Busting the 20%-80% SOC myth for LiFePO4 batteries.
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- เผยแพร่เมื่อ 22 ม.ค. 2025
- I'm reading many comments under my video where viewers state they only want to use their battery between 20-80% to prolong its life and reduce degradation. This widespread 'myth' may work well for Li-ion batteries but not for LiFePO4 cells. I explain and show you why it is (almost) impossible to use this SOC window with LFP batteries.
This is a bit of an introduction video about how far to charge and discharge LiFePO4. It is in preparation for a hole series of future videos about settings in solar charge controllers, inverters, BMSes and shunts.
As always, please leave your comments, explanations and additions below, so we can all learn and share our knowledge. Thank you if you have already.
Important video to watch and understand. Why charging speed matters: • Finding 20% and 80% SO...
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Because of your presentation style, my brain is absorbing the information without undue fracturing!
Thanks.
This is one of the most informative videos I've ever watched in regard to SOC on Li-Ion and LiFePO4 cells. Thank you!
Thanks a lot, glad it made sense and helped.
@@OffGridGarageAustralia look up carpen battery..70 yrs,,no charge..
@@OffGridGarageAustralia I been building off grid power systems for over ten years, I haven't ever kept up with lithium, I know lead acid, NiFe and nicad indepth, but I have a chance to win a 30kwh battery, and if I add 6 cells a 40kwh lithium battery for my self! This has helped a ton to get up to date, and an idea of what I need to design the build.
Going to be painful testing 24 individual cells! but worth it!, thanks to your videos I am selecting the JK BMS, I'll fabricate my own copper buss bars though!
@@Refertech101 Thanks for your feedback. All the best with your project. It will be great and very rewarding!
@@harrywalker968 da daaaa, vor sa distruga muzeul tehnic unde se afla...
Exactly the way I understood it after playing with LiFePo4 batteries for a few years. Most knowledgeable videos about these batteries.
Awesome analysis and comparison of the 2 chemistries Andy. Thanks for spending the time to bring a better understanding of the characteristic differences.
Perfect timing Andy, I'm finally setting up my own battery 2.0 and the Smart Shunt is part of that. So I'm keen for a deep dive into the settings.
Me too just in time. Perfect!
Next weekend i will install my first ☺️ 8x 280 with jk BMS and victron charger(800 watts panels)
@@camielkotte this is my exact setup. I have 2 pcs of 435w panels and 8pcs of 3.2v 280Ah Eve. I have a Victron MPPT 100/30 scc. Pls let me know how you go. I ask Andy whether the panels are enough to fill the battery for the day. I am planning to run fridge, freezer, washing machine and dryer for this setup.
@@noelbondad7423 hahaha. Funny. My pannels are 395. I have a 100-30 and a 75-15 SC. Panel lsc is 11. Thinking about a east-west setup and maybe more panels. But since we are only weekends and high summer at the cabin 2 panels should be enough. Only problem is a massive oak tree full of various kinds of birds right at the south ... So i oversized the battery.
What consumers i use will proof yhe choise of wh insyalled are enough. We want a microwave and a little oven for bread. Cant decide if it must be 24volt(thick cabling) or a 230volt (massive inverter).
The later Ovens use up to 3000watts during pre heat i believe where 24volts dont. Curious.
What kind is your sine inverter?
@@noelbondad7423 last weekend my brother helped install both pannels and i connected one. Today i replace the SC with the second panel inparalel. Must do some woodcrafting before placing the battery and tow the dead lead away.
Succes to you. Saw you channel, will look at it tonight.
@@camielkotte I have a 24v sine wave inverter of 2500 watts continuous and 5000 watts surge. At the moment my old setup is 24v system. 1 panel of 435w, Victron 100/30 Scc, 2pcs of 100Ah LIFEPO4 which I connected in series to make it to 24v. Now I want to UPGRADE my system with Eve 280Ah I mentioned above. I bought another 435w panel. These panels are Voc = 49.9volts. I am NOT SURE whether my Victron Scc can support it since its max is 100volt which is at the boundary of my 2 panels. Actually, my other issue is whether the 2pc- 435w panels can fill the battery for the day.
Wow, l learned so darn much from this video. This was one of the most informative videos I have watched about charging LifePO4 batteries. And I watch a lot. THanks so much for your great videos. You have a fan and will continue watching.
Thanks. I really need this and the type of info that you plan on posting. I had thought that I would not use a smart shunt just to save money, but now, I see the need for one to monitor the state of charge. It is interesting that counting electrons in the form of coulombs is really the most important measure in relation to SOC. Will be looking forward to your next few videos.
Thanks Bill. You can us the 'smart shunt' of the BMS as well but, but, but... it's not as reliable as the real smart shunt.
Exactly the information I was looking for - that's kind a scary ;) Unravel all these weird hardware settings would be a real interesting project. Thank you Andy!
Thank you so much for your contributions, the timing could not have been better for me because I’m putting my 280ah system together now so I’m looking forward to your future videos .
Looking forward to dive in to those settings. Your expertise make a lot of sense. Learning so much as always. Cheers my friend
I never thought I’d tell a block I’m excited but hey there’s a first time for everything ! I’m excited to see your results and findings Andy Mate. Mate 👍
Great to got you excited, Paul Hardie 😃
There will be more for you soon here. And thank you for being here!
I've seen li-ion based cells subdevided into 6 families. LiFePO4 is one of them, there are 3 types with mixes of Nickel, Manganese, Cobalt and Aluminium oxide s. These became popular for cars, power tools and 18650 cells. Most people think of these 3 types when mentioning li-ion. Would be better to refer to them as li-NMC , li-NCA to avoid confusion with LiFePO4.
Hi Andy, more great info as usual. As soon as the temperature in Melbourne rises over zero in Melbourne! I am going out to my van to reset my 200 amp LiFePO4 to use the full capacity (not just 80% to 20% ), THANK YOU!
