Can the Trailer Breakaway Battery be Used to Power a 12 Volt Interior Light

Updated 01/03/2012 | Published 01/02/2012

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10 Gauge Wire - Blue Primary - Per Foot

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Question:

can the breakaway battery be wired to the trailer wiring of an enclosed trailer so it would power a 12volt interior light when the trailer isnt connected to a tow vehicle so it has no power source for the light

asked by: Roger O

Expert Reply:

You will want to use a standard 12 volt deep cycle trailer battery to operate the interior light. You will NOT want to use a trailer breakaway battery. The breakaway battery is not designed to power other trailer accessories or lighting, it is just designed to operate the breakaway system. The DOT regulations state that a trailer breakaway system needs a dedicated battery.

To keep the trailer battery charged you will need to run a 10 gauge power wire like the, part # 10-1-1, from the 12 volt power pin (# 4 terminal at 11:00 position) on your trailers 7-way connector, to the positive terminal on the trailer battery. Now when the trailer is connected and you are towing, the tow vehicle will provide a maintenance charge to the trailer battery. It will not charge the battery from a discharged state.

You will want to test the # 4 terminal at the 1:00 position on your tow vehicles 7-way connector for power with a circuit tester like part # PTW2993. This is the terminal that will supply the 12-volt power to your trailers 7-way connector. If it does not show power, you may need to insert a fuse and/or check that the wire is connected to a power source by tracing the wire back.

I am sending a link to a FAQ page on trailer wiring diagrams, which will show the 7-Way connectors and which pins are for what functions.

expert reply by: Jeff D