lol... yea... don't do that. UNLESS:
here's the approximate procedure for using RCR123s at 2.5+amp. (which is 5-6+C BTW).
1. Charge cells to 4.35V (because who cares right?!),
2. Use cells on a P91, Enjoy for 5 minutes.
3. Throw the cells away, they are dead. Buy new cells and repeat.
Ok... here's the deal.. serious now:
You can probably get away with running a lamp like a P91 on RCR123s for a FEW cycles if all you want is a little wow factor job and don't care about replacing the cells frequently. You'll need to really respect the fact that li-ion cells become more and more dangerous as they age internally, and high current configurations will age their internals much more rapidly. An RCR123 really shouldn't be used in a "routine" cycle of anything greater than about 1 amp.
If you do the following:
1. Never use the full runtime available, don't run the cells down to where the low-volt-protection kicks em off. Use no more than the first couple minutes of runtime. I would guess that the total available runtime is less than 10 minutes on most RCR123s driving a P91. Use 2-3 minutes worth tops, then recharge. This will keep the cells within a "range" that it will incur less damage.
2. Use the light in short bursts. Nothing longer than 15 seconds at a time. This in conjunction with limiting total runtime used, will also retard the rate of internal destruction.
3. Test cell voltage coming out of light, and take note of how "out of balance" they are. With only a few minutes runtime used, they should stay relatively close, within a few hundredths. As the cells age, they will more than likely start to come more and more out of balance. Use this as an additional warning sign.
4. Charge with a nice slow charger that cuts off accurately, set charge cutoff to about 4.17V. I would personally charge cells used like this inside of a blasting box of sorts.
5. check cell voltage when cells are removed from charger, and again after a ~30 minute rest. The more voltage lost, the closer to the end of the life the cells are at.. A drop of about 0.2V (or a cell that dips down to 4.00 or lower) should not be used anymore. It's "dead" and dangerous.
I would also suggest a low-current runtime test setup... Something under 1 amp that you can do periodic runtime tests with. Like a setup that drives a 6 cell mag krypton bulb. Measure the runtime when new, and then again after every few cycles. When total runtime drops to 80% of the original test, the cells should be discarded.
Even with ALL these safety regiments in place, there is still no guarantee that the cells will not develop irregular internal aging patterns that could lead to a vent-with-flame event. And even with all these in place, I would still only expect the cell to deliver maybe 15-30 2-3 "minute" runs before it needs to be replaced.
If you were to charge like normal to 4.20V, and run till the protection kicked on in continuous fashion, I would expect the cells to be "dead" and dangerous in less than 5 cycles.
