I am going camping tonight with my boyfriend and we plan to sleep in our cars, if I were to leave the hatch open (it is an suv) and turn off the lights and sensors for when the lights open when the doors are, will my battery die?
I drive a 2009 Hyundai Santa Fe and the hatch wouldn't be open all night, just for about 5-6 hours while we watch and cuddle by the fire.
Depending on the age of the battery and condition of the alternator, it may nor may not. Too many variables to know for sure. The best thing to do it you are going to leave a door/hatch open is to find which fuses control the light and sensors then pull them temporarily while you have it open all night. I say that because you can never really be certain with today's cars that you've truly killed everything.
You should be fine simply turning the lights off, or pulling the fuses if he knows what he's doing. Never simply disconnect the battery on a modern car though, you can sometimes end up 'bricking' them.