18650 cell adapter tube

I looked around for available cheap tubing to adapt diameter of 18650 to battery chamber of some flashlights designed for round 3AAA holder, but are long enough for the 18650.

Ordinary 3/4" PVC water pipe OD was good but the walls are a bit to thick, ID too small. I found a piece of thinner-walled tubing with same OD, and it works great.This came from a solar driveway marker support which was no longer being used. The first piece I cut was a bit too short which allowed it to move back and forth inside, probably harmless but annoying.

OD = 22.2mm
ID = 18.5mm

I found some lights were better cutting tubing slightly longer than the cell, about 70mm overall in one case.


Dave

I found the adapter tubes on Ebay awhile back for cheap.

I imagine one can get just about anything online, shipped to you (from China?) but this is DIY with material people may already have around, perhaps sitting idle, therefore costing nothing more than the time to cut it.

My tubing looks like PVC which unfortunately is not easily recyclable around here, and much of it ends up going out in garbage (though a last resort for me). This is good, albeit small, reuse.

Dollar stores might be a source of tubing from broom/mop handles etc. although some are thin metal. I'll check this out.

Tube can be cut with hacksaw but small pipe-cutter makes nice smooth cut.


Dave

I bought a plastic dustpan with 2-foot tubular plastic handle for $1.25 at Dollar Tree. Outside is ribbed and slightly smaller than the previous tubing (which was nearly perfect fit), might benefit from a wrap of tape. Inside diameter was snug so getting cell in and out was a bit of a chore. Anyway, it would provide about 8 sleeves; dustpan still usable with shorter or no handle. Dave

You can wrap electrical tape around the middle of the 18650 if you don't have a tube to get the right fit – the problem is that cheap 3 AAA lights usually depend on the high internal resistance of the three alkaline or zinc-carbon AAA cells to limit current. Li-ions cells will overdrive the LEDs considerably and together with the typical lack of heat sinking will cause the LED's to over heat and slowly dim/burn out.

xxo said:

You can wrap electrical tape around the middle of the 18650 if you don't have a tube to get the right fit – the problem is that cheap 3 AAA lights usually depend on the high internal resistance of the three alkaline or zinc-carbon AAA cells to limit current. Li-ions cells will overdrive the LEDs considerably and together with the typical lack of heat sinking will cause the LED's to over heat and slowly dim/burn out.

Click to expand...

I had an 8 LED 3AAA light that I put nimh in and burned out the LEDs. I replaced them with warmer colored ones and installed a resistor in the tailcap to limit the current and it worked perfectly increasing runtime about 2 times over cheap alkaleaks.

Certainly one can wrap cells with all sorts of material such as thin cardboard, or half a roll of electrical tape, but a simple tube which can be instantly transferred to another cell or light and may cost next to nothing seems the way to go.

As for AAA flashlights burning out prematurely with Li-ion/NiMH cells, that would make a good topic for a different thread. All I'll say for now is that any light which relies on battery impedance to such a degree sounds like a poor design.


Dave

Before I got into 3D printing, I used to make simple spacer tubes out of news paper – all you have to do is cut some news paper to a little less than the length of the cell, loosely wrap it so the cell will slide in and out and keep wrapping until you get the right diameter (might require some trial and error) and secure the roll with some Scotch tape. Costs nothing and actually works fairly well and with a little patience you can get a perfect fit.

After burning out several cheap 3AAA lights with Eneloops, I would be real cautious when converting to Li-ion. A 3AA light needs to be regulated and have a good heat sink to run NiMH or Li-ions.