On our 2015 Greyhawk 29mv, installed two Interstate 6v. batteries with Easy Fill hose setup, in storage bay next to the original 12v. slide compartment, had the battery floor reinforced for the extra weight, works great with way more juice for dry camping.
Use a stove top coffee pot, replaced all the non LED bulbs in the bedroom, microwave, kitchen counter lights, shower etc, just ceiling lights come with LED's btw., to save more juice.
We carry a quiet Honda 2000 generator and plug directly into that after a few days, run it for 6hrs. or so, each day thereafter, to maintain the batteries, will not power the AirrConditioner, but Onan will run that if necessary, but noise from Onan is more than the 2000 generator, so camping courtesy negates using onboard generator too much, never at night in camprounds.
We can boondock up to a week this way, as long as I can get fresh water to refill our tank.