It’s me, Alex, reporting back.
I went and tested 6 of the 10 packs of my 10S4P battery and got the following results (the official capacity of each pack is 8800 mAh):
(By "Cell 1" I meant "Pack 1", etc)
That surprised me, because I was pretty sure that packs 1, 3, 4 and 5 where the most likely to be damaged (on account of their usually being more discharged than the rest). It turns out that they’re mostly OK, except 5 which is clearly not.
After this testing, with some packs completely depleted and others close to full capacity, I hooked the battery to the 42V charger to see how the BMS (which may or may not be working correctly) would handle the balancing. I unplugged the charger every 15 minutes and measured each pack.
This is what I got:
The results left me puzzled, really.
At some point (around 60 minutes into the process I think), the red light in the charger turned green, which I took to mean that the process was done and the charger had stopped supplying current to the battery. This is clearly not the case; I think the green light comes on when some of the packs are fully charged, but the charger still feeds the battery so that the BMS can continue with the balancing.
Then I left the battery alone for 3 days and measured the voltages to see if any of the voltages had dropped significantly : only #1 had (3,26V to 3,18V).
Then I hooked up the charger, but the green light came on immediately and no charging seems to have taken place after that (even though the voltages are all over the place and the total voltage is barely 36,94V!).
Can we conclude anything about the BMS from this little experiment?