How to Wire a 12-Volt Marine Battery Switch

If you own a boat, chances are you have two batteries on-board: a starting battery to fire up your engine, and a deep cycle battery to run other equipment without depleting the starting battery. If so, you need a switch to choose which battery will be used. A battery switch acts as a bus bar so that you have both batteries going to a common circuit. It gives you the ability to change where the circuit goes.

Things You'll Need

• Pliers-type wire crimper
• Screwdriver
• Ring terminals
• Cable

Instructions

1. Crimp a ring terminal onto the starting battery's red positive cable, using a pliers-type wire crimper. Unscrew the "A" terminal on the battery selector switch. Slide the screw through the positive battery cable and thread the screw back into the battery selector switch. Tighten with a screwdriver.

2. Crimp a ring terminal onto the deep cycle battery's red positive cable, using a pliers-type wire crimper. Unscrew the "B" terminal on the battery selector switch. Slide the screw through the positive battery cable and thread the screw back into the battery selector switch. Tighten with a screwdriver.

3. Unscrew the "Common" terminal. Crimp a ring connector on each end of a length of battery cable equal in size to the cable from the starting battery. Slide the "Common" screw through one of the ring connectors, then thread the screw back into the battery selector switch at the "Common" position.

4. Unscrew the "B" terminal on the ignition switch. Slide the screw through the remaining terminal on the wire from the "Common" position of the battery selector switch. Thread the screw back into the ignition switch.

References

• Boatfix: Battery Selector Switch and Master Disconnect--Two Batteries