# Rechargeable Unprotected 18650 Li-ion Battery in Surfire G2



## nightstalker101 (Dec 3, 2006)

Hey, I am new to this site, and thought I'd try it out. Well I was wondering if anyone had ever tried to put a 18650, li-ion battery in a Surefire G2. I have had my G2 for about a year and would like to upgrade to rechargeables. I am looking at either a 17670 or a 18650 rechargeable battery. I have noticed that a primary CR123a there is room around the battery (using surefire brand batteries), this made me wonder if the 18mm 18650 battery could fit. If any knows the exact internal diameter of a G2 body or has tried putting the 18650 battery in a G2, please let me know.

Also, any idea on wether or not I sould use protected or unprotected? Lighthound recomends unprotected for incandesants because they will shut off when the batteries get too low (without over-discharge). Also unprotected batteries are half the price. Thanks for your time.

nightstalker101


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## dizzy (Dec 3, 2006)

First off, welcome to the CPF. There is a wealth of information to be had here, but not that much by me.

All I can tell you is that an LG-18650 will not fit in the G2, and if it did, you would need to put in a 3.7volt lamp assembly from another manufacturer because the original lamp is designed for 6volts.

I'll let others answer about the protected/unprotected part. I use an unprotected 18650 in my U2 because it will stop working before you over discharge the cell and it works great with the light.

I'm sure someone with alot more knowledge can help you out more.


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## leukos (Dec 4, 2006)

Here you go, mate: http://candlepowerforums.com/vb/showthread.php?t=127715


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## Owen (Dec 4, 2006)

nightstalker101 said:


> Lighthound recomends unprotected for incandesants because they will shut off when the batteries get too low (without over-discharge).


Protected cells will cut off, not unprotected(that's part of what "protected" means).
18650 won't fit in a G2, and you won't be able to bore it out. Have to use the 17670.
The LA AW is selling looks like a G&P, and should work fine in the G2. The Wolf-Eyes LAs will also work, but you'll need to turn the optional "Surefire spring" around so the smaller end(which normally fits tightly on the backside of the LA) can hit the end of the sleeve that the G2 uses for ground contact.
Another option is 2 R123s with a 9v lamp. Shorter runtime, but more output. 
I'd recommend you put a UCL in your G2, either way, but particularly if you go for the hotter 9v. That's "ultra clear lens" from flashlightlens.com. I think lighthound.com also carries them. 
I use a G2 with 2xR123 and a 9v LA as one of my work lights, but am planning to try out the 3.7v one that leukos linked to.


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## nightstalker101 (Dec 4, 2006)

Thanks for the help!, also, I have herd of people running their 6V P60 lamps on 3.7V rechargables, first of all, dose this work. Second will it damage the bulb. I guess I was mislead by Lighthound about the unprotected batteries. (Lighthounds site says "_Over-discharge is rarely a problem with these batteries, as incandescent flashlights will shut off and stop drawing current, and most LED flashlights will begin blinking rapidly."_)


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## Brighteyez (Dec 4, 2006)

A 4.8V bulb is going to be kind of dim if it's running on 3.7V, but it will probably light up. 

A colleague did pick up an Ultralast RCR123 3.0V kit a while back and has been using it with his G2. Apparently it works well and hasn't blown the lamp assembly. I didn't have anything at work to measure the output voltage, but if he hasn't blown the bulb after a couple of month's usage, it is probably okay. I did try the batteries out in my TL-2 and they seemed to be about the same brightness level as the primary batteries.

The kit with a charger and 2 RCR123 batteries goes for about $25 in Fry's stores (and for the web shoppers, thanks I know I can find them for $15+change, but it still comes out to about $25 after you factor in the $9.99 shipping/"handling" charge. Unlike the Tenergy RCR123s that cut off right at the 1.3A point that prevents their use with incandescent lights, the cutoff point for the Ultralast seems to be set higher. 



nightstalker101 said:


> Thanks for the help!, also, I have herd of people running their 6V P60 lamps on 3.7V rechargables, first of all, dose this work. Second will it damage the bulb. I guess I was mislead by Lighthound about the unprotected batteries. (Lighthounds site says "_Over-discharge is rarely a problem with these batteries, as incandescent flashlights will shut off and stop drawing current, and most LED flashlights will begin blinking rapidly."_)


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