Coast PX1 (light) conversion to 18650?

[MyHeadHz]

I'm judging the plausibility of converting a light to take standard 18650 cells from AAA cells.  It might just be a pipe dream, but I'd like your opinions before I discount it completely.    This is mostly for curiosity and fun, but it could prove useful.

I have a Coast PX1 (a very popular flashlight) that I really like, except for the fact that it doesn't fit 18650 cells.  In some other lights you can just grind away a bit of plastic and you're good to go.  With the PX1, it is aluminum.  Also, a full 10 mm would need to be taken out, and there just isn't a way to do that.  The only solution seems to be creating a tube extension.  I've searched and the only one I've been able to find is this one, with a million different listings.  Unfortunately, the dimensions don't seem to be compatible with mine, though I'm not sure about the measuring standards of such things.  I wonder why there is only one option for one particular light, when there is probably a huge market for such adapters for other popular lights...  ohh, well.

(some measurements at the bottom for reference)

There seems to be quite a bit of room to work with, given the ID (of the metal tube) vs the OD of the 18650 cell.  I don't have a lathe, but I do have a 3d printer.  Think that could work?  I've only ever printed and slightly modified existing 3D designs, but I've never created one from scratch.    The threads would be too fine to print, but I might be able to adjust the diameter to "cut" the threads with the adapter itself on the first installation.  Casting (lost PLA) would likely be too difficult for me with such a small piece.

Another idea would be to cut up part of the tube from old/dead lights and work from there.  I haven't looked at the pros/cons of that yet.

Any thoughts or input?  I plan to decide what the most likely option is to actually work and then go from there.


Fit with an 18650 and the spring compressed.  Not even close :p


An 18650 compared with the standard AAA battery assembly.


What the light looks like stock.

edit: some measurements:

58mm original overall length of battery adapter group
22.5mm diameter (overall diameter of battery adapter)
23mm Inside diameter of metal tube


69.5mm (measured) length of 18650 (with nipple and protection circuit)
18.5mm (measured) battery diameter


118mm original overall length.

129mm approx final length, with an adapter

[MagicSmoker]

This seems like too much trouble for the reward. How about seeing if a smaller standard cell size - like, say, 18500 - will fit without requiring modification.

I'd also check the brightness when supplied by 3.6V because I have several Coast LED flashlights and headlamps that are noticeably dimmer when I use Ni-MH cells (1.2V nominal each, instead of 1.5V).

[mikerj]

Most of these flashlights use the body for the ground return to the cell, so a PLA extension tube would need to incorporate a conductive path.  This would be a nice little job for a small lathe.