Hi Steve,
You did not mention what you own, brand, model, model year, etc. That might help.
Here are a few things that come to-mind, especially with an older motor home.
Open all your outdoor compartments. Maybe the lights were left on in one or more of them. If you have florescent lighting, one of your lights might be on, the bulbs just didn't light up. A florescent light fixture might also be faulty.
The one inverter still connected, don't just turn it off, as an experiment, disconnect it and see if that makes the difference.
Most RV roof antennas are equipped with a 12v signal booster of some kind that stays on all the time unless you intentionally turn it off. Locate it, turn it off by pressing the tiny button, and see if your drain is gone. It might use a lot of electricity or it could be faulty. Look for something like this near the TV. My signal booster runs hot. I turn it on only when watching antenna TV.
Install a cheap 12v volt meter, somewhere in the house in a place you can see. If you have a 12v outlet, plug one into there. I got fancy and installed one that also displays the time and temperature, in the kitchen hood/vent. Ebay sells both types very cheap. It helps me to always know the battery voltage, when they are draining, how fast they are draining, also when and how much they are charging.
