Only a few days away from finishing testing, cleaning the last of the cells. All up I count about 1100 @1500+ most are around 2300-2700. Have only had to redo the shrink wrap on about 200
I'll be taking the best 960 which will hopefully have a lower cut off somewhere around 2000mah. This will be separated into 8 packs by grouping cells in 100/50mah increments and filling each pack with the same number of each capacity. When each group is not divisible by 8, the remainder will be something something something averaged and spread even across the packs. Hopefully that gets each within an acceptable margin.
Why 8 packs for 24v? It's going to be in a van , something of course will go wrong when away for a lovely weekend or in the middle of nowhere, so I'll be building 7S120P + a spare 120P that will stay fully charged, but disconnected from the main pack unless needed (I'll have a separate charger maintaining it at top voltage ~4.05v). I plan to use a decent BMS, so hopefully swapping in a pack with a slightly different voltage in will balance out without catastrophic failure. By having it at the top voltage, the BMS will start discharging it to match the other cells rather than dragging all the others down to meet it. If I go with Batrium, I'll add a few more long mons on the spare pack to help with swift correction. Once an offending pack is fixed, it will go back in, so the average health of cells should stay roughly even across the packs. The only other option I came up with was 7S60Px2, but this had it's own challenges and honestly wouldn't fit the space quite as well.
Next steps:
-Run an IR tester (from Aliexpress) across all of them. Discard any over 150.
-Test voltage drop on the newer half (first half already done)
-Solder/tin the newer half that pass
-Separate into 8 equal packs (7S +1 hotswap)
Waiting on:
-6AWG busbar copper wire
Future John's problems:
-Turn metal storage box into fancy battery storage whiz bang power wall container
-Spend stupid amount of money on BMS (Probably Batrium)
Thoughts? Suggestions? Eeeek?
J