Abstract: A battery isolator for selectively connecting a pair of batteries to each other to allow both batteries to be charged by a charger connected to one of the batteries while allowing the batteries to be separately discharged. The batteries are selectively connected to each other through an electronic switch. The system includes an analog-to-digital converter for measuring the voltage of the batteries, and a microprocessor for opening and closing the switch as a function of predetermined relationships between the measured voltages of the batteries.