Conveniently charge multiple batteries from a single charging source, without requiring any system modifications. Simply connect to the primary battery, auxiliary battery and ground for installation. The battery separator waits until the battery connected to the charging source reaches approx 13.2 volts, before paralleling it and charging the auxiliary battery. The battery separator also assists in engine starts. When the starter is active, the primary battery voltage is compared to the auxiliary, and if it is lower, they are paralleled together, so the auxiliary can assist in vehicle starting.