Ok, secondly I am looking forward to the upcoming videos as mentioned, but one thing I would REALLY like you to explore/discuss is "Separate Port" BMS's.
There is a lot of poo pooing separate port BMS on the Net, this seems to stem from the lower charging rate available versus the output.
Now I agree that this can be a factor in a stationery system with lots of panels, which is why those systems should be a totally different discussion to RV systems.
Essentially you really do need a separate port BMS in an RV for obvious reasons, secondly the lower input is never likely to be an issue on an RV simply because you would be hard pushed to get enough solar on the roof to exceed the input valuation.
Personally I have a Daly 200 amp output by 50 amp input (dumb) BMS. I seems to be working fine for about two years, but I would really like to upgrade to a BMS that has Bluetooth and is fully configurable, but where to find such as beast?
I am aware that "hybrid" BMS's are apparently starting to appear, but I think it is still early has for them.
What I really want is something like the JK BMS with the internal balancing (nice), but with a separate charging port, any suggestions?
BTW, Daly has very bad communication skills, and don't make it clear you can order a BMS from them to order, that's how I got my 50 amp input model.
Also people should note, some distributors of Daly products (like Deligreen) are hopeless, they supplied me with an instruction set for connections for the BMS that was totally wrong and would have blow it up on connection.
P.S. They also lie through their teeth.
PPS,. currently everything is controlled by my Victron BMV712 networked to the Victron MPPT.
Great video, and looking forward to your settings series.
Coming soon!
You are an excellent scientist, and I very much appreciate your explanation of charge voltage at the atomic level!
Extremely valid information Andy. So we can extend the life span of our, kind of expensive batteries! While utilizing as much of our investment as possible!
Excellent and really knowledgeable video. Better than most others that really do not know much about lithium batteries.
The danger with keeping a near100% full LiFePO4 on a float voltage is that the (poor quality) charger can have an AC ripple with short spikes above 4.2volt even though the DC voltmeter says it is at 3.6volt constant float. Multiply values depending on your battery; 4s, 8s or 16s.
Those voltage spikes can cause metalic lithium plating on the electrode, that is permanent damage.
I charge my battery untill the first cell reaches 3.65v and then stop for the first cycle of the day. BMS calibrates this event as 100%, after calibration charging is resumed at 92% and stopped at 95%.
At midnight the flag for "calibration done" is reset so that it will charge again to 3.65v to recalibrate the next day.
The article "Practical Characteristics of Lithium Iron Phosphate Battery Cells" at Nordkyn design discusses the memory effect of not charging the cells to full (3.65v) on a regular basis. It starts building up a hump on the curve which gradually shifts to lower SOC, this means charging to only to 3.4v may reduce the usable capacity over time bacause it reaches 3.4v at a lower SOC.
In a truly off grid setup the typical daily cycle would maybe be 70% to 100% (defined as 3.65v) . Where I live there are infrequent events of consecutive rainy days where SOC drops below 10%.
I found the article, was very interesting. Regarding memory effect: it seems to take a long time for this to occur, and is generally reversible. The author states in the comments: "Memory effects don’t become permanent, they just become more difficult to overcome. [...] Performing a full recharge once or twice a year would appear to be quite enough in most cases."
@@ed-ey1yb This is very interesting to know. I made a note beside my HWT - which I drain and flush twice a year, as a self reminder to ensure the same for the battery bank.
WOW cheap charlie chargers with ripple and spikes - may explain the quite common sort of fire from these e scooters left on over night charge
2nd time watched it . skipped all easy informations those years you gave and i still find new ones.... . thanks.
This will be interesting. Looking forward to all the different opinions here and the facts as you present this.
Same, just started reading...
Oettinger! 😄👍🏻(I am wondering what it tells about me that this is the first topic I am commenting on on your channel, Andy. 🤣)
Seriously, I really enjoy the ride through your experiments and findings. Great stuff. Keep on going!
Thanks a lot for your first comment, Jürgen.
Great unboxing video!😀 Looking forward to the upcoming series on settings.
Coming soon!
One of your most valuable episode ever. Thank you so much for sharing your thoughts and knowledge. Very much appreciated! 🙏🙏
Thanks a lot for your ongoing support and donations, Lino.
@@OffGridGarageAustralia It’s the least I can do for you. Sometimes I am asking myself how much gear I would have destroyed (and money lost) if I would have generated all the knowledge you are sharing on my own. 😅
Merci pour tout ces judicieux conseils ANDY. Bonne continuation.👍
Thanks Andy - hilarious beginning as usual.😁
Very good topic- BTW I’ve received both my JK BMSs from China, one for my van (12v) and one for home garage (48v) already.
I’m impressed with the speed of delivery, obviously air freight!
My 400Ah Winston LiFePO4 cells for our caravan are now 6.5 years old, and have been charged usually to 3.45 volts during daily use, and then maintenance charged during storage (we don’t usually use the van in Summer) with a small solar panel (just around 50w, and only late afternoon sun) to a lower state, typically only 3.3v just to avoid any chance of going too low. However I know from experience that :
1. The actual state of charge can be quite low, as the Victron shunt (Bmv 700) gets waaay out of calibration over time, ie: exactly as you said. The ONLY way to recalibrate it is to fully charge the battery. I’ve seen it say the battery is at 100% during storage periods when it’s actually at probably closer to about 35- 40%.
2. My degradation is still absolutely minimal. I have capacity tested them last Summer (Feb 2022) by running an aircon and found the capacity at something significantly over 380Ah- I wasn’t game to go any lower as I didn’t have a BMS on the van, (but will have one soon!) and this means I would have had to watch individual cell voltages personally, just not worth the hassle.
Cheers and thanks again.
Thanks for sharing, Dave.
