This is for use with Xenon and LED flashlights/weapon lights.
As I understand it, I can replace two CR123A batteries with a single (rechargeable) 18650 battery.
I’ve gleaned from numerous 'net threads that I want to ONLY use ‘protected’ 18650s, with UltraFire and Tenergy brands being recommended most often, but there seems to be no clear preference when it comes to chargers.
What do you folks use?
Thanks,
mbogo
Batteries here: http://www.lighthound.com/AW-18650-Protected-2600-mAh-Rechargeable-Lithium-Battery_p_3125.html
Chargers at the bottom of the same page.
You definitely want AW’s cells as they are some of the best produced.
However, you need to make sure your light can handle the higher voltage of the 18650.
Thank you. The WF-139 charger was one mentioned frequently. I had not heard of the AW batteries.
mbogo
Hello,
Ultrafire and sundry brands use Chinese-made cells. These cells are a hit and miss when it comes to capacity and amount of usable cycles before they give in. Worst case scenario the cells are plain defective and cause a fire in the light or worse, when charging and unattended.
Lithium cobalt batteries (if you see any 18650 with a stated capacity above 2000mAh it’s a LiCo) are inherently unstable and can cause fires if mistreated (or plain badly made…). I would not skimp on these, for the sake of your pants, what happens to be housed inside the pants, the house, and family in the house the batteries are being charged in…
You have to remember these are loose cells that are usually put in laptop packs by OEMs. When you have off-brand Chinese manufacturers taking the same cells and a cheap protection circuit, then marketing them for hobbyists, you some times get bad results.
There are really only two 18650 brands I would trust - Redilast and AW. AW may say ‘made in China’ on them, but the cells are Panasonic. Highest quality cells on the market. AW’s protection circuits are also good and reliable. Redilast uses the same Panasonic cells, and also Samsung cells. Panasonic, Samsung, Sanyo, LG make good cells. If there’s no spec sheet or info on what cells are being used… Well, I wouldn’t buy it, would you? 
On another note, if you have a caliper, go ahead and measure your CR123 batteries’ dimensions. They’re slimmer than 18 millimeters, aren’t they? 18650s are 18mms wide, 65mms long and cylindrical, hence the name. Most CR123 lights will need to have their inner diameter bored out to fit 18650s.
The only drop-in replacements for CR123s unless your light has been made to take the wider 18650 are RCR123s and 17670s. RCR123s look like rechargeable CR123s and 17670s look like two of them glued together. Not that they are, just talking form factor here.
Another thing you need to keep in mind is that two CR123s will deliver 6V to the emitter (bulb or diode/driver circuit), whereas a single rechargeable lithium battery will deliver 4.2V at most and 3.7V under load and then decline steadily. If you want to use a single li-ion rechargeable, make sure your light will actually run on that voltage. If you want to use two in series, make sure 8.4V won’t fry it.
Unfortunately replacing CR123s with rechargeables in lights not made for them (like, well, all Surefires) can some times be a headache. Some Surefires accept them from the get-go, others are fiddly, others have caveats and asterisks attached to such use. And, of course, it’s not covered under warranty.
As for, uh, the charger (that’s what the thread was about, wasn’t it? sorry :() - I use the Pila IBC. That’s all I can talk for, but others speak positively for the WF-139s. Oveready sells them, pretty good endorsement in my book. Oveready doesn’t bother stocking stuff that’s not up to par.
I have a couple WF_139’s that work fine and seem to terminate charge fine and don’t charge above 4.2v. (Where other chargers have problems and can cause kabooms.)
However, I couldn’t resist buying a couple Pila chargers as well to have even more peace of mind when charging. I got them here and they ship quick and are very responsive.
http://illuminationgear.com/14343.html
AW batteries are the only way to go as far as the best chance at safety.
Dennis.
Thank you, all. you’ve given me some good information to ruminate over.
mbogo
Another vote for AW protected 18650s and a Pila IBC charger.
Although seriously, I’d stay with primaries for a weapon light unless its just for recreational use.
I second the vote for the Pila charger. I have one and it is good equipment.