I'm very new to this forum and have recently purchased a 2012 - F250 to tow my 5th wheel RV. Can anybody tell me if while towing my RV, does the 7 way electrical plug that the 5th wheel is plugged into charge the battery in the RV? In my F 150 I had to install a relay and fuse but none was provided when I bought the 250.

 

Most if not all do charge. It is not fast, I amped mine out and it was 10 amps peak.

 

The trailer has to be wired to work that way. Older campers, the aux charge was just for the breakaway battery.

 

Also the truck has to be FUSED and RELAYED for power to get to the back of the truck

 

My 2012 F250 Lariat came wired that way, didn't have to do anything. I did notice it only has power when the truck is running.

 

that is just battery isolation. If you leave two batteries in parallel for long periods of time one will almost certainly drain the other due to minor differences in voltage and internal resistance.

 

Should be a fuse and relay in the fuse panel to make it charge while traveling. Usually a 30amp fuse

 

In the power distribution box under the hood, Fuse #90 (25 amp) and Relay #102 both have to be present for Trailer Tow Battery Charge to be fully functional.

 

Correct ^^^