Hey all. I think I have a dead cell in one of my packs. I have a 12s4p 30Q battery. I was having much more noticeable voltage drop when I rode my board last - certain hills that I had been able to get up without any issue were now not possible - the board was slowing down a lot more. I didn’t have time to look at it, so I took the overall voltage down to what I thought was a reasonable storage charge of 4.07. I’ve now had a chance to look at it (disassembled) and all the packs were at 4.07 still. Then I started the board and ran it a bit and tested each pack - the one pack dropped immediately to 3.8. I’ve now removed this pack and want to figure out which cell of the 4 is the problem, but I don’t know how. Can anyone advise please?
Not sure where you read that but thats way too high for storage, I’d say 3.5 per group. Maximum, minimum 3.3
It may take a few cycles for the pack to be back in good shape if in storage long.
If you have 4 cells ready to evaluate and all of them have the same voltage. You can either put a load across each cell to see of any of them sags exceltionally much(I sudgest 1-2C as a start). Or discharge/charge to see if they differ alot in capacity/IR.
Thanks @linsus. I did a capacity test after checking the voltage and the one cell was FAR below the others, so I’m assuming that it’s the problem.
Re the storage amount - thanks for the advice. I can’t think why I thought that was a reasonable amount…
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Sounds like you found the culprit 
good luck!
Im in the process of rebuilding that pack - just need a decent soldering iron! Frustrating when my tools break!