Another option might be a DC to DC charger.
I did a write up on my install.
https://www.montanaowners.com/forums...hlight=charger.
We are currently traveling and have completed a 4 day boondocking stay on Ocracoke Island on the OuterBanks NC. The weather was perfect. We actually did not have to use it. Our 400W solar panels and batteries got us through. In fact we ran out of water first. The morning we left the batteries were down to 20%. As we go up the East coast we are anticipating boondocking again in Maine for a week.
For running the air conditioner on a small generator, you may want to look into installing a Soft Start on the AC unit.
https://www.rvtravel.com/rv-electric...-hrdl-testing/