Hey guys.
I have a 12S5P using 30Q Batteries. I didn’t use my Mountainboard much this year so I had it stored for quite some time. I wanted to check the battery pack and bring it to a storage voltage of around 3,6V per Cell because winter is coming soon but when connecting to the BMS I saw a drift of 0,3V on Battery Pair #12.
I then charged the pack up and activated static balancing and could get it to around 0,2V as of now - so it might take several discharging / charging cycles until it will match again.
Any ideas how to identify dead batteries or would you just replace the whole row ?
The Pack is quite new and I checked continuity of the parallel pairs and everything seems fine.
So I think one dead battery might drag down the other ones so thats why I have the difference in voltage.
Since my battery pack is quite glued together so safety reasons it will be a little pain to disassemble everything.
while off, check the balance lead for group 12, yank on it, if its solid continue to charge to full
If group 12 drops voltage after full charge or it can’t get to 4.2 then there’s atleast 1 bad cell, youll need to remove the Pgroup and break it down to determine which cell
The balance wire and all the other wires (connecting the P and S groups) are properly in place.
I will see if I can get it up to 4,2 with a couple of charge / discharge cycles and report back.
Somehow the balancing functions seems so slow and half a$$ed to be quite honest.
The balancing only seems to discharge the higher voltage very slowly but it does not distribute the charge really - not sure if this is supposed to be that way ? I have a smart bms from aliexpress
Unless you don’t have money, always change the whole series if it goes bad. I seeyou kept your battery stored at max charge which is not good and that is most likely why the series got worse. BMS balancing does nothing pretty much. If you wanna balance out 0.3v, it will take around 100-120 hours of constatnt static balancing for the BMS… Get a lipo charger from aliexpress, that way you can balance out the one series through the balancning cable in a few hours. 0.3v after a longer period of time might not be that bad… Just charge it back up to the level of others and you will have less capacity on that series, but you should have most of your capacity is my guess.
So after some days of balancing and doing some charge / discharge cycles I think I can only get to around 0,1-0,13V at best.
Since Winter is coming I will leave the Dead pair in the pack at the moment (worst thing that could happen is that the whole parallel row - 5 cells - will die completely but I plan on replacing them after the winter time).
What is a good storage Voltage for 30Q Batteries so I can discharge to that value ?
Also would you keep static balancing on over winter or are there risks ?
If the defect cell is discharging itself it could lead to a discharge of the hole pack, so keep an eye on it over the winter.
Also the bt module will use some energy which can drain the battery.
In general a storage voltage of 3.4-3.6V per cell should be just fine.
