Most genuine Rolex watches have an automatic or manual movement, which means they do not run on battery power. Automatic movements self-wind when worn or put in a watch winder. A few Rolex watches, including the Cellini style, run on battery power. If you have a battery-powered Rolex that is not a Cellini, you may have a counterfeit Rolex watch. If you know your Rolex is authentic, you must be careful and precise when changing the watch battery so you do not damage the inner workings of the watch.

Turn your Rolex face down on a lint-free cloth so you do not scratch the face. You do not want lint getting inside your watch. Your Rolex will either have a snap back, where the case back pops open, or a screw back, which twists off. If you see small grooves around the outside of the watch case back, you have a screw back, otherwise the case is a snap back.

If you have a snap back, insert the tip of a small screwdriver in the area where the case back meets the watch case. Gently twist the screwdriver to pop open the case back.

If you have a screw back, you need a watch case opener wrench to open the case. Adjust the prongs on the wrench to fit in three grooves around the outside of the case back. A wheel in the middle of the wrench allows you to tighten and loosen the prongs. Tighten the prongs once you have fitted them to the case back. Place the prongs in the grooves and twist the wrench to the left to unscrew the case back one full turn. Remove the case back with your fingertips.

Remove the rubber gasket from around the watch case. This gasket helps keep the case watertight. You will need to put it back before you close the case.

Locate the watch battery, a small silver disc. Note which side of the battery is facing up, because you will need to put the new battery in the exact same way. Slide the tip of your screwdriver underneath the watch battery to release it. Depending on the type of watch, the battery may be held down with screws. Use a small screwdriver to remove the screws before removing the battery.

Remove the battery from the watch with a pair of tweezers. If you did not know what type of battery your watch requires, you can get the model number off the old battery.

Put the new battery in the same place with the correct side facing up. Replace the screws if the battery is held in place with screws.

Put the rubber gasket around the outside of the watch case just as you found it when you opened the case.

Press down on the watch case back if you have a snap back. When you hear a "click" you know the watch is closed. If you have a screw back, place the case back on the watch and use your watch case opener wrench to tighten the back onto the case. Turn the wrench to the right to tighten the case back.