what batteries do smoke detectors use

Smoke detectors can use different types of batteries, but the most common ones are 9V and AA batteries. In the past, 9V batteries were the most popular choice, but nowadays, it is more common to see two or three AA batteries in smoke detectors. AA batteries have about three times as much energy as a 9V battery, which makes them a better choice. Smoke detectors that use 10-year sealed batteries are also available. These alarms contain lithium batteries that last for the life of the alarm, eliminating the need for battery replacements. If a smoke detector starts to chirp, it is an indication that the battery is dying, and it should be replaced immediately. The batteries in smoke detectors should be replaced every six months.