RuuviTag has an excellent power consumption profile. When using the sensor with the included CR2477 battery, the beacon can run up to several years under standard use and operating conditions.
Important notice: If operating conditions exceed -20°C to +65°C temperature range, a battery designed to be used within extended temperature range must be used.
CR2477 sized battery can easily be replaced by the user. Pop the empty battery out from the battery holder and replace it with a new compatible 3V coin cell type battery.
See the video how to change the battery here.