Good question. I know the old incan version could, with its buck driver. I've used them that way for many years. Not sure what type of driver the LED version has though and if it can handle it. I would assume so. But I know in the past Surefire has limited the voltage use range in certain lights. An example would be the later LED Outdoorsman with the KX2 head, that would strobe if you tried to use two 3.7V batteries. Though I think Surefire has discontinued this practice a long time ago as it was meant to discourage people from using rechargeable batteries at the time. And this was before Surefire had developed their own.