how to change fire alarm battery

Kidde recommends replacing the batteries in all of your alarms at least once a year, or any time the unit indicates that the battery is low. The general rule is to replace the battery twice a year: once when you switch to daylight savings time, and once when you switch back to daylight standard time.

When the battery requires replacement, the alarm will sound with a short beep or chirp. At this time, you must remove the old battery and replace it with a fresh battery of similar brand. Here's how to change the battery in your smoke detector:

To replace batteries in models with rear-loading batteries

If your tamper-resist pin is engaged, it will need to be removed. If you have a tamper-resist locking tab, it will need to be pushed in with a screwdriver before you can twist the alarm and remove it from the bracket.

Remove the alarm from the mounting plate by twisting it in the direction of the Off arrow on the plate.
If you have an AC Hardwired (Interconnected) alarm, you will need to remove the Quick Connect wire harness from the back of the alarm by squeezing the plastic prongs and pulling the wire harness out of the alarm.
After the alarm has been removed, open the battery compartment door.
Insert the battery by first pressing the red battery reminder finger down into compartment. NOTE: Be sure the battery's connectors (+ and -) line up with the metal plates inside the battery compartment.
Once the battery is installed, close the compartment door and press the test button to make sure the unit operates on battery only before installing the unit back on the ceiling. If the unit does not sound, re-open the battery compartment door to make sure the red reminder pins are pressed down and that the batteries are lined up properly.
If you have an AC Hardwired (Interconnected) alarm, you will then need to re-connect the Quick Connect wire harness to the back of the alarm before installing the unit back on the mounting bracket. Line up the Quick Connect wire harness holes with the pins on the back of the alarm. Then, squeeze the wire harness' plastic prongs together and push the wire harness into the unit until it snaps into place.
Re-install the alarm onto the mounting bracket by twisting it in the direction of the On arrow on the plate.

For detailed instructions and diagrams, consult your user's manual.

To replace batteries in models with front-loading batteries

Open the battery compartment door by pressing down on the battery compartment door, then release to allow the door to pop open. Pull the battery straight out of the compartment.
Insert the battery into the compartment. Make sure the battery's connectors (+ -) are facing out. Line up the plus (+) and minus (-) connectors with the yellow label on the bottom of the battery compartment.
Once the battery is inserted, press down on the battery compartment door until it snaps into the closed position. If the battery door slides open, make sure it's open all the way before removing and installing the new battery(ies). For models using AA batteries, make sure the contacts are not facing the same direction.
NOTE: A missing or improperly installed battery will prevent the battery compartment from closing.
Press the test button to make sure the unit operates on battery only before installing the unit back on the ceiling. If the unit does not sound, re-open the battery compartment door to make sure that the batteries are lined up properly.