Hedges
I See Electromagnetic Fields!
- Joined
- Mar 28, 2020
- Messages
- 20,680
4) Voltage gets to 3.65V and BMS disconnects the battery. PVs suddenly get in open circuit mode, and the voltage spikes to max PV voltage (i.e. 200V).
5) The BMS gets toasted right after point 4. The sudden voltage spike was over the FETs max voltage capabilities.
Won't be instantaneous so long as there is a capacitor involved, e.g. on SCC output. Inverter would have even more, but no guarantee it is connected.
10A into 1000 uF would be 10,000V/second or 100 microseconds per volt.
I wouldn't count on an interpreted language, but compiled dedicated code could be fast enough. I prefer analog hardware.
A transistor circuit could be fast enough, so long as drive of FET gate is strong. Relay or breaker would be questionable. In 1 millisecond voltage would have risen 10V, and we may have 20V headroom in BMS FETs.
I think tripping a breaker works if done before BMS disconnects (or for my AGM).
Where a BMS could trip, either turn off a series MOSFET to open circuit, or turn on a crowbar MOSFET to close.
One issue with the crowbar is that assuming failed SCC, it is sinking current through SCC and from battery. That besides capacitors of the SCC.