I wanted to be able to attach a box of batteries to the back of my utility closet door, so I made a solution to this non-problem!
The box stores batteries at a 45 degree angle, so it can be used standing or laying down. It has many customization options. Choose what kinds of batteries, how many per row, how many rows, where the mounting brackets are, the padding between cells, etc. Handles AAA, AA, C, D, and 9V using the Customizer. I did NOT include support for flat cell batteries. As you may see I just jammed them in a 9v slot.
If you know a little OpenSCAD, you can easily add your own battery types with some light variable tweaks! Add storage compartments of any size using this method!
Fair warning, this is NOT efficient to print. My demo took 22 hours to print at 0.2 SPEED setting in Prusa slicer (all defaults). I'm sure with some setting fiddling you could knock it down, especially if you switch out a larger nozzle. Be careful lowering the infill too much though, those mounting tabs rely on it too! You don't want to go hang it up and have them go crunch. I used washers to help with that.