Open the detector and remove the old battery
Most Kidde carbon monoxide detectors use a 9-volt battery held in a plastic clip inside the unit. To access it, look for a seam or latch on the front or side of the detector — usually marked with an arrow or the word "open". Press or slide this latch and the cover will pop off or swing open.
Once the cover is open, you will see the 9V battery connected to a clip. Grasp the battery firmly and pull it straight out of the clip. The connector will release easily. Set the old battery aside — do not throw it away yet, as you may need to test the detector after installation.
Install the new 9-volt battery
Take a fresh 9-volt battery and align the terminals (the metal connectors on top) with the clip inside the detector. The clip is designed to fit only one way, so if it does not slide in smoothly, flip the battery and try again. Push the battery into the clip until you hear or feel a click.
The detector should beep once or twice when ready after the battery makes contact. This beep confirms the battery is installed correctly and the unit has power. If you hear no sound, remove the battery, check that the terminals are clean and free of corrosion, and try again.
Key Takeaways
- Kidde detectors use a standard 9-volt battery held in a clip inside the unit, accessible by opening the front cover.
- Pull the old battery straight out of the clip, then slide the new battery in until it clicks into place.
- The detector will beep once or twice when the new battery makes contact, confirming it is installed correctly.
- Close the cover fully and test the detector using its test button to may support it is working after battery replacement.
- Replace the battery once per year or whenever the detector chirps at regular intervals, which signals low battery.
Close the cover and test the detector
Snap or slide the cover back into place until it sits flush with the body of the detector. You should hear or feel it lock. Do not force it — if the cover does not close smoothly, the battery may not be seated correctly, and you should open it again and reseat the battery.
Once the cover is closed, press and hold the test button on the front of the detector for three to five seconds. The alarm should sound loudly — a loud beep or horn sound. If it does, the detector is working and the battery is good. If you hear nothing or only a weak sound, remove the battery again and check the terminals for dirt or corrosion.
When to replace the battery
Kidde detectors signal a low battery by chirping once every 30 to 60 seconds — a single short beep, not the full alarm sound. This chirp will continue until you replace the battery. Do not ignore it; a detector with a low battery cannot protect you.
Even if your detector does not chirp, replace the battery once per year. Many people do this on the same day they change the batteries in their smoke detectors, or on a date they will remember — such as when clocks change for daylight saving time. Write the installation date on the battery itself with a permanent marker so you know when it was last changed.
Troubleshooting a detector that will not beep after battery replacement
If the detector does not beep when you press the test button after installing a new battery, first check that the battery is fully seated in the clip. Remove it, look at the terminals on both the battery and the clip, and wipe them clean with a dry cloth. Corrosion or dust can prevent contact.
If the terminals are clean and the battery still does not work, try a different new battery — the first one may be defective. If a second battery also fails to produce a beep, the detector itself may have reached the end of its life. Kidde detectors typically last five to seven years. Check the date printed on the back or bottom of the unit; if it is more than seven years old, replacement of the entire detector is safer than continued use.
What to do with the old battery
Do not throw a 9-volt battery in the trash. These batteries contain materials that can harm the environment if they end up in a landfill. Instead, take the old battery to a battery recycling program. Many electronics retailers, including Best Buy, accept 9V batteries for free recycling at the customer service desk.
You can also search for a local recycling center using the Earth911 recycling search tool online — enter your zip code and "9 volt battery" to find drop-off locations near you. Some municipal hazardous waste collection events also accept batteries. Call your local solid waste management office to ask when the next collection day is scheduled.
Frequently Asked Questions
Can I use a different type of battery in my Kidde detector?
No. Kidde carbon monoxide detectors are designed for a 9-volt battery only. Using a different size or type of battery will not fit the clip and will not power the detector. Always use a standard 9V battery from a reputable brand.
How long does a 9-volt battery last in a carbon monoxide detector?
A fresh 9-volt battery typically lasts one year in a Kidde detector under normal conditions. The detector will chirp when the battery is low, usually a few weeks before it is completely dead. Replace it as soon as you hear the chirp.
What if my detector chirps even after I put in a new battery?
If the chirping continues after battery replacement, the detector may be signaling a different problem — such as a sensor malfunction or end of life. Consult the manual that came with your detector, or contact Kidde customer service. The detector may need to be replaced rather than repaired.
Is it safe to use my detector while the battery is low?
No. A detector with a low battery cannot reliably detect carbon monoxide. Replace the battery as soon as you hear the chirp. Do not wait until the battery is completely dead.
Do I need to turn off the detector before replacing the battery?
No. Removing and replacing the battery takes only a few seconds, and the detector will not lose its ability to function during that brief time. You do not need to flip any switches or reset anything — straightforward remove the old battery and install the new one.