AC240/RV Setup

I recently purchased a Bluetti AC240 and am looking for guidance on the best way to integrate it with my small travel trailer.

I have a 2019 nuCamp T@G with a 12V marine lead-acid battery and the factory small solar panels mounted on the trailer.

I understand that I can simply plug the trailer’s 30-amp shore power cord into the AC240, but I also realize that this is not very efficient since it converts DC → AC → DC just to run my 12V loads (lights, TV, fan, etc.).

What I’d like to do instead is properly use the AC240’s 12V / 30A DC output to power the camper’s DC system directly.

My goals are:

  • To power the trailer’s 12V DC system directly from the AC240
  • To disconnect the trailer’s 12V battery while using the AC240
  • To be able to switch back to the trailer battery when the AC240 is not in use
  • To avoid backfeeding or damaging either system

What is the correct and safe way to wire this?
Do I need a DC-DC charger, selector switch, or other components to do this properly?

Thanks in advance for any advice or diagrams — I want to make sure I do this the right way.