Polar recommends that the batteries in its watches be replaced by professionals; however, you can save time and money by replacing the battery yourself. Replacing the battery yourself can invalidate the Polar warranty on your watch, which is why Polar strongly recommends that the watch be sent to it for battery replacement.
Use the jeweler's screwdriver to remove the four small screws located on the back face. Remove the back of the Polar watch to expose the battery.
Write down the numbers on the battery. This information will be necessary to buy a new battery. Polar have multiple models and different models require different batteries.
Insert a paperclip, or small pin, into the semicircular opening adjacent to the battery; this releases the metal battery cover. Remove the metal cover.
Place the new battery in the battery cradle and press down gently until you hear it click into place. The battery numbers should be facing up.
Replace the metal battery cover.
Replace the back face of the watch by using the jeweler's screwdriver and the 4 small screws.