BE24 Model Battery Equaliser.
This battery equaliser is designed to be used with 12V lead-acid batteries. It is compatible with Gel, Flooded and AGM style lead-acid batteries.
When two or more batteries are connected in series, the battery voltages may become slightly different. This can cause an imbalance when charging and discharging the battery bank, which will shorten battery life. The equaliser will shunt current from the higher voltage battery to the lower voltage battery.