Trailer Battery Charge Recommendation for Battery on Trailer that Has 4-Way

Question:

I have a 2016 Tundra with both a 7 way AND a 4 way wiring harness at the back. I am towing a small popup with a battery in it that I would like to charge from the truck while towing. The trailer only uses the 4 way harness for lights. Is there a plug for the 7 way that can attach to the trailer battery to charge it while towing? Both are keyed, and I am assuming both are also hot when keyed on. If not, is there an easy way to set this up?

asked by: John

Expert Reply:

What you will need to do is remove the 4-way of your trailer and replace it with a 7-way like the # H20042 so that you can then run the black wire of the 7-way to the positive post of the battery so that it charges.

expert reply by: Jameson C