Workings of a dual-voltage battery

September 1, 2008 | By Richard Prince


How does a dual-voltage battery work? I have a 1947 Chrysler which is still in the original 6-volt configuration. Will a dualvoltage battery work on the starter motor only? Will it automatically change to 6 volts after cranking or does a relay or switch have to be installed? This would save a lot of time in changing bulbs and all of the other things I would need to do in order to change the car to 12 volts.


A dual-voltage 6-volt/12-volt battery is essentially two 6-volt batteries in one housing. When the two 6-volt batteries are linked in series they comprise a 12volt battery and when they are linked in parallel they function as a 6-volt unit.

You do need a switching device to change the configuration and this most commonly is the ignition switch itself. When the switch is in the “start” position the batteries are in series and the starter motor and ignition system get the full 12 volts and then when the switch is in the “run” position the batteries are parallel and the car’s electrical system runs on 6 volts.