3D Printed Battery Adapters

These adapters are 3D printed in PETG or Nylon filament (not the more common PLA which is not as resistant to heat and solvents) with solid brass and stainless hardware where needed.

Adapters with * have built in mechanical reverse polarity protection and require a button top or a raised positive contact. Protected cells are recommended.


Most of the adapters have been sold elsewhere, I still have a few if you are interested please PM me for prices and details.*



14500 to 18650 adapter.


18650 to 3C (red) and 3D to 3C (blue) adapters.


2C to 2D adapter.

Hey, these look nice! I don’t need one myself, but it looks like good work to me.

If you want your pictures to show up in-line, you will need to add a “!” to both sides of the link.

I like to also define a relative width (typically use 40) so it doesn’t display an image larger than the screen (really annoying on mobile). Anything up to 100 should be fine.

To get them to display, either use the “insert image” button or type the code into the editor (click the “quote” button on my post to see how I did this). Then your images will display on the forum like so:

Thanks Much F0xx! I appreciate your help and kind words.

This one is the CR123A/16340 to 18650 adapter.

This is the 18650 to 2C adapter:



Those are pretty cool.

THAT is a very cool idea.

Thanks everyone!

I like C and D cell lights but I don’t like using alkalines and I like to have lights that can run on different “fuels”. The 3D printed adapters came out pretty nice, which is why I an offering them here.

Since Mag-Lite uses very chunky springs for the tail, I’d prefer the 18650 be in the middle of the adapter in this case, if possible. Could you make one that way? [Note: I’m not ready to buy right now, so don’t do it just for me.]

That’s kinda what I did for the D cell lights by using two adapters, one to change D cell to C cell and the other a C cell to 18650. There is a washer on the base of the D cell to C cell adapters that mates with unmodified Mag D cell springs so that there is no need for a spring mod.

I find that the smaller springs on C cell Mags work fine with 18650’s and even smaller cells.

I am working on a 21700 to 2C adapter. 21700’s maybe the ultimate “fuel” for a 2C light in terms of run time - I don’t know of anything with more Watt hours that will fit in a unmodified 2C tube.

Have you tried printing a 3C to 2x 18650 adapter for Defiant 3C light? The two 18650 cells would be connected in parallel to extend run-time. My Defiant 3C eats through a single NCR18650B cell very quickly.

I haven’t done a 2 18650 cell adapter as of yet, with 2 protected cells there is only about 10 mm left to work with to fit everything in.

PM sent…

2 D cell to 26650 adapter that I have been working on:

I have sold most of these elsewhere and only have a few adapters left. Due to lack of access to a 3D printer during virus shut down, I will not be printing more for a while.

One of the last ones I completed is a 26650 to 3D cell adapter:

6D to 2x18650 adaptor?
Just kidding :slight_smile:

If I ever get a 6D ML300, I might come up with something to run a couple 26650 specifically for a 6D but 2 of the 3D to 26650 adapters would work just as well.

I am starting to print some of these again on a limited basis.

OOoooh - Aaaah ! Yeah !

I was wondering what to do with my 3D Printer .
One of these days I will have to print a flashlight .