Electrical connection

Relay or not the RV and truck will be fine if connected while the RV is plugged in.
Worst case the truck battery will stay charged.

'02 F250 is disconnedted from RV by a relay when engine is off.

Thank you for your replies. I was just going to do it the day before I leave.

MFL has it right. You will not be affecting your truck battery at all unless the truck is turned on. There is no 12V power to the RV unless the key is in the run position, 02 Ford F250 have a relay.

It probably won't hurt anything, but I can see no good reason to do it. Why make the electrical system more complicated than necessary?

I was told by a battery wizard, that every battery in a system sinks to the level of the worst battery in the system. My Chevy is hot to the RV when plugged in. I am no battery wizard myself, but the odds of one of my house batteries being below optimum and pulling down my two truck batteries is not a remote possibility. I keep my truck batteries isolated from the 5er when not towing.

I also keep my truck running and hooked up to operate the slide, landing gear if I am not on shore power. Lessons I learned on my old truck, which needed every bit of amp the two batteries could provide to start.

sail2liv wrote:
My connection pins are hot all the time.....so if plugged in will drain truck battery eventually.....if using current over time....2500HD

I think you are right if 2500HD means chevy PU. Ford puts that line through ignition don't think chevy does. If I owned a GM product I would use a relay in that line.

Keeping unit plugged to 110 should keep house battery charged so little to no drain would occur on truck battery....

My connection pins are hot all the time.....so if plugged in will drain truck battery eventually.....if using current over time....2500HD

Unless you have altered the charge line, in the Ford, the battery wire in the connector will be dead, without the key in the on position (engine running).

So yes, in your case, it would not matter.

Jerry