18650 Adapter

[jebatty]

I hope this is not a repeat and is useful.

1) An emergency backup for a 18650 is easily made from a cr123 (3v) non-rechargeable battery + a spacer made from 1/2" copper pipe with end caps to make a battery the same length as a 18650. Wrap the copper with electrical tape for insulation.

2) A 18650 + the same spacer in 1) will also replace 2 - C cells, and these can be placed inside a plastic water pipe cut slightly shorter in length than the 18650 + spacer. I used the black plastic water pipe that is commonly used underground for well piping. This replacement battery fits very well in a 2 - C cell flashlight, and provides slightly higher voltage and a brighter light. I use it for my MagLite, in which I also have replaced the incandescent bulb with an LED bulb.

 

[fivemega]

Each rechargeable 18650 has about 3.7 volts under load and up to 3400mAh capacity.

Each primary CR123 has about 2.6 volts under load and up to 1500mAh capacity.

So your lamp/module may perform poorly and run very shorter.

For same reason many people use 18mm bodies instead of standard 16mm bodies.

I would personaly get some extra good quality protected 18650 cells if extended run is required or simply get the host for this purpose.

For 2C size M*g host, you can use deep tail cap and use 2x18650 or even 4 CR123

PVC tubes are also available to use for this purpose.

 

[jebatty]

All valid points. My focii were 1) "emergency replacement" of a single 18650; 2) replacing 2-C cells with an 18650 in any flashlight which uses 2-Cells end to end; and 3) one spacer serving two uses. My total cost of implementing these ideas was $0 because I had everything on hand, for others the cost wold be nominal, and everything is standard stock and readily available.