Few Rolex watches are battery-powered. Most Rolex watches have an automatic movement, meaning they are powered by the natural movement of the wearer's wrist. Fake Rolex watches and some genuine Rolex watches, including certain Cellini styles, have batteries.
Purchase a Rolex watch back opener set, if you do not already have one. This set is able to open and close any size of Rolex case.
Match the size of your Rolex case with the same size of grooved metal die from the tool set.
Put the metal die on the grooves on the back of the watch case.
Turn the die to remove the case.
Remove the rubber gasket, but keep it handy so you can replace it after changing the battery.
Remove the battery. You will easily spot it once the case is open. It may be held down by screws. If so, remove the screws with a small screwdriver from a hobby set.
Look at the back of the battery to see what model number it is, and buy a new battery.
Replace the battery the same way you found it. Remember to replace the screws if the battery is secured by screws.
Put the gasket back the same way you found it around the edge of the watch case.
Close the case and match the same grooved die to the outside of the case.
Twist the die to secure the back of the case.
Check to make sure the watch is running.
If you have no experience changing a watch battery, take the watch to your local jewellers, especially if this is a real Rolex.