Batteries produce the voltage they are designed for, so a 12-volt battery always produces 12 volts. If you’ve got an electrical device that operates on 6 volts, connecting it to a 12-volt battery will break it. However, by inserting another 6-volt device, such as a 6-volt light bulb, in series with your other 6-volt device, you can easily switch your 12-volt battery to 6 volts. Wiring two 6-volt devices in series reduces the voltage from the battery by half so each device gets 6 volts.
Cut one strip of AWG 18 gauge wire using a knife. It only needs to be about 12 inches long. You use this wire to connect between the 12-volt battery and the 6-volt light bulb to switch the power to 6 volts.
Remove ½ inch of plastic off both ends of the wire strip with wire strippers. This reveals the copper metal that connects to the 12-volt battery and the 6-volt light bulb.
Attach one end of the wire strip to one of the terminals on the 6-volt light bulb. Hold the wire in place using a strip of insulating tape. Attach the opposite end of the wire strip onto the positive terminal of the 12-volt battery with the tape. The positive terminal is labeled "+."
Attach the end of one of the wires from the 6-volt device you want to power using your 12-volt battery to the other terminal on the 6-volt light bulb using tape.
Attach the remaining wire from the 6-volt device you want to power using your 12-volt battery to the negative battery terminal using tape. The negative terminal is labeled "-." Your 6-volt device and your 6-volt light bulb operate using your 12-volt battery.