I only have 2, 12 volt batteries, ( GP 31, 105 AH type ), and have dry camped overnight many times.
We use lights, inverter powered Sat. TV, and run a coffee maker in the morning. On more then one occasion, we have also run the furnace on the cooler nights.
The bateries are still strong enough to start the generator.
We do have 400 watts of solar but that doesn't do anything overnight.
If you can't get one night on your batteries, you don't need more batteries, something else is wrong.