Minimum battery consumption and maximum reliability
The Nuki Door Sensor works with a 3.6V lithium battery (½ AA ER14250), which is included in your Nuki package.
To check the battery level of your Door Sensor tap on your Smart Lock and enter the lock settings. Now select "Features & Configuration" > "Manage Nuki Door Sensor".
If the battery level drops below 20%, the Nuki app reminds you to change the battery of the door sensor.
Change batteries
The battery compartment is located on the back of the Nuki Door Sensor. It is closed by the back panel of the Nuki Door Sensor, which serves as a mounting plate.
To open the battery compartment, remove the Nuki Door Sensor from the mounting plate. If the Nuki Door Sensor is already mounted, just hold it on both sides and pull the housing forward.

Minimal battery consumption
The Nuki Door Sensor and the Smart Lock work extremely energy efficient: The Nuki Door Sensor has a battery life of about 2 years.
More informations on optimized energy management:
Your Door Sensor knows two different states: Either it is in sleep mode or in active state.
Most of the time, your door sensor is in sleep mode and thus consumes hardly any energy. There is no LED signaling or Bluetooth communication in sleep mode, which results in minimal power consumption.
To reduce battery consumption, the Nuki Door Sensor is only active when a status change occurs. If the door status changes, the Nuki Door Sensor is activated. It registers the change and sends the information via Bluetooth to the Smart Lock. Afterwards, your door sensor automatically returns to the energy-saving sleep mode.