Series LFP and low temp shutoff

[JAS]

Hey all,

I already have a Rebel 300AH 12V battery. I'd like to add another in series to create a 24v system. Wondering, However... What happens in cold temperatures during charging if one battery's BMS initiates a low temp shutoff before the other?

Thanks,

Jeff

 

[BentleyJ]

A series circuit only has 1 current path that flows through all the components in the system. If one BMS trips then the circuit is open and current stops.

 

[JAS]

In the case of the Rebel BMS, it will shut down charging below freezing, but will still allow discharge. Wouldn't this mean that the circuit is still closed?

 

[BentleyJ]

In the case of the Rebel BMS, it will shut down charging below freezing, but will still allow discharge. Wouldn't this mean that the circuit is still closed?

The type of BMS you are describing uses 2 sets of UniDirectional power FET's. So Charging can be disabled while discharging can still occur because current can flow in the opposite direction through the other set of FET's that are still closed.

 

[JAS]

So... In summary... Are you saying it is safe for the batteries if that happens?

 

[BentleyJ]

That's what the BMS is for to protect the battery from permanent damage so yes its safe for the battery.
Is it good for the charger to suddenly get disconnected while under load? Probably not but batteries are expensive so better to stress the charger and save the battery.