How To Wire A Battery Charger From A Motorhome To A Towed Vehicle

Question:

I have a motorhome with a 7 pin electrical connection that I use when towing my Jeep Wrangler which has a 4 pin connector. I use a coiled 7 pin to 4 pin coiled connection. I am adding a device on my Jeep that will keep the Jeep battery charged while being towed. I know that there is a generic + terminal on the 7 pin connector as well as a ground, but I’m trying to figure out how to get to that connector with the power and ground wires from the charging device. I suppose I could wire into the running lamps pin on the 4 pin connector but I’d rather not. What’s the best way to wire this up? Im attaching pictures of the connectors I currently have. Thanks!

asked by: Dave D

Expert Reply:

It sounds like you are trying to keep your Jeep Wrangler's battery charged while being towed by your motorhome. The most common way to do this is by using Roadmaster Battery Charge Line Kit for Towed Vehicles # RM-156-25 which connects to the 12V hot pin on your RV's 7 way connector. If your 7 way does not have a 12V pin then you will also need to use Roadmaster Battery Charge Line Kit for Motorhomes # RM-156-75 which connects to the RV's battery then connects to the 7 way to provide 12V. If you are using a different charging method/device then you can disregard the charge method mentioned above.

Now, in order to run the 4 light wires along with the added power and ground wires that you are using with your charging device, I recommend installing Hopkins Endurance 6-Way Trailer Connector # HM48440. This will attach to the front of your Jeep (tow vehicle) and allow you to plug in a 6 way cord, then the output end allows you to run 6 wires which will be enough for your application. Then you will need to add Hopkins Endurance Flex-Coil Trailer Connector Adapter w/ Nite-Glow - 7-Way to 6-Pole - 8' Long # HM47053 to connect your RV's 7 way connector to the newly installed 6 way connector at the front of your Jeep.

You will want to grab some 10 gauge wire such as 10 Gauge Primary Wire # 10-1-1 (sold per foot) to run from the power and ground pin on the 6 way connector to your Jeep's battery. This will be everything you need to neatly and safely add charge lines to your towed vehicle. I attached demonstration videos along with a wiring pinout for the 7 way to 6 way flex-coil.