I tried the cheap Ultrafire 14500 pair I bought a few months back and still had sealed in the package. Very bright. Excited a couple hours then it dawned on me, not practical at all without a lower output mode for normal use.
I started a new thread to discuss best emitter etc. using the 14500 NEW THREAD
I was thinking about using unprotected cells, and decided not to so, no need for the lower voltage option.