This is a compact design for 3 AAA Batteries. I use it for the replacement batteries of my headlamp. Just throw it in your backpack and forget about it until you need it.
The design is greatly inspired by this great battery case from walter: https://www.thingiverse.com/thing:57281
Update 16.08.2018: Okay, that escalated quickly. In order to solve the question if the batteries are full or not I added the symbols on bottom and top. If the batteries are full simply turn the positive pole facing towards the power symbol. If they are empty simply put them the other way round. So if you have a Memory like me can't remember if they are full or not, the package can store the information for you. If you want it super fancy use color change after the first layer. G-Code for Prusa Mk3 i3 is included. Added a slot for easier opening of the case as well.