BatteryProtect disconnects the battery from insignificant loads before it is completely discharged (which can damage the battery) or before there is enough power left to start the engine.

BatteryProtect is a one-way device. It can only operate with current in one direction, ie either current to the load or current from the charger, but not both at the same time. In addition, current can only flow from the battery terminal to the load terminal. When used with a load, the battery connects to the Battery terminal, but when used with a charger, the charger connects to the battery terminal.