The Garmin Forerunner 305 heart rate monitor is a fitness tool that features a GPS receiver, data collection software and programmable courses. Many heart monitors require you to strap the units around your chest for accurate heartbeat measurement. The Forerunner 305 looks similar to a sports watch and straps to your wrist instead. The unit measures heart rate by counting the pulse on your wrist. This Garmin monitor comes with a replaceable CR2032 battery. If the battery fails to charge on your unit, replacing it takes just a few minutes.
Flip the monitor over so the display is facing downward.
Place a coin, such as a dime, into the recessed slot on the circular battery cover. The cover sits on the backside of the monitor.
Turn the coin counterclockwise until the cover stops moving.
Tap the back of the unit against the palm of your hand to dislodge the cover and battery. Follow the instructions on the replacement battery for proper disposal of the old battery.
Insert the new battery with the “+” marking up. Take care not to touch the leads on the battery. Hold it with your fingertips on the side. Lower the battery into the empty compartment.
Replace the battery cover. Insert the coin into the slot and turn clockwise until the cover is secure.
Replacing the battery may require you to reset the functions on the monitor unit.