KL1 is a buck (step down) and boost (step up) type of light. /ubbthreads/images/graemlins/smile.gif
You will get more runtime but same brightness out of it.
but from the data that i gather so far, it is most efficient to use the KL1 with 1 123 cell (or 2 AA batt)
Yeah, IIRC, the runtime goes from 1.5 hrs on one cell, to 4 hrs. on two, to 7 hours on three. Running on one cell is the least efficient-it sure fits in your pocket better, though!