Things You'll Need
Instructions
Unscrew the cap located on top of the brightness adjustment dial with the coin or screwdriver. A slot for this purpose is cut across the surface.
Remove the sight's dead battery and replace it with a three-volt lithium battery. Place the battery in a compartment with the positive ("+") side facing upward. Screw the cap back on securely.
Test the battery by turning the adjustment dial to any setting, apart from zero, and looking through the scope. You'll see the red dot if the battery is operational. After you've tested the battery, turn the brightness adjustment dial back to zero, shutting off the scope.