Originally Posted by scrubjaysnest
This is a hard question to answer since it varies from model to model and within a model line.
The computer(s) that Ford install for the engine are powered all the time for sure. on our Axis the camera splitter is powered all the time.
There is also line from the parking break and something that looks at if the coach is in park that feeds the camera system to turn on the radio.
Batteries also self discharge about 1 to 3 percent a month.
I have a Mercedes Chassis Thor 2018 that had the chassis battery dying, even after replacement by Mercedes. What I found was, one of the overhead buttons by the lights was depressed (on). I turned that off and no further problem. The button was depressed but no light was on.