Just be careful with charging the 12V batteries with such small voltage, it can overcharge them and you're reaching a high SOC at 3.3V already and the charge controller keeps charging. It might be better to charge them to ~60% and turn of all loads and the charger. With 3% self discharging there should be now need for a trickle charge for quite a few months.
The Winston cells seem to be far higher quality and also better matched.
I've got your email as wee and will reply soon. Cheers.
@@OffGridGarageAustralia Thanks again Andy.
I certainly hear and understand what you’re saying about the longish periods in storage with 3.3v, however should have added that I feel I’m very safe as I very regularly use light loads such as charging my garden tools from the van’s inverter, and often even other items as well such as lights and even sometimes aircon if I am doing things in the van. (I have a 2.5 kW Panasonic split system in the van.)
The maintenance solar panel only receives mid to late afternoon sun- net result being that my actual state of charge usually goes down hill over time even though the Victron usually says 90- 100%. (As you know, that % SOC figure is useless when the battery hasn’t been at top of charge for a sync for a long while.)
For example, the last time we pulled the van out of it’s carport into full sun for a charge before using, I needed 250Ah going in to the battery to hit the top of charge, so the real SOC was probably something like 35-40%.
Weather permitting, we hope to use the van perhaps from the end of this week. I’m guessing that I’ll need to pump something like another 200Ah or so in to fill the battery, wild (educated ??) guess. Cheers
12v LiFePo4 im using settings in my SCC LVD at 12.6v and charging voltage at 14.2v i like that setting compared to default (Li) 11.5v LVD and 14.4v charging using a SRNE 40A SCC.. your channel is very informative thank you
Very interesting. I am looking for the next videos about this topic
This video was very emotional for me, so many tears Andy. Do you think you'll make a video reviewing your settings in your Charge Controller and Inverter? Would love to see that.
The video is coming soon, stay tuned... wipe of your tears first!
Very good video. Great detail on this subject. I have a 512wh Lifepo4 powerbank. I have set the upper charge limit to 90%.
I bought a Renogy 100W solar "kit" for my boat. It came with everything you need..panel, Z brackets, connectors, wiring, and a PWM 30A charge controller all for 129. Am charging a 100A Lifepo4 battery. (yes I immediately see I need more panels.) The charging problem I perceive is that the "Wanderer" PWM charge controller,set to Li. charges to over 14.2 volts! There are no user settings. Question I have is: What about using a Buck/Boost converter to regulate the current to 13.6 or somewhere in that range?
The flat charging/discharging curve of the LFP is addictive. Voltage sag was a mayor pain in the arsch with AGM, especially in freezing temps.
Voltagesag with AGMs suck but charging LFPs in freezing temps suck even more...
@@windsolarupnorth7084 Yep, built LFP batterybox with heating.
My car audio batteries get half-ish discharged and recharged several times a day. From 3.2 average to 3.6. The high amperage demand is what I think will kill them before anything else. When I enter in competitions the batteries get abused. My amp-clamp (dmm) has shown over 300 amps on one out of the four 1/0 cables feeding the amps. My home system goes from 2.85-3.48 and NEVER see over 120 amps. Itll outlast the car audio batteries BY FAAR. Excellent video Andy
Thanks for sharing. I always wondered why you guys don't use supercaps for this sort of usage. Or at least LTO cells...?
Finally I learned what happens when batteries charge and discharge. What anode snd cathod are. Such a great content. Love from Pakistan.
Looking forward to this series.
Thank you Andy, just in time my first 16 280Ah cells arrived this week. 🙂
Hey great!
As usual a very interesting video, Andy. I am looking forward to all the settings. Still strubbling with my absorption and float specs from the Victron RS450(wich I set close together).
Hope to see/hear you soon.....
Very soon, Victor, it is pretty much in production...
This is my first experience with you, having only just found the solar garage. I’m extremely interested as I plan to be building an off grid system in the near future & things have changed drastically since I was last fully off the grid. Looking forward to more 👍
Thank you and welcome to the channel. It's all here...
@@OffGridGarageAustralia Wow, you truely are a nice man. Thankyou. Can’t wait until we build my new system……Victron all the way 👍
I saw your eyes sparkle when you looked at those beer plaques! 👍 🍻
It's fun to learn together.
We love you to Andy!
Be safe all
Thanks 👍
ANDY, everything you just said makes perfect sense. LIfPO's were designed to be fully charged and fully discharged for a certain number of times before degradation sets in. But we all hope in the long run a little less heat when charging will lengthen the serviceable life of the pack. So for me, ill keep it down to 3.55 volts max charge voltage per cell, with a 4 hour float at 3.45 volts. Beer is on me!
A 4 hour float could overcharge them. These are not car batteries. having your BMS get every cell to 3.45 and balance would be better. he showed us where the curves are for these cells. 3.5 could even work but would stress the battery a bit more.
Only when you need speed charging (boat, RV, less sun hours) it is necessary to go above 3.45. Ones mileage will vary indeed.
For stationary and fair sun hours there is less need for higher voltages when charging...
So Andy told...
Thanks a lot for the SPAT 🍺, Bruce. Lower your float a bit and I'm happy with your settings. Thanks again for your support!
Verry clear explenation Andy, nice job as allways
Looking forward to see the results, i kind off winged it when i made my packs.
To make full use of the chargers capabilities i even went as far as to make 18S packs and charge them to 64V (max Victron voltage) this would be 3.55V per cell.
Dangerously close to 3.65 i guess but in a perfect world... i can never overcharge them.
In my installation you can clearly see that at 98%SOC the pack voltage is still only 60V (3.33V per cell) and after that it goes realy quickly, but to prevent cell runaway the batrium lowers the charging rate for the "top balalnce".
there are so many cool tools out there to manage your batteries, gonna be nice to see you play with them.
Batrium should send you a sample, they are "local" for you i guess...
Keep it up Andy, 40K subs soon!
Actually Andy, you are so spot on that I’ve got nothing else to say but…..thanks!
