Our sensors have a CR2477 battery installed, which theoretically lasts about 4 years. In practice, however, the battery life will be somewhat shorter and depends on many factors, such as the environmental temperature. To be on the safe side we talk about a battery life of 2 years +. As a short explanation: the battery life depends largely on the temperature. At very cold temperatures, the battery life is shortened, and at really warm temperatures, the electronics consume slightly more power than at room temperature