I have a small (but awesome) system with Victron BVM 712, Solar Charger, Battle Born batteries in my camper. When I have the tow Jeep connected, I can see on the 712 a discharge of 5 amps or so. When I disconnect the discharge goes back to under 1amp. It is negative number, I'm sure it is a discharge.
I know about the battery separators, etc. and could technically use one. But I don't need to separate charging onto two batteries. I wondered if there is something to just block the flow into the Jeep. A big diode? :-)
Jeep Grand Cherokee 2018 Limited with idle shutoff and a lithium battery.