How to Add a Battery to an Enclosed 6x12 Cargo Trailer for Powering Interior Lights.

Updated 09/27/2019 | Published 09/26/2019

Products Featured in This Question

Trailer Wiring Junction Box

(821)

$31.83

10 Gauge Wire - Blue Primary - Per Foot

(104)

$1.84

NOCO Genius Smart Battery Charger - AC to DC - 6V/12V - 5 Amp

(156)

$69.95

Buyers Products Trailer Tongue Toolbox - Black - 18 x 19 x 36

(79)

$181.53

Adapter 4-Pole to 7-Pole and 4-Pole

(659)

$61.55

40 Amp In-Line Circuit Breaker - Perpendicular Mount Bracket

(97)

$9.84

Opti-Brite 12V LED RV Dome Light - Single - 11" Long x 4" Wide - White Housing

(650)

$45.86

Question:

I currently have a 6 x 12 trailer that has a 4 way flat wiring harness. when plugged into my truck and the lights are on and I can switch on my interior cargo lights. How do I add a battery that can run these lights when I am not hooked up to my truck and can this battery be wired so it charges by my truck when it is running? Also is there a good small cargo box that would mount in front of the trailer before the Manual Crank Tongue Thank you

asked by: Tadd T

Expert Reply:

So the right way for you to do this will depend on how often you're going to use the lights and how many of them there are. If a trailer isn't equipped with a battery, the interior lighting is frequently tied into the running lamp circuit. Turn on the vehicle's running lights and boom, on come the lights. This is the simple way to go. You'd obviously need the truck there and plugged in to make that happen. You'd also want to run the truck from time to time so the alternator keeps the vehicle battery charged. LED Lamps like # ILL06COB would be ideal, if you don't already have the lamps.

For an independent set up, you'd need to install a 7-way trailer connector on the vehicle, and make sure that the pin in the 1:00 position is ran to the battery terminal. Probably the easiest way to do this would be with an adapter like # 37185. Mount the 7-way connector to the vehicle, and plug the existing 4-pin harness into the 7-way. Ground the white wire to the vehicle, and extend the black wire with a length of # 10-1-1 to the positive battery terminal, routing it through a 40 amp circuit breaker like # 9510. On the trailer side, you'll also need a 7-way. I'd recommend using a trailer side 7-way/Junction box like part # e99011. This will allow you to neatly and easily tie in the 7-way to the existing trailer wiring. All the connections will be easily accessible, yet protected from the elements. You'll want to tie the interior lamps into the black wire from the trailer connector, and also to the positive terminal on the trailer mounted battery. Keep in mind, the connection of the battery to the 7-way trailer connector will keep a maintenance charge on the battery, but will NOT recharge it when it's discharged. For that, you'll need shore power and a battery charger like # 329-GENIUS5.

As far as a cargo box goes, that's going to depend on what kind of space you have on between the front of the trailer and the jack. If you have 19 inches of space available, the # 3371701680 would be a good choice. The cargo box would be a great place to mount the battery so it's out of the way.

I've linked you to the trailer tongue toolboxes we carry, and also to an install video for the wiring kit and a product description video for the toolbox I mentioned.