HELLO! New to forums and new (to me) camper (1995)

Do you have any way to measure your current amp draw? With the fridge on electric, the water heater trying to heat up and other misc stuff going on, you might be exceeding what's available via your household outlet.

Converters can "chatter" if they don't like the power they're getting. And, yes, that could harm your new batteries.

A "kill-a-watt" electricity monitor would be a good thing to have in your tool kit.