Abstract: A control circuit for connection between a battery charger and a battery being charged, which includes a control switch in series between the charger and battery for disconnecting the battery under a variety of conditions including improper connection, loss of battery charger power, improper connection, and shorting of terminals. A switch connected in the series between a battery charger is closed in response to a low voltage condition in a battery and is open in response to a fully charged condition of the battery. An over-current circuit opens the switch and disconnects the battery charger from the battery when excessive currents are detected in the control system. An under voltage circuit also keeps the switch open when low voltages are detected prior to connection to a battery thus protecting the circuit from short circuits and similar mishaps in the connection of the charger and battery.