armitron watches have a notoriously long shelf life. Watches made ten years ago, are still running in perfect condition. However, other versions run out of charge, after just a few years. When the watch slows down or stops working completely, that’s a clear sign that the battery should be replaced.
Pick up a watch repair kit. These kits contain the tools needed for the job including a small screwdriver and a "flat" tool known as a watch case opener for prying off the back of the watch. Then place the watch face down on a soft surface such as a towel or pillow.
Insert the watch case opener from the repair kit into the side of the watch in the gap between the back and the watch itself. Apply a small amount of pressure to loosen the backing and get it to come off. You may also notice a small notch in the back to the Amitron watch, which shows you where to place the tool.
Pull off the rubber gasket on top of the battery. Place the flat tool against the clip that holds the battery in place and remove the clip. Flip the watch upside down and let the battery fall out.
Place the new battery in the back of the watch and press down firmly to ensure it slides into place. Then, put the clip back in and add the rubber gasket before attaching the back of the watch. Set the time and ensure the watch is working.