Using a Switch and Trailer Mounted Battery to Power Interior Trailer Lights  

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What I recommend is to wire up the lights via a switch installed inside the trailer and connected to the battery. You can mount the battery where needed but 10-gauge wire will be too large for lights. A lot depends on the lights and how much power they draw but 16-gauge wire such as # 16-1-1, sold by the foot, would likely be all you need.

For a switch you could use something like # PK34513. It is a basic on/off toggle switch rated for 10 amps. Another option is # PK33300 rated for 20 amps when used with a 12-volt system. On either, on wire or terminal is the input from the battery and the other is the output to the lights.

To provide a maintenance charge to the trailer battery it will need to be connected to the 12-volt circuit on the trailer connector. This circuit usually does not have power with the truck turned off on factory towing packages. But to be sure you can test the vehicle side connector with the truck off using a circuit tester such as # PTW2993.

If it does have power with the truck off then that is when you would need to install an isolation solenoid, # PK5231201, on the 12 volt circuit, truck side, to prevent the interior trailer lights from draining the trucks battery when the trailer is connected and the truck off.

The battery would not be able to get overcharged because the tow package wiring is too small and the alternator not strong enough to push back the amperage needed to charge up a battery. But it will maintain the charge level the battery has and not let it discharge any more. If you need wiring tools and accessories I also recommend wiring kit # HM51020.

To protect the battery inside the trailer I recommend using a battery box such as # DW03188 or a similar product for the size battery you use. I have linked a video showing our installer mounting a battery box inside of a trailer.

expert reply by: Michael H

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