A large number of watches are powered by internal batteries. The battery will need to be changed when it can no longer power the timepiece. Timex watches use CR1620 lithium batteries, and you need to open the watch casing to replace one that is dead. You can replace the battery in your Timex watch using basic household tools, and should perform the procedure in a dry well-lit area. However, changing your Timex watch battery might affect the warranty.
Place the watch face down on a soft cloth. Slide a case knife under the back of the watch casing cover. Apply gently pressure to pry off the cover.
Push the battery from under the clasp using a pair of tweezers and pick it out of the watch casing. Try not to touch any other working parts of the timepiece.
Insert the new battery in the same position as the old one. Attach the watch casing, making sure that the O-ring is correctly positioned.
Insert a nylon die larger than the watch face in a watch case press. Insert the watch casing face down in the watch case press and secure it there. Attach a nylon die slightly smaller than the watch case cover to the press. Close the press on the watch to close the watch back.