Using an Auxiliary Vehicle Battery to Run 12 Volt Power on a Trailer  

Question:

Expert Reply:

The issue is that if you have batteries mounted under the hood of the truck and you are trying to use the electrical system of the batteries to charge a trailer battery you will not be able to achieve sufficient current to charge up the battery, only maintain the charge that is already in it. Using the 12 volt power circuit on a 12 way will accomplish this task.

You would route a wire from the 12 volt pin from the back of the trailer side connector to the positive terminal of the battery on the trailer and ground the negative terminal to a clean metal surface on the trailer frame.

Another way to do this would be to use a battery isolator, # DW08771, if the truck had 2 batteries and you were using the auxiliary battery on the truck to run power on the trailer rather than trying to charge a battery mounted on a trailer.

This would keep the auxiliary battery from using power from the main truck battery when the truck is not running. First you mount the isolator. You run a heavy gauge wire from the positive terminal of the main battery to the isolator. You then connect a wire from the isolator to a 12 volt ignition source. This source will allow the power to flow from the main battery to the auxiliary battery as long as the truck is on.

Then you run a wire from the other side of the isolator to the auxiliary battery. Anything that runs off the auxiliary battery would also be connected to the positive terminal on the aux battery. The closer the two batteries are to each other and the shorter the wires are between them, the better the charge will be to the aux battery when the truck is running.

expert reply by: Michael H

0