Key fob batteries

What to check before you buy

• Read the code on the old battery, or look it up in your owner's manual, before you buy.
• Put the new battery in the same way round as the old one: take a photo before you remove it.
• Keep coin batteries, new and used, away from children.
• If the fob still does not work after a battery change, see your owner's manual or a dealer.

How to use it

1. Find the release button or the slot on the fob.
2. Open the case gently with a coin or a small flat tool.
3. Swap the battery, the same way round as the old one.
4. Close the case and test the buttons near the car.

Good to know

• Most key fobs run on a small lithium coin battery; the CR2032 and CR2025 are two of the most common sizes.^1,2,3
• The battery code is printed on the old battery, and the owner's manual usually names the battery your fob takes.^1,3,4,5
• A CR2032 and a CR2025 are both 20 mm across, but the CR2032 is 3.2 mm thick and the CR2025 is 2.5 mm thick; the first two digits give the diameter in millimeters and the last two the thickness in tenths of a millimeter.^6,7,8,9
• Put the new battery in the same way round as the old one, with the + side where the old battery's + side was.^1,2,3
• Keep coin batteries away from children: a swallowed coin battery can cause serious injury or death in as little as two hours.^10,11,12
• If you think a child has swallowed a coin battery, go to the emergency room right away and call the National Battery Ingestion Hotline at 800-498-8666.^10,11
• Many push-button-start cars can still be started with a weak fob if you hold it against the start button or put it in a marked spot; your owner's manual shows where.^13,14,15,16
• Most fobs keep working after a battery change without being reprogrammed; in rare cases one needs a dealer.^1,3,16

How we checked this page

Checked on October 17, 2026. We kept a fact only when two independent sources agree, and each one is numbered to its sources below. We never write a price: the listings come straight from eBay and show what sellers ask. This page was written with an AI assistant and checked against the sources below.

Sources

1. How to change a key fob battery (Joe Weber, 2025), Batteries Plus
2. Dead key fob? Here's how to fix it fast (Matt Hill, 2025), AAA
3. How to change the battery in a key fob (Chris Tonn), Reader's Digest
4. CX-5 owner's manual (2025): key battery replacement, Mazda
5. 2020 Chevrolet Silverado owner's manual, Chevrolet (General Motors)
6. CR2032 lithium coin battery, Panasonic
7. CR2032 product datasheet, Energizer
8. Mignon, R6, CR2032: are you able to decipher battery names? (Martin Jungfer, 2025), Digitec Galaxus
9. Quick coin battery guide (Nate Eastland), Digilent
10. Reese's Law leads to new federal mandatory safety standard (2023), CPSC
11. Button batteries, National Capital Poison Center
12. Smart key battery replacement (owner's manual), Kia
13. 2021 CR-V push button start, Honda
14. Focus quick reference guide, Ford
15. Your car's key fob may have hidden features (Mike Monticello), Consumer Reports
16. Key fob replacement (Chris Hardesty, 2025), Kelley Blue Book