BMS Shutoff?

[John.DS99]

Do BMS systems all work the same or could it be unclear when they are doing their job of protecting the battery?

I ask because I keep hearing about restarting the BMS after an overcurrent or improper battery voltage. Attach a battery charger to get it running again etc.

I have overused a battery on the bench a few times where I check the battery and it might read 3V. If I leave it alone, it recharges the next day when the sun comes up. I'm not using a charger so no restart is required. I don't understand this, did the BMS do that or not? How would you know?

 

[Ampster]

Do BMS systems all work the same

My guess is they are different. Mine is a Orion BMSJr which traces it heritage to EV conversions and uses a contactor and that means it could be configured for charging even though discharging might be disabled.

 

[mikefitz]

I have overused a battery on the bench a few times where I check the battery and it might read 3V. If I leave it alone, it recharges the next day when the sun comes up.

Once low voltage protection had activated, say at 10.5 volts for a 12v system, the load is removed and the cell volts will increase slightly, perhaps reaching recovery volts set at say 11.5 volts. It depends on the levels set in the BMS. Note, once in protection the voltage at the terminals is not the 'true' voltage of the series cells, due to the fets being in the off state.
Of course if you have a solar controller that doesn't need to 'see' battery voltage to start charging, ( all Victron and some Renogy solar controllers, perhaps others), it will charge the battery. Note for a fet based BMS, a low voltage disconnect only disables the discharge path, the charge path still functions.