3D Printing a battery box holder for a mason jar style firefly light

We put together some firefly light jars for some accent lighting.  The light is an LED string dropped into a jar powered by an AA battery pack.  We originally just dropped the whole package into the mason jar. Using them without a cover was kind of cumbersome because you had to reach your hand into the jar every time you wanted to turn them off.  

I found a plan on Thingverse and adapted it to better fit our needs and battery pack.  The design attached the jar like any of the two-part lids.  We just drop the lid part and retain the threaded attachments.

The Plans - The Video and All That

In Use - On the Jar

Drop the string of lights into the jar.  Slide the battery pack into the slot at the top. Push the wire into the slot on the side of the lid.  Insert the mount with the batter pack into the jar. Screw it down with a canning lid

It might look a little better printed with a clear filament inside the jar.  The black works fine though.

Prototyping different sizes

The battery packs slide into the top in the same way on all three versions. 

The original design is the one on the right in all three pictures.  I had problems with it because of the wide tolerances for the opening on the ball jars.  It wouldn't insert all the way in most of my jars.

The second design is on the left.  It is the same height as the original but the wide section extends as far down as the end of the mouth. This seemed to avoid the tight-neck bottle problems.  

After creating the second design I realized that my battery pack slid too far down into the unit essentially blocking the switch in the off position on the lip.

The third design is in the middle. It is 20mm (or is it 30mm) shorter than the other two.  This lets the switch still be accessible while the battery pack sits on the bottom of the plug.

These pictures show the sizing problem with the IKEA battery pack being too short for the original design.

Revision History

Created 2023 03


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