Victron Energy - Battery Balancer - (charge level equalizer)
The Battery Balancer balances the charge status of two 12 V batteries connected in series or of several parallel strings. If necessary, several balancers can be connected in parallel. A 48 V battery bank can be balanced with three battery balancers.
Victron Energy Smart BatteryProtect
The Smart BatteryProtect separates the battery from the less important consumers before it is completely discharged (which would damage it) or before it no longer has enough energy to start the engine.