You can connect your inverter directly to your house batteries. RV's have two electrical systems, one runs the engine electronics, headlights, etc., and the other runs the electrical devices for living in the RV such as interior lights, water pump, heating fan, etc.. Each system has its own batteries. Many RV's have two or more house batteries. Most are parallel, but some are in series. You will have to note that before connecting anything directly to the battery posts. You might consider putting a fuse inline for your inverter as well. Damaging the house system can be pricey.

There are three or more ways to charge your batteries: (1) run your autmotive engine (2) run your generator (3) plug into a 110 volt AC. Some RV's also have solar panels to keep the batteries charged. This is very handy at a place like Burningman, but requires a little maintenance to dust off the panels each morning.

Do not let your batteries run flat. If you do it just a few times, then you might find that they will not hold a charge anymore. I did this the first time I used a travel trailer with batteries. I destroyed the batteries out of ignorance on the first trip. My neighbor just got an RV and let his batteries completely drain on their first weekend at the beach. He had to replace his batteries with his new rig only two weeks old.