Plugged in or not?

If we are overnighting and not unhooking the 5er, cord stays connected to the truck and is also connected to shore power (2012 F350 and previous 2007 F350).

Doesn't your truck have a relay between the battery and trailer connection? My old Ford has one so no problem leaving the trailer plugged in as long as the ignition switch is off. Easy to check to see if your truck has it.

Sounds like you have a back feed into TV.
I would check to see if your TV has an isolation relay to prevent running down TV battery.
Fords have a relay, some Dodges have relays, GMs do not and should have one installed. Something like this style and installation
Battery switch

What you can safely do depends on your truck.

My '06 Ford has an isolation relay, and if the truck is not running, the RV battery is isolated from the truck. The RV cannot run down the truck battery. But if I start the truck, there is a connection between RV battery, truck battery, alternator, and if I was plugged into short power, the linkage would include the RV converter. I consider that risky, so I would do not do that.

I was with a friend when his RV depleted his truck battery overnight. It was a popup with a 3-way fridge, and it ran on 12VDC all night. It was a Chevy from about the 2000 model year, and that model did not isolate.

So you have to know how your truck works, but the safest practice is to not connect to shore power and truck power at the same time. The computers and electronics in new trucks is just too complex and expensive to take unnecessary risk.

My previous Ford with a factory hitch & wiring didn't like staying connected to the TT on shore power. It's headlights would come on and the clearance lights on the TT would come on. The lights would go out if I started it. My current Chevy with same TT doesn't seem to have a problem staying connected.

"best practice" would be to unplug when not moving; rational being to prevent a draw from the trailer side from killing your truck battery or an over voltage scenario on the rv side from back feeding the truck and causing damage.

shore power is providing a charge voltage to the rv batteries which doesn't harm your truck; now if that were to fail and you were to get say 110volt to the rv battery I don't think that would necessarily get back to the pickup but I wouldn't want to try it



personally; my concern is around drawing voltage from the truck to the rv and being unable to start the truck; that is the scenario I'd worry about

If we stop and don't plug into shore power we always unplug from the truck since the draw from the trailer could run down the truck batteries.

If we plug into shore power for just an overnight and we don't unhook from the trailer then we don't unplug from the truck.

We installed a switch on the battery to completely shut off power to the trailer. We have a "Battery Cut-Off Switch" inside the toyhauler but it doesn't shut off all power so we put an actual cut-off switch on the battery itself.

I usually stay plugged into the truck when on shorepower if we are not unhitching for any reason. Never caused a problem.