You might get a more-focused audience in the Sprinter and B-van forum IMO:
. . . plus there are a variety of battery use threads there already.
I have added the headline above, and the bold comment below, in hopes that the replies here will be on-topic for your specific unit. Recent motorhome threads have wandered off-topic fairly dramatically IMO.
Welcome to the forum, Josie, and good luck!
Attention future posters -- this thread is about an Airstream Interstate motorhome.