I purchased
4PCS LiitoKala 3.2V 280Ah lifepo4 battery DIY 12V 280AH rechargeable battery pack for E-scooter RV Solar Energy storage system
x2
from Ali Express. Took over 2 months for them to arrive. Configured them in a 12V 4s 2p arrangement with a Daly BMS and am using a Renogy 100 charge controller. The setup seemed to work but then the cells began to physically swell (even thought their individual voltage never exceeded 3.4 V). Swelling cause the busbar to pop loose (see photo). Are these cells fried???? If so were they faulty or did I do something really wrong?
View attachment 58077
OK lets investigate
Here is a (not so small) questionnaire that is a base to analyse the battery failure and to point out potential problems:
- Cell compression, method? In your case cells not compressed. Not ideal but can work. Cells breathe so at 100% SoC bloat a bit and then when SoC goes down so is the bloating.
- Cells setup? In your case you did a 2p4s setup (2 parallel and then 4 times this serial). Not ideal but can work. BMS only saw the average V of two cells.
- Did you do a proper top balance of the cells ? What were your procedures, how did you do it ?
- Copper busbars on alu terminals. That is not ideal at all. Did you use noalox or carbon grease ? Terminals polished ?
- What was charging the battery ? MPPT or PWM solar charge controller or an utility charger? Size, Type, connected solar panels number, Voc, Vmppt, Amppt ? Charging settings (bulk V, absorption V, float V, max charging current) ?
- What was discharging the battery ? Inverter (size, type?), direct load ? Max discharging current/watt estimate ?
- Cells electric separation? Standing on a non conductive base? Non conductive separator between the cells ?
- Cells placement? Shed, garage, inside/outside? On the ground, on shelves, ... ? How protected from fauna (rodents, bugs) and flora ?
- Ambient temperature? Cells and busbars temperature in high load/charge (hand test not warm is OK) ? Any extra cooling like fans ?
- Humidity? Pipes near the battery, MPPT, inverter? Possible water, steam or condensation in the area?
- Cable size/type to BMS and after that? Fuse after BMS, size?
- Usage of the battery? Constantly charging, lot of time on max charge (SoC >95%)? Lot of time in minimal charge (SoC<10%)?
- Where the battery floated? So SoC >95% and float V > 3,4-3,45V/cell ?
- BMS is Daly. Which type, how many A? BMS still working ? Cell Volts in Daly the same as by measured with a multimeter?
- schematic diagram of your system would be appreciated (maybe some pics from it and from battery).
If you give the answer to this questions maybe ... maybe we can point out things that could cause your battery to fail/bloat.
So for the next battery you build you could change it and enjoy your battery for a long time