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At the end of the working life of the product Polar encourages you to minimize possible effects of waste on the environment and human health by following local waste disposal regulations and, where possible, utilizing separate collection of electronic devices. Do not dispose of this product as unsorted municipal waste.

Keep the batteries away from children. If swallowed, contact a doctor immediately. Batteries should be disposed of properly according to local regulations.

Charging A300 battery

The A300 has an internal, rechargeable battery. Rechargeable batteries have a limited number of charge cycles. You can charge and discharge the battery over 300 times before a notable decrease in its capacity. The number of charge cycles also varies according to use and operating conditions.

Do not charge the battery in temperatures under 0°C or when the A300 is wet.

The USB connector is in the device, which makes recharging simple - no long and clumsy cables needed. Just plug your A300 straight to your computer. However, we deliver a standard USB cable along with the A300, so if you prefer using it, please do.

You can charge the battery via a wall outlet. When charging via a wall outlet, use a USB power adapter (not included in the product set). If you use a USB power adapter, make sure that the adapter is marked with "output 5Vdc" and that it provides a minimum of 500mA. Only use an adequately safety approved USB power adapter (marked with "LPS", "Limited Power Supply", "UL listed" or “CE”).

Do not charge Polar products with a 9 volt charger. Using a 9 volt charger can damage your Polar product.

  1. Plug your A300 to your computer's USB port either directly (A) or with the USB cable (B). Make sure the cable is right way up - the USB symbols on the back cover of the device and on the cable are next to each other. Check that the A300 is dry before connecting it to the computer. If the battery is completely empty, it takes a couple of minutes for the charging to start.
  2. Charging appears on the display.
  3. When A300 is fully charged, Battery full. Unplug. is displayed.

Don't leave the battery fully discharged for a long period of time or keep it fully charged all the time, because it may affect the battery life time.

Battery Operating Time

The battery operating time is up to 26 days with 24/7 activity tracking and 1h/day training. The operating time depends on many factors, such as the temperature of the environment in which you use your A300, the features you use, and battery aging. The operating time is significantly reduced in temperatures well below freezing. Wearing the A300 under your overcoat helps to keep it warmer and to increase the operating time.

Low Battery Notifications

Battery low
The battery charge is low. It is too low for recording a training session. It is recommended to charge A300.
Battery low. Charge.
The charge has dropped to a critical level. Charge your A300 as soon as possible. The charge is too low for recording a training session. A new training session cannot be started before charging A300.

When the display is blank, the battery is empty and A300 has gone to sleep mode. Charge your A300. If the battery is totally drained, it may take a while for the charging animation to appear on the display.

Changing Heart Rate Sensor Battery

To change the battery of the heart rate sensor yourself, carefully follow the instructions below:

When changing the battery, make sure the sealing ring is not damaged, in which case you should replace it with a new one. You can purchase the sealing ring/battery kits at well-equipped Polar retailers and authorized Polar Services. In the USA and Canada, the additional sealing rings are available at authorized Polar Service Centers. In the USA the sealing ring/battery kits are also available at

When handling a new, fully charged battery, avoid clasp-like contact, i.e. simultaneously from both sides, with metal or electrically conducting tools, like tweezers. This may short circuit the battery, causing it to discharge more rapidly. Typically, short circuiting does not damage the battery, but it may decrease the capacity and the lifetime of the battery.

  1. Using a coin, open the battery cover by turning it counterclockwise to OPEN.
  2. Insert the battery (CR 2025) inside the cover with the positive (+) side against the cover. Make sure the sealing ring is in the groove to ensure water resistance.
  3. Press the cover back into the connector.
  4. Use the coin to turn the cover clockwise to CLOSE.

Danger of explosion if the battery is replaced with wrong type.