How to Connect Spare Battery to Trailer 7-Way  

Question:

Expert Reply:

To connect an auxiliary battery, I recommend using 10 gauge wire, like # 10-2-1 (per foot) to connect the 12V power wire on your trailer side 7-way connector to a junction box like # 38656. From there, you can run more of the same wire from the positive side of the battery to the same post where you previously connected the 12V wire on the junction box. To connect to the posts, you can use 3/16 inch ring terminals # 44-5310A.

If you don't already have a junction box, the 7-Way Molded Trailer Plug with Junction Box # HS381-9000 offers a simple solution. It comes pre-wired for you. So, all you have to do is connect the positive battery terminal to the 12V post with the black wire on the junction box and the negative battery terminal to the ground post with the white wire on the junction box with the same wiring and ring terminals mentioned earlier.

Connecting the battery in line with your trailer wiring will allow your vehicle battery to send a maintenance charge to your trailer battery when connected and also allow you to power interior lights or other accessories through your auxiliary trailer battery, when your camper is disconnected from the tow vehicle.

expert reply by: Carla M

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