Your key fob almost certainly uses a coin-cell battery, usually CR2032, CR2025, or CR2016
The battery type depends on your car's make and model, not on the fob's size. A small fob might hold a CR2032 (the most common), while a larger one might use a CR2025. The only reliable way to know is to open the fob and look at the battery itself — the type is printed on it — or check your owner's manual or the car manufacturer's website.
You can also call your car dealership's parts department with your vehicle identification number (VIN) and they will tell you the exact battery. Many auto parts stores (AutoZone, O'Reilly, NAPA) will also identify it for free if you bring the fob in.
Coin-cell batteries cost between $3 and $8 each at drugstores, supermarkets, and auto parts stores. They last two to four years depending on how often you use the fob.
Key Takeaways
- The battery type is printed on the battery itself once you open the fob, or listed in your owner's manual.
- CR2032 is the most common key fob battery, but CR2025 and CR2016 are also standard depending on your vehicle.
- You can replace the battery yourself in under a minute — most fobs have a slot or button that pops the case open.
- Coin-cell batteries from any drugstore or supermarket work as well as dealership batteries and cost less.
- If the fob still does not work after a fresh battery, the problem is likely the fob's circuit board or transmitter, not the battery.
How to open your key fob and see what battery it holds
Most key fobs have a small slot or seam on the edge where the two halves meet. Insert a flat tool — a coin, a flathead screwdriver, or a plastic pry tool — and gently twist or pry until the case splits. Some fobs have a small button on the back that you press to eject the battery holder.
Once the fob is open, the battery sits in a metal holder. Note which side faces up (the positive side, marked with a + symbol, usually faces toward you). Remove the old battery and look at the type stamped on it. Write down the number — CR2032, CR2025, or CR2016 — before you go to the store.
If you cannot open the fob without risk of breaking it, a dealership or car key shop can do it for you, usually for $10 to $20 plus the cost of the battery.
Where to buy the right battery and what to expect
Coin-cell batteries are sold at every pharmacy, supermarket, and drugstore in the country. CVS, Walgreens, Target, and Walmart all stock CR2032, CR2025, and CR2016 in their battery aisles. Auto parts stores (AutoZone, O'Reilly, NAPA, Advance Auto Parts) carry them as well, and some will install it for free or for a small fee.
Amazon and other online retailers sell them in bulk packs, which makes sense if you have multiple fobs or devices that use coin cells. A single battery costs $4 to $8 in a store; a pack of four costs $8 to $12 online.
Do not buy the cheapest generic brand if you can avoid it. Panasonic, Energizer, Duracell, and Maxell are reliable. The battery should be fresh — check the expiration date on the package, usually printed on the back.
Installing the new battery in your fob
Insert the new battery into the metal holder with the positive side (marked +) facing the same direction as the old one faced. Close the fob by pressing the two halves together until you hear or feel a click. Test the fob by pressing each button — the lights on your car should flash.
If the fob works, you are done. If it does not, remove the battery, wait 30 seconds, and reinsert it. Make sure it is seated all the way in the holder and the positive side is facing the right direction.
If the fob still does not work after a fresh battery, the problem is not the battery. The circuit board inside may be damaged, or the transmitter may have failed. At that point, you will need a replacement fob from the dealership or a locksmith who programs car keys.
Why your fob might stop working even with a new battery
A dead battery is the most common reason a fob stops working, but not the only one. Water damage is the second most common cause — if the fob has been dropped in water or exposed to high humidity, the circuit board inside corrodes and stops transmitting even with a fresh battery.
Physical damage from dropping or sitting on the fob can also break the internal components. If your fob has been through either of those, replacing the battery will not fix it.
A third possibility is that the car's receiver — the antenna and circuit that listens for the fob's signal — has failed. In that case, a new fob will not work either, and you will need a mechanic to diagnose the receiver.
How long a coin-cell battery lasts in a key fob
Most coin-cell batteries last two to four years in a key fob, depending on how often you use it. If you press the buttons dozens of times a day, the battery will drain faster than if you use the fob once or twice a day.
Temperature also matters. Batteries drain faster in very hot or very cold conditions. If you leave your fob in a hot car or in freezing weather for long periods, expect the battery to die sooner.
Some fobs have a low-battery indicator — a dim light or a slow response — that warns you the battery is dying. Others straightforward stop working one day. Once a battery dies, it cannot be recharged; you must replace it.
Programming a replacement fob versus replacing just the battery
If you are only replacing the battery in an existing fob, no programming is needed. The fob already knows your car's security code, and a fresh battery will restore it to working order.
If you are buying a brand-new fob (because the old one is damaged or lost), that fob will need to be programmed to your car. Programming usually happens at a dealership or a locksmith who specializes in car keys. The cost ranges from $50 to $200 depending on your vehicle and location.
Some newer cars allow you to program a fob yourself using a sequence of button presses and key turns in the ignition, but this varies widely by manufacturer. Check your owner's manual or call the dealership to see if your car supports self-programming.
Frequently Asked Questions
Can I use a different battery type if I cannot find the exact one?
No. CR2032, CR2025, and CR2016 are different thicknesses and will not fit properly in a holder designed for a different size. Using the wrong battery can damage the fob or cause poor contact. Always use the exact type printed on your old battery.
Do I need to reprogram my fob after changing the battery?
No. Changing the battery does not erase the fob's programming. Once you install a fresh battery, the fob should work when ready without any additional steps.
What should I do with the old dead battery?
Coin-cell batteries contain lithium and should not go in the trash. Most drugstores and supermarkets have a battery recycling bin near the checkout or customer service desk. Some auto parts stores also accept them. Call ahead to confirm your local store takes them.
Is it cheaper to replace the battery myself or have a shop do it?
Replacing it yourself costs $3 to $8 for the battery and takes one minute. A shop will charge $10 to $30 in labor plus the cost of the battery. Unless you are uncomfortable opening the fob, doing it yourself saves money.
Why does my new fob battery die so quickly?
If a fresh battery dies in weeks instead of years, the fob likely has a short circuit or water damage inside. The circuit board is drawing power constantly even when you are not using it. A replacement fob is usually the only fix at that point.