The batteries do not have to be dead for the steripen not to work. When I got home I measured the batteries and think they were down to about 2.8v or something like that. I measured them again after they had been sitting around for 3 days ant they were back up to 3.1v. As far as I am concerned, I will not be taking the steripen on another trip unless I can rig a switch to shut the batteries off completely. I have an idea, just need to see if I can execute it.