Ultrafire C2 and 2X 3.7v AW 123A's?

First, Thanks to everyone who has done great reviews on the ultrafire c2 cree light. Most questions have been regarding the use of the big 18.... single battery. I was more interested in using 2 AW 3.7v 123A rechargables for a flatter 100% regulated output. I imagine it would run for 70+or- minutes like my Huntlight.

When I looked on Ultrafire's site, it says the light is fine with 6 volts, but somewhere here at cpf, I read it could handle up to 9.

Any input would be greatly appreciated, and again, thanks for the great reviews and photos.

I don't notice much of a drop in output after running my light for ~2 hours on an 18650, and there is hardly a difference in brightness between 1x18650 and 2xRCR123, so you might as well just go for the larger battery. When I get my lux meter next week I'll post some lux vs. time plots for different battery setups.

BTW, dealextreme.com lists the light running from 3.6v to 9v. Testing current with my multimeter indicates that it has at least a buck circuit, as current draw was lower on the 2xRCR123 setup.

Thanks for your info and help! I was just looking at the curves from threads here and flashlight reviews for the Huntlight and Lumapower M1 and they seemed to drop below 80% after an hour. I look forward to your results.

ok Ive been running 2 (3.6v) batteries in my c2 and there's a pretty big difference in output but am I going to burn something out? The only dealer that says its ok for 9v is dx. But hes pretty good about these things. does anyone know for sure?

ok Ive been running 2 (3.6v) batteries in my c2 and there's a pretty big difference in output but am I going to burn something out? The only dealer that says its ok for 9v is dx. But hes pretty good about these things. does anyone know for sure?

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So far the only thing I've been running in mine for any extended period has been 2X 3.6V CR123. Power draw is a constant 4.5 watts from the tailcap depending on the voltage of the batteries -- about .56A on freshly charged CR123s (8V), and I tested .75A on primary CR123s (6V). Both cells draw the same power, and deliver (from what I can tell based on ceiling bounce) the same light. That tells me the voltage is not a problem at all. Keep in mind that the driver is probably around 75% efficient, so that's well within safe limits for the LED. Based on current draw, and nominal capacity on those cells, around an hour runtime seems reasonable. However, current draw on one cell (18650) isn't as much, .54A, or about 2W so the output is dimmer, but shuold last a lot longer. Since the light is primarly a "throw" light though, I think higher output/shorter runtime is probably a good tradeoff, as I find I don't use throw lights for extended periods as much as "flood" lights.

I did a few rough calculations by measuring current draw and battery voltage and found that with 2xRCR123s my C2 draws about 4.8 watts of power, and with an 18650 it draws about 3.6 watts of power. Last time I looked I must have used some discharged RCRs as it is noticeably brighter using them instead of the 18650.

and with an 18650 it draws about 3.6 watts of power.

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You were seeing 1A of current from the 18650? I'm only seeing about .5A out of mine. Sure you didn't multiply by 7.2 by mistake (voltage assuming 2 cells)?

I am seeing about 850mA draw from a freshly charged 18650 that read 4.22v when not under load, so approximately 3.58 watts. I'd say its safe to assume the LED is getting about 2.5 watts on an 18650 after compensating for driver losses and voltage sag.