The battery life of a fire detector varies greatly from one device to another. It also depends on the conditions in which the detector is used (ambient temperature, frequency of testing, frequency of alarms, etc.). Roughly speaking, you can expect the following battery life:
- 9 volt battery detectors: the battery needs to be replaced approximately once a year.
- AA battery detector: the battery need to be replaced approximately every two to three years.
- Lithium battery detectors: the batteries will last approximately for 5 to 10 years, as indicated on the product page and packaging.
- Wireless fire detectors with 9V and AA batteries: replace the 9V battery (for the alarm) approximately every year, replace the AA batteries (for the coupling) approximately every 2 to 3 years.
- Wireless fire detectors with lithium battery: the battery will l ast 10 years, as indicated on the product page and packaging.
The above are only guidelines. Regardless of the life span specified by the manufacturer, you MUST replace the battery (or the alarm itself if the battery is built-in) immediately when the device begins to "beep" (the "low battery warning signal").