Voltage is defined as a measurement of force to move electrons from a power source to the device it operates. Voltage from a power source generally has to be the same as or similar to the device it operates: If too many volts are applied, the device can be damaged. If you have to start a car that operates at six volts with a 12-volt battery, you will have to reduce the output by wiring another six-volt device in series; this increases resistance and halves the voltage supplied to each device.
Wear protective rubber gloves before using a 12-volt battery to start a six-volt vehicle to protect you from electric shock.
Disconnect the negative battery cable from the car’s 12-volt battery terminal.
Attach a new battery cable to the negative terminal of the battery.
Attach the clamp on the opposite end of the new battery cable to a device that uses six volts. You can use a small motor or a light fixture. Attach the clamp to either of the two terminals on your chosen device.
Attach the clamp on the end of a second new battery cable to the other terminal on the device. Attach the clamp on the opposite end of the cable onto the end of the battery cable clamp you disconnected from the negative terminal of the battery.
Make sure that clamps are not near the positive battery terminal and that the device you’ve wired in series is secure. Turn on your ignition and start your car. The voltage from the 12-volt battery to start your car is now six volts because you have wired a second six-volt device in series.
