LiFePo4 and Absorption. What I learned from my previous mistakes...

So this is a bit of a long story. I had some problems re-charging the battery after the last discharge. When it got fuller, some of the cells peaked and I had to manually discharge them. The more cells peaked, the more I struggled to keep the situation under control. At some point I turned charging off as I could not handle it any more. I'm not sure why the cells were so mis-balanced from the initial top balancing...

Well, I found another method online how to balance the cells without disassembling the whole pack again. So, that's what I did the whole week long. It took a while and I learned a lot about how these cells work and behave. It is all about the voltage and current. I was so wrong by just looking at the voltage...

Will the battery work after this crazy balancing procedure?

New XiaoXiang App:

Please subscribe and join me on my journey of the Off-Grid Garage!

[rzlchoq]

Great work! Appreciate it. Thank you for the opportunity to study together! Best wishes from Ukraine 🇺🇦

[davidgraf]

Thank you for teaching us as you learn these things yourself.
I have learned so much from your videos! There is so much to learn and you are so good at explaining the key points from your testing. Your channel is the best I have seen to truly make the complicated simple to grasp and you do it with great music and personality!!

[bobfoulke]

Thanks so much!! I have learned more from this and your next video than I have learned from tens of hours of solar/charger/battery videos over the last year or so

[Chicago]

Hey! Tried this and it works! My batteries have a complex installation and I really didn't want to take them out of place for servicing. I achieved balanced cells merely by lowering the overvoltage cutoff to 3.45v as you suggested and voila! Thanks!

[dashbrj]

Always a good day when I see a video from @Off-Grid Garage :)

[sergioduarte]

Hi Andy. I will give you my opinion. I made a battery with 22 LiFePo4 cells and installed without BMS on a scooter. 2 years after almost daily use I don't see any imbalance. After much reading and watching videos of experts, I opted for the technique of bottom balancing instead of top balancing. The explanation is simple. All cells have a common minimum, but not all can have the same maximum.

I unloaded cell by cell until its minimum tension and left it to rest for 2 days (the tension will naturally rise a little, being necessary to repeat). With all the cells equal at the minimum voltage, I connected them in series and connected the charger until it reached 80% of the maximum capacity. It is my safety margin and I guarantee that all cells are able to balance themselves at this voltage. LiFePo4 chemistry is very stable. It's just my opinion. Good job Andy.

[phillipchen]

I appreciate your efforts. we are all learning together.

[jeffma]

Dear Andy, love your humor and most practical demo of solar system building.
Just went back to watch your first episode from very beginning. Love it and enjoy it.👍

[catchfrubert]

Hey, Andy! Great video! The problems that are the most difficult are also the ones that will teach you the most. You already made great progress and learned a lot. I have no doubt you will find the settings for the charge controller and bms that work for what you want. Good luck my friend.

[trevilights]

Great Video. I've been experimenting with a Growatt 3000K 24v 8S 3.2 cells. And It is very confusing to get all the parameters rights. Your video has clear many questions regarding CC/CV, voltages and amps. I am still playing around but I think I have found a sweet spot for my setup. Thank you very much for sharing.

[davebutler]

Excellent detective work there...
It's even harder to build an understanding when you have experience that needs to be forgotten because it no longer applies.

It would be interesting to see what the settled voltages of each cell were, after you carefully saturated each one.

Perhaps they each have a different saturation voltage... This would explain why the voltage based balancers can cause trouble!

[caribecastaway]

Very insightful, excellent material to ponder. You have hit on an issue that I have been thinking about too. The longevity of the the batteries is greatly diminished by charging to 100%. a combination of voltage and current monitoring must be the answer. The tolerances are so tight as you point out it's so difficult to get it just right. Keep up the good work. Perhaps keep a log of the batteries that are always the highest and lowest to see if their performance deteriorates faster than the others. Keep testing to find the sweet spot! Thanks for your video

[BenMitro]

Great insights there. Thanks for sharing with us! You learn when you jump in the deep end - if you were mucking around with cheaper, lower capacity or fewer cells, you wouldn't worry about these subtleties as much.

[cowboymcq]

No matter how many times I watch your videos I always seem to go back and learn something new YOUR videos never get old my friend
THANKS ALOT 👍🏼🇺🇸❕❕❕

[chrislant]

You rotten sod rubbing it in about your lovely weather and how we are freezing and your going in the pool to cool down !
Great episode as always. Lovely to see your frog at the end.... kept thinking of them when I saw your green battery indicator on your phone. Learnt a lot from your channel. Thanks

[stevenbraun]

Just watched this video. Experiencing the same problem on my golf cart project. I have a 135A 14s LiNMC battery with a JK BMS, a 300W solar panel roof, a Victron 100 20 MPPT, and a Victron 712.
Massive amounts of sunshine here in So. California. Trying to keep the solar power system from triggering the BMS. This video has gone along way to help me understand the MPPT settings. Thanks...

[MrSchnickel]

hi ANDY there are many teachers in this world, but very view can explain a process that everybody can understand it. u are one of the view exceptions to make ur presentation clear. it was the first time i see the total picture of charging a lifepo4 battery. thank u great job. i am the German guy in Texas and just started up my 30 kw system with a 8 kw solar system. i am using a SOL ARK grid tie inverter that can start a back up generator in case the grid goes down. i will make a you-tube movie the next few month and will send the link to you.
again thanks for all the patience and smarts you have. viel glück Jan

[Sirslayer_X]

You been my teacher and I've learned a lot from you.. I'm using sealed wet cell and I know If I took my batteries and disconnect from my system, the solar power of 1000 watts would just take over and maintain my 12 volt / 1000 watts requirement. I really think you very close on solving this.. I live in sunny southern California and my generation has been excellent. If you can master using your batteries banks with the solar system and normal load usages at the same time, then I will upgrade to lithium lifepo4. Thank you for teaching us !!

[Dirt-Diggler]

I think this was one of the best episodes for learning and conecting things in my brain !
when i test lead acid batterys i have this system, i charge and leave on float for 3 days to let all the energy absorb, i stop the charge then i test the voltage after an hour and then after 24 hours another voltage test and a 50A load test and then i choose the batterys closest to each other to put in a battery bank for solar, it's just the way i do things after years of charging used batterys and resurecting them for solar powerbank use but after watching this vid it clicked, somone else has similar thoughts ! differant chemistry i know but cool to see a similar thought process in somone elses head !I really really enjoyed that one, i love learning alongside you ! keep it up :)

[JonCumming]

you're the best ! I literally want to go to Australia specifically to hangout with you 😊. I enjoy learning with you and appreciate your fun attitude to figuring out problems 👍
By the way I am in the middle of this exact issue you encountered here . Just did a single cell to 3.5v taper to < 0.1amp for each cell..I then paralled em and did the same thing.
Waiting for some load testing equipment to re-test. Fingers crossed