How to Install a 12v Wire on a Horse Trailer to Charge a Trailer Battery

Updated 03/17/2010 | Published 03/16/2010

Question:

The truck is a standard factory 7-way and the trailer was a 6-way, so I used a adapter. I recently changed the plug on the trailer to a 7-way and it worked great. The trailer wires go to a junction box on the trailer and all connections are made there. The 12v hot wire working but not hooked up to anything, so that is why I was wondering if I could go straight to the on-board (trailer) battery to maintain the charge while driving. Thanks

asked by: Charlie

Expert Reply:

Why type of plug does your 2006 Ford F-350 currently have? Is it a 6-way, or a 7-way plug? Does your horse trailer have the same style plug, or do you use an adapter? Please let me know and I would be glad to offer a solution for you.

expert reply by: Sarah L

Charlie

3/16/2010

Sarah L.

3/17/2010

If the center prong on your 7-way plug is wired for reverse lights and you don't need it for your particular trailer or if it is not connected at all, you could wire the 12v auxiliary wire from your vehicle 7-way to a 12v auxiliary post near your battery or fuse block under the hood. This way, you could connect the auxiliary wire on the trailer, which is usually purple or yellow orange, to a post in the junction box, and wire your battery to the same post. You can also just install the 12v power lead wire from your trailer connector to a post in the junction box and hook your battery wire up to the same post, if the auxiliary wire is already in use and you need it for a reverse function. If you do this, the battery charge would be maintained as long as the trailer is plugged into the vehicle. However, you would have to make sure that you unplug the trailer when you park so that the vehicle battery is not drained.