And... thank you, Karl!
Thanks Andy. Looking forward to the research study and testing. Have you or anyone found any real world research testing on the actual effects of over and under charging with LFP cells? I'll include references to some research papers, which suggest that it's thermal effects that largely contribute to substrate damage, and more a function of charging rate than absorption charge voltage, and that overcharge damage typically occurred at voltages above 3.6v. I could not find one study that suggested did several hundred charge cycles to 3.2v vs 3.6V that I seem to recall found no appreciable degradation until charged to over 4.2V to 4.8V. but if I do I'll add it to this post.
Here's some articles that are bit of a dive but give some insights into what is going on at the chemical level:
LFP overdischarge conflicting voltage limits - Thread starter Hans Kroeger Start date Jan 21, 2021
DIY Solar Power Forum - Nature Article number: 30248 (2016)
'The Degradation Behavior of LiFePO4/C Batteries during Long-Term Calendar Aging March 2021' -
Energies 2021, 14, 1732
"Because the 20% capacity fade and/or 100% internal resistance increase are considered
to be the EOL criterion which are widely accepted, almost all of the tests performed in
the aforementioned literature are carried out within this battery life span. There are few
studies on aging behavior outside this range. Thus, this paper conducted an accelerated
calendar aging test on a commercial lithium iron phosphate (LiFePO4) battery over at
least 27 months. By considering the storage temperature and SOC level as the stress
factors, an aging test matrix was designed such that the tested batteries were subjected to
the aging test under five different conditions. Based on the aging results, the impact of
storage temperature and SOC level on the long-term performance degradation behavior of
fifteen LiFePO4 battery cells was analyzed."
'Failure Investigation of LiFePO4Cells under Overcharge Conditions - 159(5):A678 - researchgate'
"The correlation of the changes of
cell skin temperature and voltage with cycle number suggest that an
internal shorting of the cell was developing with overcharging, which
eventually led to the failure. Taking a close look at the temperature
curve of each cycle (in the 10th cycle shown in Fig. 2c), the cell-skin
temperature slowly increased with time but began a sharp increase
at the end of the charge, indicating that the overcharge caused detri-
mental damage to the cell components. The same pattern repeated
with cycle number for each cycle, and the temperature continued to
increase until failure. The temperature increased with charging, then
reached the highest temperature at the end of the overcharge process
(33◦C at 5.28 V, peak 1), then decreased with discharging; however,
after the discharge plateau, the temperature increased again to another
peak at the end of the discharge (26◦C at 2.8 V peak 2). As for the tem-
perature at peak 1, the temperature increased with the cycle number at
a rate of 1.36◦C/cycle, reaching 45.8◦C when the battery failed. It was
also noted that in the last five cycles, the temperature increased with a
much higher rate, 2.54◦C/cycle than that of the first five cycles (only
0.02◦C/cycle). Compared with the temperature change at peak
Jack, did your text get cut off. Seems to end adruptly.
I am off-grid and charging at 13.60/floating at 13.50 (PV) based on your findings. Once I am confident my test system is functioning the way I expect, I will consider a little more investment. Thank you for your contribution to the DIY community...
Can i connect two of the same lifePO4 24v to get 48v ?
@@freddyswanepoel5640 of course you can (wired in series with appropriate sized conductor). Tie the positive terminal from one battery to the negative terminal on the other. Then tie the unconnected positive to a circuit breaker or disconnect switch (for safety) and from the breaker to a bus bar or fuse block to distribute power to your loads and the charger. Tie the unconnected negative to a shunt (for monitoring) or a bus bar for distribution to connected loads and the charger...
@@freddyswanepoel5640 you will want to verify, with the manufacturer, that the two batteries in question are identical as far as the type of cells, BMS, ...etc. which, if you bought them at the same time (or within a month apart), they should be fine. The reason I say this is because, what could happen is you may have a problem with balancing, where the charger will stop charging when it thinks the battery bank is fully charged (when in fact one is and one isn't). You'll want to fully charge each battery individually (then let them rest, and check voltage) prior to wiring them in series, in an attempt to avoid this potential problem...
You don't need to float LFP batteries, that was for preventing sulfation of lead acid batteries. Suggest you float 13.4v or lower if you have to use PV as a day time source of power.
@@s.mendez7160 thank you for your suggestion and yes, I am using PV to power things throughout the day, slowly working my way off-grid in the valley of the sun...
Small correction: LiFePO4 is also a lithium-ion battery. They all are. It would be better to distinguish by chemistry: Lithium Iron vs Lithium Nickel/Cobalt batteries. LiFePO4 really doesn't mind being charged to 100%. Keeping them at higher voltage (3.65V per cell) is more problematic since you can actually overcharge. Similarly, keeping them at 0% (2.5V) is generally not good, but anything over 2.5V (say, 3V which is pretty much still 0% state of charge) is fine. In other words, stay away from the very extremes and you're fine.
Thank you!
my observation of multiple laptop battery packs and brands is that their 100% charge requires cells to be above 4.2V. This has lead to many packs failing with just one or two bad cells; suggesting to me that these cells were over stressed. I'm imagining that something similar might happen with LiFePO4 cells driven to 3.65 or higher.
@@zaneenaz4962 "In the old days" we also pushed LiFePO4 to 4V as well. I agree that even 3.65V is pushing it, especially since there isn't much energy between 3.5V and 3.6V in the first place - at least for solar. If you do fast charging at high C rates, the voltage will rise faster and you might need to go to 3.6V or something to get the most out of the cell.If you can absorb for longer periods of time, even 3.45V like what Andy does is enough.
@@upnorthandpersonal What's the real difference between absorption @ 3.45V for longer and float @ 3.375V until the sun goes down? For example, I absorb @ 3.5V for an hour and float @ 3.375V until the sun goes down (~6 hours this time of year). Would the batteries benefit from changing to a 4 hour absorption @ 3.45V and float for @ 3.375V for 3 hours? Or are we just splitting hairs at this point?
