Abstract: A control circuit including a relay switch having a fixed terminal adapted to be coupled to a terminal of the battery or the charging source, a normally-closed contact terminal adapted to be coupled to a terminal of the other of one of the battery and the charging source, a normally-open contact terminal, and a relay coil. The control circuit further includes a comparator circuit for coupling to terminals of the battery to sense the voltage of the battery, and coupled to the relay coil to energize the relay coil causing a connection between the fixed terminal and the normally-open terminal of the relay switch when the voltage of the battery exceeds a first voltage threshold and to de-energize the relay coil causing a connection between the fixed terminal and the normally-closed contact terminal of the relay switch when the charging voltage of the battery falls below a second voltage threshold.