Li-Ion 18650 Battery Protector ...and more

thingiverse

I want to give credit to enif for solving the dreaded contact solution for battery boxes, and his post on wrapping wire around is a great solution. I was trying to optimize a battery holder for hobbies, but my early versions were all too tight. I decided to make use of my printer's inability to fill 1mm walls, which makes for a perfect spring at both ends of this Li-Ion cell protector. This device has good range for battery sizes, although it is targeted for protected cells which are typically 2+mm longer. The design distance between contacts is 68mm. Another notable aspect of this design is that as you expand the ends, the sides pull in, sort of like a finger puzzle. Although the overall structure is pliable, a battery will have a hard time being knocked out of the frame. The idea here is to make your protected 18650 Li-Ion cells safer to carry by letting you dump your spare cells in your backpack with little worry of shorts. This little frame acts as a backup protection to the cells' internal protection. Some of you may see the use in making this a battery holder with leads, and I find wrapping the wire tedious (22awg solid) so I got out some copper foil. As you can see in the images, this is a very easy implementation. Copper, brass, and stainless steel foils are available at your local hobby shop. And of course, this is only the main structure - I'd love to see some remixes where multiple boxes are ganged together and a base is added. For now, I'll leave this for you good people to play with, and I will get on with the project these are intended for. Tech details: The active spring region is 1mm thick; prefer no fill. The typical wall is 1.8mm to ensure 2-trace wall thickness (2 in + 2 out=4 total). The upper and lower cell-retaining ridges are different so there is a top and bottom, normally it won't matter but as you fix this to other things, it may. I recommend you print this with a minimum of 4 walls. As to material, anything should work - I recently began printing with PETG, which works well for this. But please don't use any of the exotic conductive materials; they will drain your batteries before you ever get to use them. Edit: 12/6/18 - I've added the 2x 18650 cell protector, and this one too converts easily into a battery holder.