@@bbrown_sc The key thing to know is that LiFePO4 wants to settle at a certain voltage, even after longer absorb stages. The important thing is to let it do so, which is why floating at high voltages is not a good idea, and 3.375 is often chosen below this settling value (in principle, you don't need float at all).
You can absorb for longer at 3.45 compared to 3.55 for example, but that's only valid if you have the time to let the battery absorb. If you want to charge faster because you don't have this luxury, you have to go to higher charge voltage.
In the end, for solar applications where we're talking low C rates and in principle can afford to charge slower, it doesn't matter. There is a lot of fine tuning one can do based on weather/seasons/etc. but one can easily go too far with this and spend way too much time tweaking parameters...
Great topic, exactly what I need, can't wait to watch next episodes
Thanks as a lot of good information is always learned from your videos. Keep them coming!
Thanks, will do!
another great video, very informative video with all of the key points I have been needing so far
Great, thank you!
Another great episode. Thanks so much!!
Andy, please explain calendar aging? Thumbs up and still subscribed!
You are a absolute star . From south africa
Ur the best for all of us newbyes in lithium battery world. Fantasik videos
Thank you very much!
In their product specifications, EVE themselves recommends the SOC window to be 10% - 90% for the LF304 and the LF280K. I always wondered how to do that with such a flat curve. Victron's charge defaults for LiFePo4 are 56.8v (3.55v) for absorption for an hour and 54v (3.375v) for float. Based on your recommendations I dropped the absorption voltage to 56v (3.5v) and left the float at 54v for my two LF304 based batteries. My batteries never drop below 50% SOC so I've never worried about the low end. I charge to 100% (56v) every day.
I found the Victron standard settings a bit too high. That may work for batteries which are many years old but not for new ones. If you can charge to 100% anyway every day, I probably would only go to 3.4V/cell as absorption and then set a time for that to like 4h or so... That is even softer and still fully charges them.
@@OffGridGarageAustralia if you have the capacity, go for de less degradation posible thanks Andy and Up North and Personal exelent information
Another great vid, I have often had similar thoughts with all ur testing video experiments, (hours and hours of them), why push the curves? Look forward to ur new coulomb counting methods and trickery. Cheers
Yes, it is far easier to stay withing the knees and use the rising/falling voltage as a trigger to stop charging/discharging.
Danke für das sehr informative Video. Du inspirierst mich meine "Balkonanlage" umzubauen. Victron Laderegler ist schon hier, Hankzor JK ist bestellt.
Wenn die Akkupreise wieder gegen Normal gehen werden auch neue (280ah) Akkus bestellt.
WENN die Preise wieder runtergehen, kaufe ich gleich so viele, das die gleich wieder steigen. Darauf warten wohl viele. Die Nachfrage ist einfach viel zu gross...
Can’t wait🧐 getting batteries sometime in June, so will be interested in the info. Love you too! (See I did watch to the end) 😊
Your informations are really good, as I just got my new LiFePo4 Bat -Pack! It helps me a lot! I will make 16S4P 280Ah Eve-cells
Well my new off-grid hunt camp power system goes active tomorrow. 520 watts of solar panels powering a 40 amp SCC to a 12v 200ah DIY Lifepo4 battery. I've been watching all of your videos along with Will's DIY solar forum and I'm still confused on what parameter settings I should use. You say charge to 3.4 (13.6) but what voltage should I use to start top balancing my battery? Guess I should rewatch some videos to see what I probably missed the first time. Really enjoy your videos and the time you spend finding and suggesting new or better possibilities for this battery chemistry. 🇺🇸☀️🍺
Hey, great setup and design. This should work well. For a rough start:
- 3.45V Absorption, Bulk or Boost voltage in your solar charge controller (different names for the same thing)
- 3.35V for Float (when the battery gets full)
- 3.45V Balancing start voltage (depends a bit on your BMS)
More details coming soon.
Another great video Andy.
Really looking forward to a more indepth look at the many unexplained parameters of bms's if that comes up as part if the new series.
Great stuff Andy, I look forward to the following experiments
The problem I have is that while the solar controllers are great for regulating the battery there seems to be no way to automatically divert any extra available current which for me is such a waste and I find that I can only go by voltage and have a diversion system that turns on by voltage but this does not tell me how much power is actually available so I can either take too much or too little power to my diverted load; any ideas you have how not to waste this potential power would be very helpful. Thanks
Thanks Jo. Yeah, that is a very difficult topic and problem. You can use some automation for that but as you said, it won't be perfect as the solar power may change and then you will use battery power. Basically you can only set a certain threshold to turn on a water heater when you hit absorption and then turn it off again if the battery goes under 95%SOC.
This is something we will explore as part of the automation I have planned for my system.
Andy, thanks for this fantastic video. Incredibly well done.
Hey Andy - A test idea for you: Variable discharge rate curves.
Many times we have seen you show us the flat voltage curve of LiFePO4 when discharging (or charging) between 90% and 10% state of charge and with the knees at each end of the SOC.
Most of these show the curve when tested with a constant discharge rate.
I was wondering however what the discharge voltage curve looked like if you programmed a variable rate of discharge, say cycling between 0.1C and 1C for 5-minutes at a time, or some other variable load profile. How much "wobble" would the voltage display when a battery is being discharge with variable rates? You have a battery tester which can be programmed to run such a test I believe.
It seems to me that variable rate of discharge would be a more realistic test of the demands placed on many batteries.
Thanks and keep up the good work.
Thanks Alex. I have tried that in some experiment already and the result was... there was no difference. The think is the Peukert factor for lithium cells is almost 1 so it does no matter with which current we charge or discharge the cells. The curves will look almost identical.
I can do the test with my tester and show you in a future video, no problem.
Thanks for your suggestion.
