Most car key fob batteries take five minutes to swap out yourself
You can replace a dead key fob battery without a mechanic or special tools. The battery sits inside a plastic case that opens with a coin or flathead screwdriver — no dealership visit needed. The whole job takes about five minutes, costs between $3 and $15 for the battery, and works the same way across most car brands.
The hardest part is finding the right battery type for your fob. Car key fobs use coin-cell batteries, usually CR2032, CR2025, or CR2016. Your owner's manual lists which one your fob needs, or you can open the fob and read the number printed on the old battery itself.
Key Takeaways
- Most key fob cases open with a coin or flathead screwdriver inserted into a slot on the edge, and the battery slides or pops out once the case is apart.
- Write down or photograph the battery type number before you buy a replacement, because CR2032, CR2025, and CR2016 look identical but are not interchangeable.
- When you reassemble the fob, make sure the battery sits flat in its holder with the positive side facing up — the side marked with a plus sign or the shiny side.
- If the fob still does not work after you install a fresh battery, the problem is likely a broken button contact or water damage inside the case, not the battery itself.
How to open the key fob case
Look for a seam or slot running around the edge of your fob. Most fobs have a thin line where the two plastic halves meet. Insert a coin — a dime or penny works — or a flathead screwdriver into that slot and twist gently. The case will pop apart into two pieces.
Some fobs have a small button or latch on the back instead of a seam. Press or slide that button and the case will separate. If you cannot find either, check your owner's manual for your specific car model, because a few luxury brands use proprietary cases that require a different approach.
Once the case is open, you will see the battery sitting in a plastic holder. It is a small, flat, silver coin about the size of a dime. Do not force anything — if the case will not budge after gentle twisting, you may have the wrong angle or the wrong tool.
Removing and replacing the battery
The battery either slides out or pops out depending on the holder design. If it slides, push it gently to one side and it will come free. If it pops, there is usually a small lip or spring underneath — press down on the battery and it will flip up and out of the holder.
Before you throw the old battery away, look at the top or bottom for a number like CR2032 or CR2025. Write that number down or take a photo. This is the battery type you need to buy. Do not guess — the three common types look nearly identical but will not work in the wrong fob.
When you install the new battery, pay attention to which side faces up. Most coin-cell batteries have a plus sign (+) printed on one side — that is the positive side and it should face up, toward the buttons of the fob. If you install it upside down, the fob will not work.
Closing the fob and testing it
Once the battery is seated flat in its holder, line up the two halves of the case and press them together firmly. You should hear or feel a click when they snap back into place. If they do not close all the way, the battery may be sitting crooked — open the case again and reseat it.
Test the fob by pressing each button — lock, unlock, trunk, panic — and watching your car respond. If the fob works, you are done. If it does not, open the case again and check that the battery is facing the right direction and sitting all the way down in the holder.
Where to buy the right battery
Coin-cell batteries are sold at pharmacies, grocery stores, hardware stores, and online retailers. Walgreens, CVS, Walmart, and Target all stock them in the watch and battery section. You can also order them online from Amazon or eBay. A single battery costs between $3 and $8 at a store, or you can buy a pack of four or five for $10 to $15.
Some car dealerships sell key fob batteries, but they charge more — often $10 to $20 for a single battery plus labor if you want them to install it. Since the job takes five minutes and requires no special knowledge, buying the battery yourself and doing the swap at home saves money.
What to do if the fob still does not work
A new battery fixes most dead fobs, but not all. If your fob does not work after you install a fresh battery and close the case properly, the problem is usually inside the fob itself. The rubber button contacts wear out over time, or water has gotten inside the case and corroded the circuit board.
You can try opening the fob again and gently cleaning the rubber button pad and the metal contacts on the circuit board with a dry cotton swab. If that does not help, the fob likely needs to be replaced. Some car dealerships will program a new fob to your car for $100 to $300, depending on the brand. Aftermarket fobs from online retailers cost $20 to $60 and often come with programming instructions.
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 voltages. Using the wrong type may not fit in the holder, or it may fit but not power the fob correctly. Always match the number printed on your old battery or listed in your owner's manual.
What if I lose a screw or the case will not close?
Most key fobs do not have screws — they snap together. If yours does have a screw and you lose it, a hardware store can sell you a replacement in the same size. If the case will not close after you snap it back together, the battery is probably sitting crooked. Open it again and reseat the battery so it lies flat.
How long does a key fob battery last?
Most coin-cell batteries last three to four years in a key fob, depending on how often you use it. Heavy use drains the battery faster. When the fob starts to work only when you hold it close to the car, the battery is dying and needs replacement.
Is it safe to replace the battery myself?
Yes. The battery is not dangerous to handle, and you cannot damage the car by opening the fob. The only risk is installing the battery upside down, which straightforward means the fob will not work until you flip it over. Wash your hands after handling the battery if you have sensitive skin.
What if the fob gets wet?
If your fob gets wet, open the case and let both the battery and the inside of the fob dry completely for 24 hours. You can place them in a warm, dry spot or use uncooked rice to absorb moisture. Once dry, reinstall the battery and test the fob. If it still does not work, water may have damaged the circuit board and the fob will need replacement.