@RR_NDB
32 V was designed due BDM (diode module)
32.2V is end of charge voltage (4.025 x 8).
29.7V is rated voltage.
I'd go for 25V being available when battery low and at a high current load.
I estimate that BDM drops less than 1V (0.8V typ) at 150A if based on Schottky diodes and less than 0.5V (0.3V typ) if based on MOSFets.
NiCad rated bus voltage is about 24V and end of charge 29V for 20 cells. End of charge less 27-28V at elevated temperature.
What really happened?
Just random? Coincidence?
My best bet, as outlined in earlier posts, Primary failure (short) due to gradual cell deterioration after one or more (in no particular order of preference) of :
- Mismanagement by BMS.
- Mishandling (assembly, rework, repair, maintenance, storage)
- Mishandling deep discharge and reset BMU lockout
- Mishandling external over voltage, such as bus over voltage, also during maintenance or storage (recharging - dunno they do that).
- Tested to overstress - Boeing says they test a lot and hard (unlikely IMHO)
- Bad cells (unlikely IMHO)
Edit: Apparently, current battery tests do not detect cell deterioration. I do not claim that tests possibly could detect it.