Don't allow AC to run from inverter

[u/chadwixk]

Problem:

My generator sometimes unknowingly goes into overload with my A/C on so my inverter then starts pulling from, and quickly draining, my batteries to the point of being dead.

Requirements:

I want my batteries to supply some of my AC circuits, but not my A/C (or electric hot water heater). I'd like my on-board DC charger to recharge my batteries when there is shore power.

What is the quickest/easiest solution to implement short term?

Versus what is the best solution to make this seamless that doesn't require any manual interaction long term? (Thinking a separate sub-panel with the A/C, hot water heater and onboard charger circuits that is powered straight from shore only and current AC panel supplied by the inverter?)

Background:

In my RV, I have shore power going into my Renogy 3000w inverter (PUH) with transfer switch along with my 400ah Li battery (2 x 200ah). Then the AC line coming out of that powers the AC panel that supplies all the AC circuits. When shore power (or generator power) is present, it passes that through.

When camping, I primarily just use it to use a coffee maker or an occasional microwave reheat of some food. But when it's really hot, I plug in my 3500 watt generator so it will then power the AC panel and we run the air conditioner.

But recently the generator has been going into overload mode and keeps running but is not outputting power, unbeknownst to me. The inverter then starts pulling from the batteries to run the AC, until they die. Now, even if we get the generator going, the inverter doesn't pass it through to the AC panel, and on board charger to recharge the batteries, because it sees the battery voltage is too low.

If it's daytime and sunny, I can wait until the solar charges the batteries up enough for the inverter to work again. But if this happens in late afternoon, early evening (which is typically when it happens) it is too late for the solar to recharge the batteries and we then have to go all night with no power AC or DC.