If the battery with one bar icon flashes on the display while the thermometer is in use, the battery is low. You will still be able to measure a few more times at this point, but you should have a spare battery ready.
You will also be able to see the battery of the thermometer in the app under the menu > Settings > Thermometer, where it will be shown if the battery is Full, Sufficient or Low.
You should change the battery if after switching on the thermometer, the “battery flat” indicator appears on the display (an empty battery icon). At this point, you must insert a new battery before you can take any temperature measurements.
The thermometer is equipped with a CR2032 lithium battery.
To change the battery, first unlock the battery cover by turning it past the marker to the left, and then lift the cover off. Remove the old battery and insert a new one (CR2032) with the plus (+) symbol facing up. Place the cover back on the battery compartment and lock it in place.
After changing the battery, the thermometer must be paired with the Natural Cycles app again before you are able to continue measuring. To do this, open the app and go to the menu > Settings > Thermometer, and follow the steps to pair your thermometer.
Measurement values stored on the device are still saved when the battery is changed.
If needed, you can also find these instructions along with illustrations in the user manual that came with your thermometer.