How to Connect Wiring to Marine Battery for Interior Lights of Enclosed Trailer to Work

Updated 02/19/2018 | Published 02/18/2018

Question:

Hi, I have an enclosed trailer with electric brakes. I want to install a marine battery inside the trailer in lieu of small breakaway battery. My truck and the trailer have a seven wire set up. I also installed interior lighting and reverse lights on trailer. I want to charge battery when truck is hooked up. I also want to be able to have reverse lights work when backing up. I want to have lights powered by marine battery when truck is not hooked up. I also want interior lights to work even if marine battery is not hooked up but trailer is plug into truck. I do have a terminal block inside trailer to connect trailer plug and lights for brakeslighrs turn signals and running lights. Thanks

asked by: Kenneth S

Expert Reply:

To charge the marine battery in your trailer you need to run some wiring from the pin in the 11 o'clock position on your trailer 7-Way to your marine battery (see attached photo). This should be the same wire that your breakaway kit is connected to.

If you have a junction box like part # PK52248 inside your trailer then you will just need to connect your battery to that 12V power wire. This will charge your battery whenever your trailer 7-Way is connected to your truck.

For your reverse lights to work you need to run wiring from your reverse lights to the center pin on your trailer 7-Way. As long as your tow vehicle is sending power to that circuit when in reverse it will allow your lights to work.

The easiest way for your interior lights to run if your trailer is connected to your truck or not would be to run them directly to your battery. If you wanted to bypass your marine battery whenever your trailer was coupled then that would mean you have to change the circuit that your interior lights are on whenever your trailer is not coupled and you want to use the lights. I recommend just running your inside lights off of your battery since it will be charging anyways.

Let me know if you need any equipment to complete this installation and I can help you out. If your junction box uses terminal then you would obviously need ring terminals in addition to any wiring, switches, or butt connectors.

expert reply by: Jon G