As with so many things, "It depends"!
It depends on how the coach is wired. It depends on what modifications a previous owner may have made.
I have heard that SOME brands of coaches are wired so the converter charges the chassis ("engine starting") battery. I have owned a Pace Arrow, a Tioga, a Southwind, all by Fleetwood, ranging in year from 1977 to 2002.
I also owned a 1988 Suncrest (an "orphan" brand).
NONE of them were wired so the chassis battery charged from the converter.
None were wired so the chassis battery powered the house electrical system.
I have rarely had a problem with the chassis battery being discharged from sitting for up to 13 weeks. Several months, yes, the parasitic loads are enough to drain the battery.
