I have a block diagram of this rig's electrical system, so that's where I'll start tracing. I think what I'll do right away is remove the house battery and bring it home, where I have a charger and can see what the battery's condition is and bring it up to full charge.
Getting it checked under loan at AutoZone or some such is a good idea, and easy to do here.
My plans has been to take the rig for a drive every week or so during the "season "for a number reasons, one of which is battery health.
Storing it where there's AC just isn't in the cards right now.