Follow The Signs
When the battery on your Polar heart rate monitor begins to weaken, your wrist display will show you some indicators. The lit low-battery indicator activates when 10 to 15 percent of the battery function remains. When this occurs, your watch automatically turns off the backlight and sound functions. If you see the indicator in cold weather, but then it disappears when you return to room-temperature, your battery does not need replacing. Before you remove the battery, transfer your exercise data online through the Polar website.
The model of the Polar monitor will affect how you change the battery. Look at the back of the watch. If you see a silver covering held on by little screws, you need a small, Philips screwdriver. Loosen all four screws and remove the back. Instead of using the metal screwdriver to remove the battery, find a plastic tool, or a wooden toothpick or popsicle stick. Place the tool under the battery and gently press up to pop out the battery. Replace it with a new battery and position the positive, plus sign, side of it facing up. Align the small heart on the underside of the metal covering with the metal contact next to the battery to properly position the covering. Tighten the little screws and your battery is replaced.
The newer Polar monitors and chest straps have plastic coverings over their batteries. The coverings have a small slot that fits the side of a coin. Insert the coin and twist the covering to the "open" position. Use a plastic or wood, flat-head tool or popsicle stick that fits underneath the battery. Press up and pop out the battery. Replace the battery on the wrist monitor and face the positive side out. Replace the chest strap battery by putting the battery into the plastic cover with the positive side facing the cover. Also, replace the sealing ring on the chest strap if you have a new one. You can purchase the batteries and rings together from Polar. Return the coverings to their proper places and twist the coin until the covering is in the "closed" position.
Voiding The Warranty
A Polar monitor comes with a 2-year warranty that guarantees the device will be free of defects. If you purchased the monitor second-hand, the warranty is not valid. This warranty also does not cover the battery. The challenge here is in regards to the older Polar models that have to be opened with a screwdriver. The warranty is voided when you open the back, but hopefully, you're already past the 2-year warranty period by the time you need to change the battery. If not, follow Polar's guidelines on where to send the watch for battery replacement.