The RECHARGEABLE battery needs to be changed every few years OR when the light is not bright or doesn't shine as long as before.
1) Hold the light with one hand and the lens with the other hand. Using 1/4-turn motion, separate the two components.
2) Turn the light upside down and remove the screws
3) Lift cover carefully. Remove old battery carefully without disturbing the wiring. Replace with new battery. Dispose of old battery properly (not in landfill). Replace cover by realigning screw holes. Install screws. Replace light on lens (reverse of step 1) by aligning tabs on lens with slots on light cover and giving a 1/4-turn