Wiring to Charge Trailer Battery from Tow Vehicle

Question:

I have a enclosed cargo trailer with a seven way connector. I removed the small 12V battery for the breakaway braking and added a full size automotive type 12V battery in its place. I did so in order to have lighting inside the trailer and to power the electric tongue jack I installed. The way I have it done, I can have lights and power to the jack whether or not connected to the tow vehicle. I have everything working properly but the trailer manufacturer did not provide wiring so that the battery recharges from the tow vehicle when connected. When I took delivery, the dealer made a special point to tell me that I would have to keep the breakaway battery charged because it would not charge from the tow vehicle. I currently have a solar cell mounted atop the battery box and connected to the battery but, of course, there is no voltage regulation. How can I change the wiring to allow recharge off the tow vehicle and do away with the solar cell?

asked by: Ken

Expert Reply:

The 12V battery on your trailer can be charged from your tow vehicle by simply running 10 gauge wire # 10-1-1 from the 12 volt circuit on the vehicle side connector to the positive post of your trailer battery. This will provide a maintenance charge when connected to the trailer, however it will not provide enough output to charge a depleted battery.

If you need to charge up a dead battery, you will need to use a charger like the CTEK Universal Battery Charger # CTEK56353 when 120V AC power is available. I have attached a short video demonstration on this product that you can also check out.

expert reply by: Chris R