My batteries are Rayovac NiMH rechargables. The light holds two AA size batteries. It hasn't come in yet. I'll have to actually leave it on and carry it around with me to check the run time. I've used a Cateye EL-300 before with them, and they would last over 10-12 hours without losing power. I got the NiMH so I could keep recharging them after one or two uses. I haven't let them run completely down yet.