My old Suburban has two batteries, even though it is a gas job. When I used it as a TV, i would isolate the second battery when I parked, and didn't have to worry if I ran the two TT batteries and the primary TV battery down. Our new Ford F150 has only one battery, but doesn't supply juice to the trailer when the key is off, so I guess it is "isolated" when boondocking as well.
2012 Jay Feather 197 w/pull-out
1997 GMC Sub 1500 4x4;
or 2015 Ford F150 4x4 SuperCrew EB