I made a 100ah 12v lifepo4. I added cheap voltmeter-usb combo to the pack. Digital voltmeter reads 14.9v. I recently bought a smart sensor which reads 13.65v at rest. Been running battery for two seasons no snd.they are amazing.
Finally gonna be some videos on how to set up the bms parameters. I've contacted overkill about doing some videos on custom bms settings. They said it was a good idea but haven't seen anything yet.
I have 6 280AH strings of batteries with 6 over kill 48volt bms and haven't used my batteries at all because I'm trying to figure out how to navigate the xiaxiang app. I want to do the max amount safely and with longevity. Also what is the charge rate? What about the float? Obsorb? Like to see how to do the bms settings. I have trouble naming all 6. I got 1 named but the app refused to let me name the other 5.
I know, there are a lot of parameters and settings. And they are more and les connected to each other, so it's really time to kick of this series! I was so confused myself and could not find answers either. Every forum, every website a different answer... So I did all the testing myself.
I bought a server rack 48V battery, and its BMS talks to the inverter. I am still experimenting with the charge parameter settings. With this communication (battery & inverter both EG4), do I really need a shunt?
Outstanding discussion well backed up by theory and practice.
I just wish more folks subscribed to that formula for success.
Thanks a lot, appreciate you feedback!
I appreciate the graphs showing the difference between Lion and LiPO4.
Unfortunately, my Bluetti solar generator was not charging its LiPO4 batteries properly. They overheated at 100%, because they bulk charged to almost 99%. Its 30C here, but no excuse to not being able to function properly when I have a BIG fan blowing on it!
I told customer service, but no one understood my technical question to update the firmware. I now know where their charge rate was improper. Returned my EB3A, since it could never achieve proper life expectancy!
Bulk charging to 99% is not a bad thing with LiFePO4 and usually works well. Once the voltage rises to over 3.45V, the cells are 99%+ charged anyway.
Appreciate the explanation and frankly was quite surprised. My Lifepo4 battery manufacturer wants me to charge it with 14,6V only. I guess they want to sell me new batteries soon? :)
It depends. If it is a 12V battery with built-in BMS and a very small balance current for example, this would be the only chance for them to balance this pack at a higher voltage. I would not bother and just stop at 13.8V and let it absorb there. It will still be 100% full
@@OffGridGarageAustralia Yeah. Now I have noticed that my Ultimatron 200Ah batteries work nicely with 13.6V (Epever 10420), but Wulills 200Ah batteries need 14.4V (with Victron charger) to fill them up.
T1 Terry said this for Winston cells about 12 years ago. These cells were like calb ones. Many of his followers are still running these cells. I used his secret settings on my old pwn plasmatronics controller and its so close to what you are saying. 13.65 v was the charging voltage for 4 cells
Hi from Sweden, I love your videos! 😀
Hi, I have an 18v electric saw with a push button that I can see Soc it shows less when the saw is running so I assume that is the more correct measurement.
Thank you for the info and knowledge sharing! Keep it up!
very good, you got a new subscriber here in QLD 👍🏽
I need help. I’ve got a 110ah leisure lithium battery, charged by dc-dc charger, which runs a 12 volt fridge, the BMS shuts off power at 10.5 volts, which means the fridge is also off for a few hours before sunrise. Do I need more batteries?
Andy,
If I may ask.... What is the calendar shelf life of lithium cells?
I am currently using grade B CALB cells which are 10 years old.... Still going strong at 90% capacity, 100% off-grid with daily capacity discharge from 100% -30% level. I just keep wondering does it mean there's a day I may just wake up to find the storage bank is 40% or less ?
Then why should I not just consume all my capacity while still alive ? I can imagine .... I might take another 15yrs to get to 80% capacity.
I don’t think anyone yet knows the calendar life of these if looked after properly. Suffice to say: it’s good.
Calendar life only means that batteries degrade from age if they are used or not. It does not mean they will be dead at a certain time or date, but still lose a tiny bit of capacity every single day regardless how and if you sue them. If yours are 10 years old and still have 90% capacity, that is great
@@OffGridGarageAustralia
I am in my 40s, I guess they will be still alive when am gone.....I appreciate your educative videos which will help us to extend lives of these cells for quite so many years to come.
I always remember the argument of Bulk Voltage being same as Float Voltage. My cells get full by mid-day, I keep using the PV power without cycling my cells for the reminder of the day. This makes me to cycle the battery bank for less than 1 cycle per day.....This is very helpful insight I see many of solar users do not know...
I really appreciate your work..
@@innocentusangira789 thank you. It depends on the exact settings in your charge controller if bulk should be the same as absorption and also the devices you're using. Watch the upcoming videos about the settings to learn more. It will be interesting.
Fantastic explanation Andy.
Correct me if I’m wrong Andy but most BMS do not start passive balancing until 3.5 V so charging to 3.4 V Will mean the BMS won’t balance the cells.
The way that I look at batteries is they are a consumable item that is going to wear out over time i.e. lose capacity slowly no matter what you do you may prolong the life by only months maybe a year , it really comes down to how hard you cycle the batteries from my experience if the batteries are cycled hard you get an average of about three years out of the batteries where you have now only 80% of your original capacity regardless of how you try to look after the batteries, Like you said it depends on the C rating of your discharge so the more capacity you have the longer your batteries are going to last.
The most problems I’ve seen with lithium batteries in the caravan and camping style of things is generally cell in balance over time reducing the overall capacity. I really like the effort you’re going to and I realise how much time you put into these videos thank you for busting some of the myths out there.
Thanks a lot Phil, great comment.
With LiFePO4 chemistry, it makes no sense to balance below 3.4V. But stopping charging at 3.45V and balancing at 3.5V makes all the sense. The balancer will only start cutting off the voltage of each cell which dares to go over 3.5V! If the balancer does not start balancing, that's great because there is nothing to balance.
