Most car key fob batteries take five minutes to replace and cost between $3 and $10
A dead key fob battery is one of the easiest car problems to fix yourself. The battery sits inside a plastic case that opens with a coin or small flathead screwdriver — no special tools needed. Once you open it, you slide out the old battery, note which side faces up, and slide in a new one of the same type. The whole job takes longer to find your coin than to do the work.
The hardest part is knowing which battery type your fob uses. Car manufacturers use different sizes depending on the model year and brand. A quick search for your car's year, make, and model plus "key fob battery" will tell you whether you need a CR2032, CR2025, or another type. You can also open the fob and read the number printed on the old battery itself.
Key Takeaways
- Key fob batteries are sold at drugstores, supermarkets, and hardware stores for $3 to $10, and most cars use either a CR2032 or CR2025 size.
- You can open the fob with a coin or small flathead screwdriver by finding the seam between the two plastic halves and gently prying them apart.
- The battery slides out and in — pay attention to which side (marked + or −) faces up so you install the new one the same way.
- If the fob still does not work after you replace the battery, the problem is likely a broken button contact or water damage inside the case, not the battery itself.
Finding the seam and opening the fob
Key fobs have two plastic halves held together by a small metal or plastic clip. Look at the edge of your fob and you will see a thin line running around it — that is the seam. Slide a coin (a dime or penny works) or a small flathead screwdriver into the seam and gently twist. Do not force it; a light rocking motion usually pops the halves apart.
Some fobs have a small slot or notch on one edge marked with an arrow or line. If you see one, start there — that is where the manufacturer designed the opening point. Once you feel the clip give way, the two halves will separate. Be gentle so you do not crack the plastic or lose the small spring or contact pad that may fall out when you open it.
Removing and replacing the battery
Inside the fob you will see a round, flat battery sitting in a small metal or plastic holder. The battery has a + symbol on one side and a − symbol on the other. Before you touch it, take a photo or make a mental note of which side faces up. This matters — if you install the new battery upside down, the fob will not work.
Gently pry the old battery out with your fingernail or the edge of your coin. It should come free easily. Take the new battery (the same type number as the old one) and slide it into the holder with the + side facing the same direction as the old battery faced. You should hear or feel a small click as it seats. Close the fob by pressing the two halves together until the clip snaps back into place.
Identifying the correct battery type
The easiest way to know what battery you need is to look at the old one. When you open the fob, the battery will have a code printed on it — usually something like CR2032, CR2025, or CR2016. Write that number down or take a photo, then buy a replacement with the same code.
If you want to know before you open the fob, search online for your car's year, make, model, and "key fob battery type." Most car forums and owner manuals list this information. You can also call your car dealer's parts department and give them your vehicle identification number (VIN) — they will tell you the battery type in seconds.
Where to buy a replacement battery
Key fob batteries are sold almost everywhere: drugstores like CVS and Walgreens, supermarkets, hardware stores, and online retailers. A single battery costs $3 to $10 depending on the brand and where you buy it. Some stores sell them in multipacks for slightly less per battery if you want spares.
You do not need a special brand — a generic CR2032 works just as well as a name-brand one. Check the expiration date on the package (batteries do expire) and make sure the code matches what you need. If you are unsure which aisle they are in, ask a store employee — they are usually near the watch batteries or in the pharmacy section.
Testing the fob after you replace the battery
Once you close the fob, test it right away by pressing each button while standing near your car. You should see the lights flash or hear the locks click. If nothing happens, open the fob again and check that the battery is seated all the way in the holder and that the + side is facing the correct direction.
If the fob still does not work after you flip the battery or try a fresh one, the problem is probably not the battery. Water may have gotten inside the case and corroded the contacts, or one of the rubber buttons may have worn through. In that case, the fob itself needs repair or replacement — a job for your car dealer or a locksmith.
Signs your key fob battery is dying
A dying battery usually shows itself gradually. The buttons may require harder presses than they used to, or you have to stand closer to your car for the fob to work. The range shrinks first — you might notice you can no longer unlock the car from across a parking lot. Eventually the fob stops working entirely.
If the fob suddenly stops working with no warning, the battery may have failed completely, or something else may have broken inside. A battery that dies slowly gives you time to buy a replacement. A battery that dies suddenly could also mean water got inside the case, especially if you dropped the fob or live in a humid climate.
Frequently Asked Questions
Can I use any CR2032 battery or does it have to be a specific brand?
Any CR2032 works — the code is the standard size, not a brand name. Generic batteries from drugstores work just as well as name brands and cost less. The only thing that matters is that the code matches what your fob needs.
What do I do if I lose the small spring or rubber pad when I open the fob?
If a small metal spring falls out, it usually goes back in the same spot — it holds the battery in place. If a rubber pad comes loose, it is the contact that presses against the battery. Both can be put back in by hand before you close the fob. If you cannot find a piece, your fob will not work until you replace it.
How long does a key fob battery usually last?
Most key fob batteries last three to four years with normal use. Heavy use — pressing the buttons many times a day — can shorten that. Cold weather and humidity can also drain batteries faster. There is no way to predict exactly when yours will die, but replacing it every few years prevents being locked out.
Will my car still work if my key fob battery is dead?
Your car will still start and run. You can unlock the door manually with the physical key hidden inside most fobs, or use the keypad on your door if your car has one. You just lose the convenience of remote locking and unlocking until you replace the battery.
What if the fob still does not work after I replace the battery?
Open it again and check that the battery is fully seated in the holder and the + side faces the right direction. If that does not fix it, try a fresh battery from a different package — the first one may have been defective. If a new battery does not work, the fob itself is damaged and needs repair or replacement from a dealer or locksmith.