My travel trailer has the battery charger under a cabinet out of the way. It is plugged into a dedicated outlet that is not on the same circuit as any other plugs as it cannot draw power from the rv's built in inverter.....a battery charger trying to charge batteries being powered by an inverter off those same batteries would be really cool but it's just not science that works
So, this outlet only powers the charger when the trailer is plugged into 110v ac power. I bought a really nice generator/inverter that is remote start and even though it has a delay feature on the output they still recommend unplugging all the power drains before start up and shut down. In the trailer the only thing I could not control with a switch was the battery charger. I had to work one armed, laying on my side, with tri focals, in the dark no less, up hill both ways, in the snow but I cut the neutral leg at the back of that outlet and ran some wires over to a cluster of other switches and outlets and cut in a new switch and wired it up so I can cut the power to the charger on start up and shut down of the generator. I had all the parts except for the switch plate cover.
I called a local RV place and asked what they do and they told me the switch was the easiest way and they could do it for $400. Ouch......it cost me less than $5 in parts, some skin off my right arm, and three Motrin...I'm good with that!