Dala, re-using both the cells and the BMS! Cool.
With the BMS under close observation now, I am wondering if you have gained any insights into how it is deciding which cells to bleed energy from? I have read so many conflicting ideas out there.
Things I think are true: When the BMS is getting 12 volt power, it can (and very likely will) be actively bleeding energy off for a subset of cells, through the tiny resistors assigned to each cell pair. No 12 volt, the BMS is powered down--does nothing. When the car is off--no 12 volt to BMS.
Things that might be true: The BMS can remember what cells it wants to bleed off for some period of time.
Things I am very curious about: How does the BMS select which cells to bleed off? Does is take a snapshot of all cell values at some level of battery SOC and go from there? How is it measuring the resistance of the cells? Voltage drop under load, or perhaps under charge, at some (or many) amps?
If you have any insights, I would very much like to hear them.