Any innovative solutions for adding more batteries?

I agree. Everyone thinks Yamaha and Honda are the cats meow but onans are the best (only?) generator that will fit under a van. Why don't Yamaha and Honda get into the rv generator business? Probably because it's difficult to do. I just used my Onan 2800 an hour ago sitting on the beach above Ventura to use the microwave. It was awesome! I will be getting an inverter setup soon but for longer uses the Onan will do fine. Respecting others around us of course.