Yes, if you cycle them hard it will burn them out far quicker, absolutely. Because many of us have invested a lot of money in these batteries, we try to understand how to prolong battery life and keep the usable as long as possible.
The videos are taking a long time to make, edit, upload, describe, thumbnail and reading the comments afterwards. Thanks for appreciating that!
To add even more uncertainty to the SOC, is charge rate. When charging to 80%, the voltage will vary depending on how many Amps you are charging at.
The only good thing about a lithium cell is they are lightweight. All forms of battery cells are garbage. Our bodies are the best energy devices ever created due to the small amount of resources needed to do a large amount of work. An electric generator is great , the only problem is we need something portable that is good enough to power it. Fuel combustion is still our best bet. I can make my own fuel and get a lot of energy out of it.
Andy, I have always agreed with you regarding not charging to 100% max. Something to also consider is how the battery is being used. I have 2P4S 560AH(LF280 cells) battery on my sailboat. The battery can be charged 3 ways: [1] shore powered charger(5A to 65A), [1] solar(350W), and via alternator(120A). Since I have been mainly day or over-night sail, I rarely charge via solar(keep flexible panels safely stored) or alternator because of the large capacity compared to my needs. When I am not sailing, the vessel is connected to shore power. I have the charger set for 45A boost charge to 14V(3.5V average cell). It stops charging until the battery hits a "boost return voltage" of 13V. This take about 3 days with loads mainly being for my refrigerator, computer, and networking. I could set the return voltage lower but I want to be able to randomly show up and go sailing with still plenty of capacity. I have a JDB SP04S034 200A BMS which has both bluetooth and RS485 communications. I readout the RS485 with a raspberry pi via a simple python program which creates plots for 2hours, 48hrs, and 7days windows. I can connect to the sailboat's raspi remotely via vnc to view the monitoring plots. It is interesting to note the cell deltas increase and then decrease during discharge cycle at what I call a "mini-nee", which is the at the 3.3V to 3.2V cell voltage drop. I wish I could send you some plots. The delta raises up only about 20 mV but then drops back down is a rather symmetric fashion. My guess is some change in a phase transitions.
Why do you keep bothering yourself with shore power? while you could just fix a 2pcs of 500w panel and forget?
Alternator charging should also work very well on bad days
@@innocentusangira789 Why? Because: I have a big boat and when it is in its slip, [1] shore power is free and my automatic transfer switch will automatically switch the AC loads from the inverter with no interruptions, [2] I can run my boat's 16,500 BTU air conditioner(A/C) without concern(through the battery inverter it would draw 100A), [3] I have flexible solar panels which I can easily utilize for cruising beyond day trips and are safely stored greatly reducing degradation which is greater for flexible panels, [4] reduced battery cycling and different operational demands( I want solar to keep the battery near full so that at sunset to sunrise, I have maximum power availability(and possible use my A/C for several hours allowing for over night cruising during the hot & humid Florida summer season), [5] ...
@@dreupen how much power do you consume in a day ?
The storage you have can only be filled with the few panels and yet... You will keep recharging even if you are in deep sea parked
Yep, so on a boat it's a bit of a different situation and you want to charge your battery with anything you have as fast as possible. Different to our solar stationary setup. I agree, in this case it makes totally sense to charge the 3.55V or even 3.6V as fast as possible so you're ready for your next trip. You certainly don't want to leave a port with only a half charged battery.
@@innocentusangira789 The issue with boats is space, and going from a 300 watt to 500watt when the panel is mounted horizontal is not worth the investment or the time to install.
Love the intro Andy please keep in mind some people are very impatient nowadays😁 and might want to know the optimal speed for charging without excessive degradation. While binge watching your videos everyone a jem And wealth of knowledge, I noticed, This is a topic you rarely discuss Sometimes barely glossing over it.😂 like Low voltage, high amps. And why some "popular" battery manufacturers push 14.4 to 14.6
Thank you. I hope to make this clearer when we go through the settings of solar charge controllers soon. This should clear things up.
Hello can I ask you if the positive connection it’s in contact with battery case ?
Correct, the positive of the battery is the outside case.
@@OffGridGarageAustralia thank you
Another thing to consider might be the swelling that occurs while charging and discharging. I don't know how much this physical movement of the cells contributes to degradation, but the swelling on my cells tends to occur more at above 3.35V/cell (26.8/8 cells).
I also consider how long my battery will play my stereo at full volume and whether or not it's long enough to make me happy. Will my hearing be degraded before I need to replace my battery? Time will tell the result of that experiment. You might want to consider/research adding closed captioning to your videos in the long term😁
Thanks for your input. I have enjoyed your videos 👍
The swelling is minimal and often cannot be measured. I'm using my cells uncompressed with some minimal space in between and had some swelling after 1.5 years of using them like this, so the cells actually touched in certain areas.
So you either compress with recommended 300kgf, leave some space between the cells or use flexible busbars, so cells can move without putting force on the terminals.
I like you stereo experiment. That is really outstanding😂
Bonjour donc au finale c'est normale que les cellules gonfle ??
Great video Andy, thanks very much. 🇬🇧
Very interesting!
Great explanation.
Andy, have plotted any charge/discharge curves for some of the common 100Ah 12.8V LFP's by Li-Time or Power Qween? Their chargers are CC/CV 14.6V which is not necessary except for cell balancing. Seeing a charge curve would be helpful for setting up a Solar Charge Controller specific to those batteries. Thank you for your awesome productions.
What is the maximum number or range of battery cycles for the lithium ion ?(Under standard or feasible conditions)
Looking forward to this Andy.
the bench is clean and free - looks like new project on the horizon
but that was just at the beginning of the video before you unpacked that lot of stuff.
Hi. I found your video very informative.
I run my Escooter 48v 20aH (960wH)
Voltage is basically my 'fuel gauge'. :)
Calculating in my head (and after a few test runs), I worked out that 47v (resting voltage) is my 50% mark (or turn around time!)
