Was having the same trouble. Here's the trick. Hold the headlight in your hands, with the light facing forward and your hands cupped like you're trying to hold water in them (thumbs facing up). Now place your two thumbs on the TOP (not the sides) of the battery cover, just on either side of the switch at the front of the cover. Squeeze straight down on the cover with your thumbs, and curl your thumbs back toward you. Just a little bit of friction does it.
