Some cells will come back to life, I get around 30-40% usable cells from my old packs.
it only takes one cell of the group of four to develop an internal short and the whole set is unservicable.
I use an imax b6 charger to balance charge the pack without segways intervention,...then do a capacity test on each bank of four....if there is a big difference say 2-300 mA then i scrap the pack and harvest the good cells..I arrange them by individual cell capacity, after a few batteries i have a spare cells that are close enough to match existing cells
Only change just the bad ones if you're on a really tight budget, don't be cheap...buy new, my last lot were $1.50 each!
from my experience the bms does not care who made the cells as long as they are well balanced from a capacity point of view..that's the important bit.
Even new cells can have capacity differences...I match my cells as far as possible,...I capacity test each cell (ebay from china, not accurate I only care about numbers not actual capcity), wite the value on each cell, then charge them (miboxer c8..brilliant bit of gear) arrange them so that the total capacity of each group of four is as close as possible..then assemble.
phwew my fingers hurt now!...
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