You can replace most key fob batteries yourself in under five minutes
A dead key fob battery is one of the easiest car problems to fix without a mechanic. Most fobs use a standard coin-cell battery — usually CR2032, CR2025, or CR2016 — that you can buy at any drugstore or supermarket for a few dollars. The replacement takes longer to find the battery aisle than to swap it out.
The hardest part is opening the fob itself, and even that is straightforward once you know where to look. You do not need tools beyond what you probably have at home, and you cannot damage anything by doing this wrong — the battery straightforward will not work if you install it backwards, and you can flip it and try again.
Key Takeaways
- Most car key fob batteries are CR2032, CR2025, or CR2016 coin cells, sold at pharmacies and grocery stores for under five dollars.
- Open the fob by finding the seam or slot on its edge and gently prying with a coin, butter knife, or flathead screwdriver — do not force it.
- Note which side of the battery faces outward before you remove it, then install the new battery the same way.
- If the fob still does not work after the battery swap, the problem is likely the fob itself, not the battery, and a dealer can test it.
Find out what battery your fob uses
The easiest way is to open the fob and look at the old battery. The battery type is printed on the flat side — you will see something like CR2032 or CR2025. Write it down or take a photo with your phone.
If you want to know before you open it, check your car's owner manual — many list the battery type in the key fob section. You can also call your car's dealer with your vehicle identification number (VIN), and they will tell you. Some fob manufacturers print the type on the back of the fob itself, though not all do.
Open the fob without breaking it
Look at the edge of your fob for a small seam or slot. This is usually on one of the long sides, though some fobs have it on the top or bottom. The seam is where the two halves of the plastic case meet.
Slide a coin (a penny or dime works well), a butter knife, or a flathead screwdriver into the seam and gently twist or pry. You are not trying to force the halves apart — you are just creating enough space for them to separate. If it does not budge after light pressure, try a different spot along the seam. Some fobs have a small notch or indent that marks the right spot to pry.
Once the halves start to separate, you can usually pull them apart by hand. Be gentle — the plastic clips that hold the case together are small and can break if you yank too hard. If the fob has a circuit board and button pad, they may fall out when you open it, and that is normal. Just set them aside on a clean surface so you do not lose them.
Remove the old battery and note its position
Before you touch the battery, look at how it sits in the fob. Is the flat side facing up or down? The positive side (marked with a +) usually faces up, but not always. Take a mental note or a quick photo — you will install the new battery the same way.
Gently pry the battery out with your fingernail or the edge of a coin. It should come out easily. If it is stuck, a tiny dab of moisture on your fingertip can help you grip it better. Do not use force — if it will not budge, you may have the wrong angle, so try from a different edge.
Install the new battery and reassemble
Place the new battery into the fob with the same side facing the same direction as the old one. If the positive side faced up before, the positive side of the new battery should face up. The battery should sit flat and snug in its slot.
Close the fob by pressing the two halves together. You should hear or feel a small click as the clips snap back into place. If the circuit board or button pad fell out, make sure they are back in the fob before you close it. Test the fob by pressing each button — the lights should come on, and the car should lock and unlock.
What to do if the fob still does not work
If the fob does not respond after the battery swap, the battery is probably not the problem. The circuit board inside may be damaged, the buttons may be worn out, or the fob may have gotten wet at some point. These are not things you can fix at home.
Take the fob to your car's dealer or a locksmith who makes car keys. They can test it to confirm whether it is the fob or something else. If the fob is broken, they can order a replacement or reprogram a used one. The cost varies — some dealers charge $50 to $150 for a new fob, though prices differ by make and model.
Where to buy the right battery
Coin-cell batteries are sold at pharmacies (CVS, Walgreens), grocery stores, hardware stores, and online retailers. A single battery usually costs $2 to $5. Some stores sell them in multipacks if you want to keep spares on hand.
Make sure you buy the exact type your fob uses — CR2032, CR2025, or CR2016 are the most common, but they are not interchangeable. If you are not sure which one, bring the old battery with you to the store and match it, or ask a store employee to help you find the right one.
Frequently Asked Questions
Can I use a rechargeable battery in my key fob?
Rechargeable coin cells exist, but most car key fobs are not designed for them. Rechargeable batteries have a different voltage curve than disposable ones, and your fob may not work properly or may drain the battery faster. Stick with the standard disposable type your fob came with.
What if I install the battery backwards?
The fob straightforward will not work. The buttons will not respond, and the lights will not come on. You will not damage anything — just open the fob again, flip the battery around, and close it. No harm done.
How long does a key fob battery last?
Most fob batteries last three to four years with normal use, though heavy use can drain them faster. If you use your fob dozens of times a day, you may need a new battery sooner. There is no way to predict exactly when it will die — you will just notice the buttons stop working.
Do I need to reprogram my fob after changing the battery?
No. The battery change does not affect the programming. Your fob should work exactly as it did before, as long as the new battery is the correct type and installed the right way.
What should I do with the old battery?
Coin-cell batteries contain small amounts of lithium and should not go in the trash. Take the old battery to a pharmacy, electronics store, or hazardous waste collection site in your area. Many retailers that sell batteries also take old ones back for free.