Call the mfg, they'll tell you how it should work.
Different manufacturers (and sometimes differences even within the model lines) use different approaches.
Some deploy for the chassis battery:
- a trickle charger, like a
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This converts 120vac to 12vdc
- an amp-l-start
AMP-L-START Starting Battery Charger/Maintainer - Overview Page
This diverts some power from the house batteries (which are charged by your converter), and charges the chassis batteries.
- turn on the charge solenoid or BIRD, which periodically connects the two battery banks together.
- some coaches don't have anything
Your mfg can tell you how your coach was built.