Open the key fob without damaging it
Most key fobs split into two plastic halves held together by a small slot or seam. Look for a thin line running around the edge of the fob — that is where the two halves meet. Insert a flat tool like a butter knife, flathead screwdriver, or coin into that seam and gently twist to pry the halves apart. Do not force it; if it does not budge after light pressure, try a different spot along the seam.
Some fobs have a small button or latch on the side that you press to release the battery compartment. Check the back of your fob for any markings or arrows pointing to this release point. If your fob has this type, press the button and the compartment should slide out or pop open. Once the fob is open, you will see the battery sitting in a small metal or plastic holder.
Key Takeaways
- Most key fobs use a CR2032, CR2025, or CR2016 battery — check your old battery or the fob's manual to know which size you need before you buy a replacement.
- Note which side of the battery faces up (the positive or negative side) before you remove it, so you can install the new one the same way.
- Pry the fob open gently along the seam using a flat tool, or look for a release button on the side if your fob has one.
- Clean the metal contacts inside the fob with a dry cloth or cotton swab before closing it back up, because dirt can prevent the battery from making good contact.
Identify and remove the old battery
Look at the battery sitting in the fob. The top side (marked with a + or —) tells you the polarity. Most key fob batteries are coin-shaped and silver in color. The most common sizes are CR2032 (the largest), CR2025 (slightly thinner), and CR2016 (the thinnest). Write down or photograph the battery type before you remove it, because you will need to buy the exact same size.
Gently lift the battery out of its holder. If it is stuck, slide a fingernail or plastic tool under the edge and ease it up. Do not use a metal tool that might scratch the battery holder or create a spark. Once the battery is out, set it aside and look at which side was facing up — this matters when you put the new battery in.
Buy the correct replacement battery
Take the old battery or the size number you wrote down to any pharmacy, grocery store, hardware store, or electronics retailer. Coin cell batteries like CR2032 are inexpensive and widely available — you will find them near the checkout counter or in the battery aisle. A single battery usually costs between one and three dollars. Buy one battery, or buy a small pack if you want spares on hand.
Do not assume all coin batteries are the same. CR2032, CR2025, and CR2016 look nearly identical but are different thicknesses, and using the wrong size can prevent the battery from making contact with the metal terminals inside your fob. If you are unsure which one your fob uses, bring the fob itself to the store and ask a staff member to help you match it.
Install the new battery correctly
Before you place the new battery in the holder, look at the metal contacts inside the fob. If they look dirty or corroded (dark or discolored), wipe them gently with a dry cloth or a cotton swab. Clean contacts help the battery work better and last longer.
Now insert the new battery into the holder with the same side facing up as the old battery was. The positive side (marked with a +) usually faces up, but check the markings inside the fob — there may be a small + or — printed on the plastic to show you which way it goes. Press the battery down gently until it sits flat and snaps into place. You should hear or feel a small click.
Close the fob and test it
Align the two halves of the fob so the seam lines up evenly. Press them together firmly until you hear a click or feel them snap shut. Do not force them — they should come together smoothly. If they do not close all the way, the battery may be sitting at an angle. Open the fob again, reseat the battery, and try closing it once more.
Test the fob by pressing each button while standing near your car. You should see the car's lights flash or hear the locks click. If nothing happens, open the fob again and check that the battery is sitting flat and making contact with both metal terminals. If the fob still does not work after you have reseated the battery, the battery itself may be defective — try a fresh one from a different package or store.
What to do if the fob still does not work
If a new battery does not fix the problem, the issue is usually inside the fob itself. Water damage, a cracked circuit board, or worn-out buttons can all prevent a fob from working even with a fresh battery. Open the fob again and look for any visible damage — cracks, corrosion, or moisture inside the plastic case.
If the fob looks dry and intact but still does not respond, try cleaning the rubber button pad and the metal contacts on the circuit board with a dry cotton swab. Sometimes dirt or oxidation builds up over time and blocks the electrical connection. If cleaning does not help, you will likely need a replacement fob from your car's manufacturer or a locksmith who programs fobs for your vehicle model.
Frequently Asked Questions
How long does a key fob battery last?
Most key fob batteries last three to four years with normal use. If you use your fob heavily — pressing the buttons many times a day — the battery may wear out in two to three years. You will notice the fob working from a shorter distance before the battery dies completely.
Can I use a different battery size if I cannot find the exact one?
No. CR2032, CR2025, and CR2016 are different thicknesses, and using the wrong size means the battery will not make proper contact with the metal terminals. Your fob will not work, or will work only intermittently. Always match the size number on your old battery.
Is it safe to replace the battery myself?
Yes. Key fob batteries are small, low-voltage, and safe to handle with your bare hands. You do not need special tools or training. Just avoid touching the metal contacts with dirty fingers, and do not force the fob open if it is stuck.
What should I do with the old battery?
Most coin cell batteries can go in the regular trash, but some communities prefer them recycled. Check your local waste management website or ask at a pharmacy or electronics store — many accept old batteries for free recycling.
Why is my new battery not working even though it is the right size?
The battery may be defective, or the metal contacts inside the fob may be dirty or corroded. Open the fob again, wipe the contacts with a dry cloth, reseat the battery, and test it. If it still does not work, try a battery from a different package or brand.