capacity 👍
I have 48v life po 4 cells I found that charging at 53.7v for 82-88% capacity and cut off voltage of 49v which is 3.065 is best long term cycle life.
what links do you have. you can provide a link
53.7 is 3.356 or 13.425 12v and 26.85. 3.065 is 12.26
@Meran - How do you KNOW that your theory "... BEST for long term cycle life ..." ?
@@MrSummitville its lithium so better not discharge to 0% nor always be at 100% high voltage
@@freetrailer4poor I actually lowered the charging voltage to 53.4
This has been confirmed multiple tests. No need to go very high or very low due to the steep curves after 90%
well, here is another one ;)
@Sanwizard - But we need to go to a high enough voltage to trigger BMS Cell Balancing ...
use Active Balancer to assist BMS
@@MrSummitville Use a Balancer that allows you to to set the start voltage and stop balance voltage.
what happens if you wait about 30 minutes between charging and discharging?
The voltage of the cells will drop to ~3.45V (if I understood your question correctly)
@@SolarEngineering yep. is that an important fact to highlight when comparing LFP charge graphs?
aren't most charge graphs based on resting voltage, not charge/discharge voltage?
I feel resting voltage isn't highlighted enough by many people.
Thanks
Good job
thanks
Yes Test Akb LiFePo4 👍🔋⚡
I'm going to tie 18s cells instead of 16s for 48v system. Then I think i can use around 60v to charge it and still get 90% of capacity
Cool😊
thanks!
So why > 3.45 V? At 3.65 V you gain 0.17 Ah more. That is < 1% of the capacity. If you stress your cells, they get dendrites or deposits. Even this video is 3 years old it has its important results. After viewing Andy & Co i drive my cells from 3.1V (0%) to 3.4V (100%). At these points the LFP-curves increases/decreases very fast. They leave the quasi-linear curve-pattern aka line. My guess: Obviously there is action. And action stresses everything.
Good test but your electronic load cutoff at 2.5V is not accurate as you are not sensing the batt voltage at the terminals. That tester has separate current and voltage terminals for you to sense the voltage at the batt terminals. Hope you use it next time.
Do you feel this causes tests to be inaccurate?
I think for this case it doesn't matter, I'm monitoring voltage directly from the cell using Arduino so all graphs are pretty accurate.
Load is just discharging cell (same condition for all 3 tests), maybe if I run other wires from cell to load, I'll get a few extra mA, but still, it's going to be the same mA for all 3 tests.
@@SolarEngineering I'm not arguing, just merely suggesting to use a feature that is made available for more AH/WH accuracy. We don't know how much AH or mAH is left in the cell because the cutoff happened earlier than 2.5V. In a 25AH cell with 5A discharge it may not be much but e.g. if you measure your 280AH cells at 20A then you can see a huge difference. And also you can measure an accurate WH with voltage sensing. Anyways your tests itself may be accurate as it's a comparison with the same load.
@@DSmartLife I see, thank you for the suggestion, appreceated.
My LifePO4 cells can not hold 3.35V discharging immediately to 3.3 level. Also not charging above 3.35 (53.6V) level. I think the DOD of my cells 80%. Anyone know reason for this?
are you sure that cells fully charged? Did you try to charge cells to 3.65V?
@@SolarEngineering When top balancing yes. I charged all cells to 3.65. But now cells won't charge after reaching 3.35V (53.6V)
hm, not sure why it's happening.
Хороший ролик, как называется ваше зарядное устройство?
Спасибо.
variable power bench supply, на амазоне большой выбор
i have 1 cell of 8 in a 24v pack 280ah cells that will not charge over 3.4 volts so i just made them all stop at 3.45 volts ,
Can you also do the test for low voltage please
do you mean measure capacity between ~3.0V and 2.5V ?
@@SolarEngineering Yes. Like you did in this test but for lower voltage cutoff. If you start at a fixed voltage (for example 3.45V) and then do discharge test from 3.45V to 2.75V, another discharge test from 3.45V to 3V and another from 3.45V to 3.25V and see how much energy you get out of the cell. Since discharging to 3.25V instead of 2.75V prolongs battery life but it would be interesting to know how much energy you can get if you cut under voltage sooner
@@hugodeandres1497 will add to my TODO list. Thanks
Hi SolarE Off Grid Garage is doing the same sort of testing!
thanks, will checkout.
my Batteries are 70 Ah each doesnt that change the results you have here?
going to be the same results for LFP for any capacity.
@@SolarEngineeringThank you that helps me tremendously
If you don't use the voltage sense leads on the DL24 your results will be a bit off, especially when discharging at over 1A since you can only use 12AWG in those terminals at most. There should be some level of consistency when you're using the same cell over and over set for the same discharge cut off but I'm sure there's variables influenced by the different charging voltages that could impact your result. I'd have to do some testing to see what I can pull from something like an 8Ah Headway with and without sense leads. I think I'll try that right now.
Since the max safe charging voltage of LiFeP04 is 4.20V there's really no need to put any safety headroom in place but I really do like 3.55V to 3.60V. Past that the voltage rises so fast that no balancer can handle an out of whack cell and a charge rate that is decently fast which can be very annoying.
There is no liturature out there stating 4.2 volts is safe for Lifep04.... that 18650 lithium style voltage territiory
@@johnd9763 wrong. You can even Google “safe max charging voltage lifepo4” and you’ll see right at the top 4.20V is listed. You can probably find some decade old literature on the internet for controllers and inverters that mentions voltages well above 3.70V. I found one a couple months ago that was likely from 2010-2012 that had the max voltage for a controller at 4.0V per cell. Wish I could remember the company it’s gotta be an old school one that’s likely still around like Morningstar
👍
Count amps in
Question remains: What is the impact on the lifetime of the battery?
Big enough for such a small decrease in available energy
I would also like to know that, to perform such test would take years :)
Main point is to keep cells away from 3.65V especially when many cells in series (16 for example).