Hearing Aid 312 Battery Case

This slim screw-top case holds up to eight 312 hearing aid batteries. Screwed tight, the case measures about 0.5 inch thick by 1.75 inches in diameter (12.3 x 44.6mm). It's smaller than retail battery packaging (fits easily in jeans small pocket) and offers easy tool-free access to fresh batteries.

You can make two versions: magnets and no magnets. Both use the same lid. (You supply ix 6mmx3mm Neodymium magnets).

The case works fine with or without magnets.

You can print a simple one-color no-magnet version without adjusting the files. Just load the lid and no-magnet base in your slicer, slice and go. But if you have a printer capable of multi-color, separate the lid and base into parts in your slicer and color the lightning bolt and stars. The stars indicate the top of the case, so you don't accidentally open it upside down.

For the magnetic case insert a pause in your slicer, add the magnets at the appropriate time and continue the print. I used heat-shrink tubing to attach a small magnet to one side of a flat-bladed screwdriver as a placement tool. The magnets I used are a tight fit: I had to tap them into place. If your magnets are a bit smaller, add a drop of CA glue to each magnet to hold it in place. If the magnets are too big, adjust the model size.

Once seated, the magnets grip the batteries in the case, even if you flip it upside down. When you insert them, the batteries seem to resist placement even though they are not themselves magnetized. I found that it was easiest to put them in tab-side down after sliding them to the holes.

Printing is straightforward: PLA, PETG, ABS etc. I printed mine in ASA. No supports necessary.

Special thanks to David Copete at DCO, who designed a very smart Rhino-Grasshopper script for making threaded caps. I used this in the course of developing this model. Rhino's Texture editor provided easy-to-use grip surfaces on the lid and base of the case.