Single AA or AAA LED torches are impressive enough with their 100/150 lumens output on a single 1.5 volt battery but these Cree LEDs on which they run are usually designed to run on 3 or more volts which means you usually can run them with either the AA (14500) or AAA (10440) sized lithium 3.6 volt rechargeable batteries. You can look up the specifications of the particular led to check. Doubling the voltage won’t quite double the lumen output but it WILL go close. The torch MAY get very hot. There may not be enough heat-sink to waste that heat and you may burn out the circuit, but I have successfully run my AAA and AA sized Fenix torches on them without causing them any noticeable harm. The result is a pocket torch good enough to spotlight a rabbit! You will need to buy a special charger: http://www.batteryjunction.com/10440.html
