Hearing Aid Battery Holder - Keychain

Update 5/28/19: As requested by calania 1mm diameter was added to the bottom part of the design to prevent common breakage at the thread location. This also required an extra 1mm be removed from the Top threading to allow for the larger bottom diameter. The latest files for print are the HearingAidBatteryHolderTop/Bottom - 1mm Diameter Added.stl. These files were test printed at .1 resolution w/support everywhere and printed out perfectly.

I am always looking for inspiration for my projects and this one was provided by my dad. He recently got diagnosed with tinnitus and got prescribed a set of hearing aids. He has been much happier and is able to hear things he thought he never would again.

However he expressed how often he was replacing the batteries and how they always seemed to go out at the worst times. A month ago he had asked me to make him something he could use to keep spare batteries on him when he is out and about. I had him provide me a few of the size 312 Zinc-air batteries in order to get the correct dimensions.

I spent a few nights planning out a design in my head that would be safe, compact, and easy to access. Came up with this last night and sketched it out in Fusion 360. I was really impressed to see my first prototype print fit together perfectly. Only had to make a few cosmetic adjustments to get this design just the way I wanted it.

I decided to align the torus shaped keyring cut out with the position of the battery tray and added a raised arrow to to make sure it was easy to identify the top of the tray so the batteries would not accidentally spill out while opening. I also used supports between the tray dividers which make them print straighter and adds a little extra material to keep the batteries tight but still easy to pull out.

Thought this was a really cool design and very impressed with the results. Hope you guys enjoy.