I've dry camped, or boondocked, almost everywhere I've been. I have a standard deep cycle battery, haven't ever run out of power but I only use the outdoor light, overhead light for story time, the water pump, and maybe charge my cell phone. Longest stay was at the beach for 4 days.
There's a switch that disables the lights if the lid is fully closed, on mine it's on the back left corner. If the switch is stuck / not connected, no interior lights for you.
1995 Toyota 4Runner SR5 4WD 5 spd
2002 Eagle Summit 12