On my 2007 232 EXP, I fabricated a tray to hold 2 batteries. It took the place of the single battery tray.
Another option is to carry a second battery in the truck, fully charged, and use jumper cables to tie it into the first battery for extended times. They both will charge with the generator as well.
2017 28BHBE Kitchen skylight, remote control and Aluminum wheels hitched by ProPride 3P
2012 Jayco Jay Flight 26BH traded in
2013 Toyota Tundra DC 4x4, 5.7, 6 speed 4.30 gears