I have a Ford E-450 Goshen with a handicap lift. I'm trying to confirm it does in fact have battery isolation from the main battery. I wonder the current rating, too. The battery isolator I bought says 700 amps. It's pretty chunky.
I did buy two different devices to help with converting it to a motor home, a battery isolator and a 110 vac automatic switch.
It seems likely there already is an isolator, which would be wonderful if true.
The other quest is to add a much larger battery compartment. I've seen doors for compartments but wish there were water tight boxes, too. The current aux battery is much smaller than I expected.
Ironic I have a box and pan brake and likely could build one if I had time to. I weld but somehow don't have sheet metal welding skills; if it's much thinner than 1/8" I usually don't weld it, I just create lots of holes. Even worse, I have oxy-acetylene and a wire welder. My biggest inhibitor is not having a foot shear. Some day ... some day.
The Goshen is a practice run for my Freightliner bus conversion, coming later. I'm trying out both shuttle and bus conversions eventually. Both have handicap lifts, BTW. The Freightliner is good in the underneath compartment area, it has several.