Timex is a popular watch brand which specializes in durable athletic watches. Since athletic watches tend to have more functions than normal watches, they run out of batteries more quickly than a standard watch. Being able to replace your watch battery is important as a watch is a tool that many people come to rely on in their every day activities.

Purchase a new watch battery. The back side of a watch will often state the type of watch battery that is needed. If not, you can wait to purchase the battery until after you have opened the watch, and taken out the old one.

Open the back plate on the watch. The inner workings of the watch should be accessible through a metal plate that is secured by several tiny screws, which may be Phillips head, flat heat, or a combination of both. Use a set of jeweler' size screwdrivers to remove the screws and take off the back plate. Make sure to put the screws in a place where you will not loose them.

Take out the old battery. As soon as the back plate is removed, the old battery should be visible. It will look like a small rounded piece of metal. Unscrew any screws holding the battery in place, then take the battery out. In some watches the battery may be able to be popped out without removing any more screws beside those on the back plate.

Install the new battery. Simply push the new battery into the circular slot in the same orientation as the old one, and screw it in place the same way the old battery was.

Close the back panel. After the battery is installed, realign the back plate and screw it back in place. Make sure that the back plate is situated properly before screwing it tightly in place.