Do a energy audit or otherwise determine if one battery is adequate for boon docking or even 2 batteries along with gen run time. If they are the same connect them in parallel and see what happens. But carry jumper cables and perhaps a battery pack.
There are options for larger batteries including deep cycle batteries. Everything can tie together including your charger and it's capabilities in terms of charge time/gen run time.
2009 Holiday Rambler 42' Scepter with ISL 400 Cummins
750 Watts Solar Morningstar MPPT 60 Controller
2014 Grand Cherokee Overland
Bob