[ QUOTE ]
Lurker said:
This may not be what you are looking for, but I believe the EverLED is supposed to work on one cell, although not necessarily at max brightness.
[/ QUOTE ]
I have 2 Everled drop ins.
They do lose brightness and heat at anything less than 3.5 volts.
At 1.5 volts, They make you wonder why you paid $40 a piece for them.
A step-up dc-dc inverter, and several t5 leds may be the better answer.
Good luck.