Swapping E1L head with 2 cell model to use RCR123 ?

Swapping the KX1 head for the KX2 head should make it possible to use the slightly more potent rechargeable cells in the one cell light, am I correct in this?
This is the CREE model.
I realize there would probably be some loss of runtime,
but I would have slightly more volts to compensate and the convienience of rechargable cells if this would work.
Would this be worth the effort?
Has anyone done this and know what the runtime might be ?
I am partial to the 1 cell lights for size and weight.

Have you tried an RCR123 with the E1L head? If you have a fairly high vf LED in the E1L you might be able to run it at 4.2 volts. It will likely run in overdrive until the voltage drops enough to run in regulation. Not sure this would work, but if tried once it would not ruin the LED, and if you got some serious flickering, or extreme heat you could back off. You could also use a DMM to measure the current from the battery, and compare to the stock CR123 current.

The E2L head, utilizing a buck circuit, would run ok with one RCR123, with probable fairly fast drop off in output, again depending on the vf of the LED. If very low vf it will run in regulation for awhile until voltage drops.

You could have the sense resistor changed in the E1L so current to the LED is increased. This would raise the vf of the LED and make running an RCR123 more practical.

Bill

I am pretty sure the rating I saw for the single cell head is 3v so it is for non recharge cells only, so I thought the swap would put it up to 6v and allow the RCR123 's use. Just don't know if the drop in runtime was worth the savings on batteries. I think I saw RCR123 batts at 3.7? volts or 4.2v?