@RR_NDB
CVR/FDR are recorders for investigative purpose.
QAR records more in detail, with maintenance in mind.
Subsystems do their own recording. Frequently, investigations looked for example at FADEC NVM.
So far, there is no hint on availability of any per cell recordings. Sensibly, the BMS would record (amongst others) things like
- Event time stamp
- Cell #
- Cell voltage
- Cell short/over voltage/under-voltage
- Charger on/off
- Failure notification
- Breaker tripped / disconnected
- Battery temperature/fire
At BOS smoke/fire was observed, but no hint on any prior battery related alert.
IMHO, NTSB based their BOS related analysis, as of 6 Feb brief, on FDR (32V, no overcharge), and on physical evidence / examination after disassembling battery and cells.
We know that 32V during a cell short will result in destruction of remaining cells. To figure it out, the following info is needed.
- Battery temperature history
- Per cell voltage history
- Per cell voltages prior to Primary failure
- BMS response to Primary failure
- Battery voltage after Primary failure - Has it reduced or remained at 32V
- Precise failure sequence