Most key fob batteries are coin-cell replacements you can swap yourself
A dead key fob battery is one of the easiest car maintenance tasks to handle at home. The battery inside is almost always a standard coin-cell type—usually CR2032, CR2025, or CR2016—that costs $3 to $8 and takes five minutes to replace. You do not need tools beyond what you already have in a kitchen drawer, and you do not need to visit a dealer or locksmith unless your fob has a different design.
The hardest part is usually opening the fob itself. Most fobs have a seam you can pry apart with a flat object, though some slide open or have a screw hidden under a sticker. Once you know how your fob opens, the battery swap is straightforward.
Key Takeaways
- Most key fob batteries are coin-cell types (CR2032, CR2025, or CR2016) that you can buy at any pharmacy, grocery store, or hardware store for under $10.
- Look for a seam or slot on the edge of your fob and use a flat tool—a coin, butter knife, or flathead screwdriver—to gently pry or slide it open.
- Note which side of the battery faces up before you remove it, then drop the new battery in the same way and close the fob.
- If your fob has a screw, a small Phillips screwdriver is all you need; if it slides open, push from the side marked with an arrow.
Identify your fob type and find the battery size
Before you buy a replacement battery, you need to know what size your fob uses. The easiest way is to open the fob and look at the battery itself—the size code (CR2032, for example) is printed right on it. If your fob is dead and you cannot open it yet, check your car's manual or search online for your vehicle make, model, and year plus "key fob battery."
CR2032 is by far the most common size, used in the majority of car key fobs. CR2025 and CR2016 are thinner versions that fit in slimmer fobs. All three are available at pharmacies, grocery stores, hardware stores, and online retailers. Buy a pack of two or three—they are inexpensive and useful to have on hand.
Open the fob using the seam or slot
Most fobs have a visible seam running around the edge where the two halves meet. Slide a flat tool—a coin, butter knife, old credit card, or flathead screwdriver—into the seam and gently twist or pry. Start at one corner and work your way around. The fob will pop open with light pressure; do not force it or you may crack the plastic.
Some fobs have a small slot or notch marked with an arrow on one edge. If you see this, insert your flat tool into the slot and push or slide in the direction the arrow points. The fob will slide apart rather than pop open.
A few fobs have a small Phillips screw hidden under a sticker or rubber pad on the back. Peel back the sticker carefully, unscrew the fastener, and the fob will come apart. Keep the screw somewhere safe—you will need it to close the fob again.
Remove the old battery and note its position
Once the fob is open, you will see the battery sitting in a small compartment. Before you touch it, look at which side is facing up—the positive (+) side or the negative (−) side. The battery must go back in the same way, or the fob will not work.
Gently pry the old battery out with your fingernail or a plastic tool. Do not use a metal tool directly on the battery itself, as this can damage it. If the battery is stuck, a tiny dab of plastic-safe lubricant on the edge can help, but usually it comes out with light pressure.
Insert the new battery the same way
Drop the new battery into the compartment with the same side facing up as the old one was. It should sit flat and snug. If it does not fit or feels loose, double-check that you have the right size battery and that it is oriented correctly.
Test the fob before you close it. Press a button and listen for a click or watch for a light on the fob itself. If nothing happens, flip the battery over and try again—you may have had the polarity backwards. Once the fob works, you can close it.
Close the fob and test all buttons
If your fob pops apart, press the two halves together firmly until you hear or feel a click. Start at one corner and work your way around the seam to make sure it is fully seated. If your fob slides apart, slide the two halves together in the direction opposite to how you opened it.
If your fob has a screw, replace it now and press the sticker or rubber pad back down. Make sure the screw is tight enough that the fob does not rattle, but do not over-tighten—you can crack the plastic.
Test every button on the fob—lock, unlock, trunk, panic, or any others it has. Walk a few feet away from your car and test again to make sure the signal is reaching the vehicle. If all buttons work and the fob responds from a distance, the job is done.
What to do if the fob still does not work
If the fob does not respond after you replace the battery, the problem is usually one of three things: the battery is in backwards, the battery is the wrong size, or the fob has a deeper problem that a battery swap cannot fix.
Start by opening the fob again and flipping the battery over. If that does not work, remove the battery and look at the compartment itself. Make sure there is no corrosion (green or white crusty buildup) on the metal contacts. If you see corrosion, clean it gently with a dry cotton swab or a pencil eraser, then try a fresh battery.
If the fob still does not work after a fresh battery and clean contacts, the circuit board inside may be damaged. This is not a repair you can do at home. A locksmith or car dealer can reprogram or replace the fob, though this costs more than a battery. Before you pay for that, ask your car dealer whether your vehicle has a spare fob you can use while you decide whether to repair the original one.
Frequently Asked Questions
Can I use a different battery size if I cannot find the exact one?
No. A battery that is too thick will not fit, and one that is too thin will rattle and lose contact with the terminals. Stick to the size printed on your old battery or listed in your car manual. If your local store does not have it, order online—most arrive within two days.
How long does a key fob battery usually last?
Most key fob batteries last three to four years with normal use. If you use your fob many times a day, it may drain faster. If you use it rarely, it may last longer. There is no way to predict exactly when it will die, so keep a spare battery at home.
What should I do with the old battery?
Coin-cell batteries can be recycled at most pharmacies, electronics stores, and hazardous waste collection sites. Do not throw it in the trash. Many stores that sell batteries also accept old ones for free recycling.
Will replacing the battery erase my fob's programming?
No. The battery powers the fob, but the programming is stored in the circuit board. Swapping the battery will not change any settings or require you to reprogram the fob.
What if my fob has a built-in rechargeable battery?
Some newer fobs use rechargeable batteries instead of replaceable coin cells. If your fob has no seam or screw and the manual says "rechargeable," you cannot swap the battery yourself. Charge it using the cable that came with it, or contact your car dealer if the charging port is broken.