Power to the hatch door

I'm in the middle of replacing my audio unit. First thing - disconnected negative terminal. Couple of hours later, when the work is finished, reconnected the terminal. Noticed that back door doesn't have power - hatch open button and the small button which locks the car doesn't work. The power is there - ACC mode fine, new audio unit works fine.

Noticed the kind of switch which is mounted on top of the 12V battery - what is responsible for?

 

Turns out is was a 12V battery sensor (that switch). I've pressed open button on the remote twice and it enabled the rear door's open button. Problem solved.