Electrical connection

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.