2 XPG-2 w/ CR123 internal batteries w/ usb
I have been intrigued w/ a light w/ internal batteries.Matt's version w/ usb charging really got me thinking. What do you think of a scar style sled light using rechargeable CR123s instead of 18650s. I believe you can get sanyo CR123s w/ 1400mAH rating. Driving the two xpg-2 leds at 1000mA should give 600+ out the front lumens w/ ~ 1.4 hr. runtime, if my calculations are correct. It should be a "relatively" standard build using 1" aluminum tubing from the hardware store, maybe adding some cpu heatsinks on the exterior for heat dissipation. I like the form factor of a 2" x 2.5" light. Could be even smaller if an exterior switch was used.
Even more lumens w/ an XML but so many people are talking how great the throw is on the XPG-2.
Are my calculations/assumptions even close to being correct? start shooting holes in it guys
sorry about the hole, but...
CR123a is a primary (non-rechargeable) battery.
RCR123a would be the rechargeable version. The 3.6v nominal voltage models (A.K.A 17340) are 750mAh at best. The 3.0v LiFePO4 versions are less than 500mAh.
Good concept .should be a practical light.
Using a battery from full to empty will yield half as many charge cycles till failure as using a battery from full to half charged.
A little bigger on battery or lower on drive current would be better.
Also that size has a low energy density compared to good 18650 size.
You should look at cheap nano lithium polymer ala hobbyking.com. Square batteries for a square design should let you pack in more.
interesting idea, although those batteries would have to be wired in parallel if you wanted to use a USB charger (and li-ion/po too). I think you can get the brightness and run time you want with a single XP-G2/XM-L and a 18650, especially if you stump for a 3100 or 3400mAh battery, plus the housing needed for all that will easily keep it cool - I think mine has something like 20sq.in. of surface area for a ~6W light.
It wouldn't look as cool as your idea, but it would be easier to make
Thanks for the info Ryan, now it makes more sense why they aren't used as often. At about half the mAh this light may not meet my requirements for commuting or two of them for the trails.