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KevinL said:
Yeah, Nick has it figured out. The unprotected R123 will do it, but you're slapping the cells with extremely high discharge rates, above 3C. I'm not sure how long the cells will last, some say this shortens their life. If I had to do it again, I'd do it with different cells.
In fact,
I did.... /ubbthreads/images/graemlins/grin.gif though in a MUCH bigger package.
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270Win, KevinL, & others; it is somewhat inaccurate to talk in general terms about battery/bulb combinations. If you take Li-Ion 18650 (like the older ones KevinL likes to take chances with); older, lower capacity versions are lousy under 2C or greater loads, lose up to 50% capacity under such loads, suffer significant voltage sag. It also depends on the
manufacturer (most of the Li-Ion being made in China now so there is a wide range of quality/capabilities; we all ready know that there is a great deal of difference in labeled capacity, capacity under load, voltage sage under load, ability to provide ample current flow at higher draws, when comparing the various AA NiMH's) of the
R123, and which
version you get. JSB's older
protected cells, have limited ability to supply higher amounts of current quickly that you would want for these high-output, high-current drain incandescent bulbs. But they are being improved, so it depends, even with the same exact manufacturer which 'newest' version of the cells you are getting.
I think CPF member 's2k' (?) was selling some unprotected 3 & 3.7v R123's while JSB was out of stock on his protected versions of these. IIRC the current highest capacity unprotected R123's are at a labeled (not sure how much they actually test out to for
capacity under higher amp loads) at 650ma. A P91 draws 2.35amps using CR123's, according to Brock's data, so an 650ma R123 would be discharging at roughly 4C. Given that 2400ma LG 18650's are more than twice the size of the R123's, you hardly expect the R123's to do better than the LG 18650's at 2400ma, would you???
See 2nd chart on Brock's page
Discharge graphs of LG 2400ma 18650, as provided by Tweek:
http://www.candlepowerforums.com/ubbthreads/showthreaded.php?Cat=&Number=721157
Take a look at SilverFox's testing of various Lithium primary CR123A cells. At a load of 1amp, most are sagging in voltage down to about 2.5v. At 2amp loads the sag is even worse, down to about 2.25v. A bulb that draws 2+amps, will at very best, only be supplied with 4.5v in a 2 x 123 light, 6.75v in a 3 x123; using CR123A's. This means that in order for SF P91 LA to burn at anything less than a yellow color, the bulb inside the P91 must be of a design to run at around 6v, a 9v bulb would barely even light up!
123 Battery Shoot Out
How much do R123, protected vs. unprotected (and again it depends on which 'newest' improved version you get); sag in voltage under 2amp loads. Has SilverFox done a test on these?