About 50Km round trip....
I'm thinking about installing a 48v 100aH battery for a long distance endurance run (project w solar)
Cheers von Australien 👍
L.E > Ideally i would require a 48v small petrol generator, say 850w which I can recharge on the fly, so to speak. I've not yet looked into availability....
However, with 100Ah i sink I would get around 250 Km out of it.
(5Kw x .30 cents = $1.50 to 'fill er up' on AC charger..) 😅
I could use some help. Running 200watt solar on a camper for the 12v fridge. have it connected to 30amp pwm controller then to the lifepo4 battery. from there I go to a 25a breaker for what breakers do and to isolate the lifepo4 from the lead system when in use (the truck alternator/shore power). Then I put another pwm controller set for 13volts going to the lead battery. So the solar charges the lifepo4 then the lifepo4 charges the lead. The lifepo4 does most of the lifting charging and discharging. Am I off my rocker or is this viable. only on the second test right now. First time I was pumping to much to the lead so backed it down a bit.
That won't work. You can have only one controller connected to your panel.
So, solar panel - PWM controller -LiFePO4 battery.
If you want to charge the 12V battery as well from this system, you would need a DC-DC charger. The takes energy from the LiFePO4 and charges the 12V lead acid battery. Renogy makes them for example.
@@OffGridGarageAustralia Thanks I'll look into DC-DC charger. I was thinking the second pwm would work as a dc-dc charger. This last test looks promising but did not want to go to far and find what the breaking point is and damage the battery.
@@swamprat9018 nah, the voltage difference is not there to charge one 12V battery from another 12V battery. The DC-DC charger has a boost converter to raise the voltage to 16-18V. PWM solar chargers cannot do that.
@@OffGridGarageAustralia I only have a 200 watt solar panel rated for 17.?? volts going to the first battery. I've only seen it get up to 11v. in daylight so far. So I don't even have enough solar to charge the lithium battery with the provided PWM set for lithium settings. This is making me into the un happy camper group. LOL Thank You for sharing your knowledge and time.
@@swamprat9018 disconnect the solar panel from the battery and measure the voltage without any load. It should show the 17V. It's normal once it is connected to the battery, that the voltage will go down.
Hi Andy. Great Idea! Please include in to the scope also solar charge controller setings. E.g. where to set a voltage of 3,4? Is this in SCC or BMS etc. Another topic is why not to read state of charge from BMS using CANBUS vs using SmartShunt? Maybe this is clear when you are at battery version 2 or 3, but for those who are at version 1.2 there are a more questions than answers
Yeah, we will go through all the settings soon...
I'm not a fan of communication between BMS and solar charger of inverter. It brings no benefits in my experience and only ads further complexity. It's not necessary.
Great video again good insight into SOC. Have you looked at or tried a Batrium BMS its an Australian company and from my limited research they look great but the price tag is a little high but they do everything you need bar getting another beer from the fridge. Keep up the good work.
Thanks a lot Keith.
I'm in contact with Batrium but felt it's a bit too much. I rather wanted exploring 'normal' BMSes and their flaws, helping more people out and sharing my experience.
I'm sure the Batrium will just work fine without problems. But it's like making videos about Tesla's Supercharging: it just works and is boring to watch.
Hi according to you what is the best charging voltage of 16pcs connected in series livepo4 ? 😊
So.... The ideal voltages to charge the lifepo4 is 13,6 and don't discharge more than 12,4 volts. If i conect in parallel with some AGM batteryes...will be fine like that? 13,6 and 12,4. I will use bouth of them...and charge and discharge corectly. I undestand it well? But in 24 / 48 sistems?
I would not recommend charging different chemistries in parallel. There will always be limitations.
but if you don't pass the maximum voltage.... What could hapened?
Hi, got a few questions the lifepo4 battery is showing 3.2V on the sticker so why r we charging to 3.45V. I am getting my new batteries I am not using a smart chant I am using a daly bms. Can you tell me the best figures I should keep my batteries. It'd a 320Ah batteries 16cells. The supplier only gave a few data n that don't have any figures as highest charge n how far I should discharge etc. Any help would be great.
Hello Pulith. I have linked a few videos about what you should know about LiFePO4 in the video description and also at the end of the video.
3.2V is just the nominal voltage of the cell but we charge it higher to 3.45V-3.65V. This is similar to 12V batteries which get charged to 14V.
@@OffGridGarageAustralia thanks for the reply. I will check. If I get stuck I shall ask you. I am in srilanka so any help you would give would be highly appreciated. Thanks in advance. I learned alot watching your videos.
Ich liebe es, wenn du tust, was du eben tust..🤣🤣
Andi hör bitte niemals damit auf..
Der Anfang des Videos ist so bisl wie Weihnachten, beim zuschauen was die anderen so auspacken..🤔
Und dann bringst wieder ein grübeln in die meisten Gesichter..
Mach bitte weiter und weiter und weiter..
Wozu zum Geier brauchst du ne Bilgepumpe ??? 🤓
Vielleicht zum Bilge pumpen? 😁
Danke Dir vielmals. Die Pumpe brauche ich fuers Bierbrauen! Habe den Oettinger server gehackt und das geheime Rezept gefunden...
@@OffGridGarageAustralia 🤣🤣🤣🤣🤣🤣
Andy your research is so helpful
No matter how many times I watch your videos I always reference them time to time for help . Helped me get off the crooked grid People wish they could be as cool as us off-grid family ❕✌🏼
Thanks a ton buddy 👍🏼❗️❗️❗️🇺🇸🌞
Love you and your work here
Sir, after the number of rated charge cycles (4000 to 8000 they say) of my 12v Ampere Time 300 ah LiFePo4 can I safely keep using it? Like once the capacity begins dropping below 250 ah? Is there any danger?