If the only 12 volt
system you will most likely be using is the lights why not just take a 120 volt light with you and unplug the converter to be safe.
If not you will have to cover the end of the positive cables to be sure they don't short to ground while plugged in.
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles