Most key fob batteries cost $3 to $10 and take less than five minutes to swap out yourself
You can replace a key fob battery without a mechanic or dealership visit. The battery itself is inexpensive — usually between $3 and $10 — and the process requires only a small flathead screwdriver or coin. Most fobs open by prying the seam between the two halves, though some models use a small screw on the back or side. Once open, you'll note which way the old battery sits (the + side faces up or down depending on the fob), remove it, and drop in the new one the same way.
The hardest part is knowing which battery size your fob needs. Common sizes are CR2032, CR2025, and CR2016 — the numbers refer to the battery's diameter and thickness in millimeters. Your owner's manual lists the correct size, or you can take the old battery to any pharmacy, grocery store, or hardware store and they'll match it for you. Once you have the right battery, the swap takes about two minutes.
Key Takeaways
- Most key fob batteries cost $3 to $10 and are sold at pharmacies, grocery stores, and hardware stores without needing to visit a dealership.
- The correct battery size is printed in your owner's manual or stamped on the old battery itself — common sizes are CR2032, CR2025, and CR2016.
- Open the fob by prying the seam with a flathead screwdriver or coin, or by removing a small screw on the back, depending on your model.
- Note which direction the old battery faces before removing it, then insert the new battery the same way to avoid reversing the polarity.
- If the fob still doesn't work after the battery swap, the problem is likely a worn contact or a broken circuit board, not the battery.
Finding the right battery size for your fob
The battery size is almost always printed on the old battery itself. Remove the fob's case first, take out the dead battery, and look at the top or bottom surface — you'll see a code like CR2032 or CR2025. Write this down or take a photo, then buy a replacement with the exact same code.
If the old battery is too corroded to read, check your owner's manual. Search for "key fob battery" or "remote battery" in the index. The manual will list the size and sometimes the brand (Energizer, Duracell, and Panasonic make most fob batteries). If you don't have the manual, search online for "[your car year, make, model] key fob battery size" and you'll find the answer in seconds.
You can also take the fob to any pharmacy, grocery store, or hardware store with a battery section. Show the employee the open fob or the old battery, and they'll match it for you. This takes one minute and costs nothing.
Opening the fob without breaking it
Most fobs split into two halves along a seam that runs around the edge. Look for a thin line where the plastic meets — this is where the two pieces separate. Slide a flathead screwdriver or coin (a dime or penny works) into the seam and gently twist to pry the halves apart. Work your way around the edge rather than forcing one spot, which can crack the plastic.
Some fobs have a small screw on the back or side instead of a seam. If you see a screw, use a screwdriver that fits snugly — a too-small screwdriver will strip the screw head and make it impossible to open. Once the screw is out, the two halves will pull apart by hand.
A few luxury car fobs use a sliding button or a release tab on the side. Check the back of the fob for any label or arrow that says "press here" or "slide." If you're unsure, search online for "[your car model] key fob how to open" and you'll find a photo or video showing the exact method.
Removing and replacing the battery
Once the fob is open, look at how the battery sits inside. The + (positive) side faces either up or down — this matters. Take a photo or make a mental note before you touch anything. Some fobs have a small metal clip or spring that holds the battery in place; if yours does, gently lift or slide this clip to release the battery.
Lift out the old battery and set it aside. Drop the new battery into the same spot, making sure the + side faces the same direction as the old one did. If the battery doesn't sit flat or feels loose, you may have reversed it — flip it over and try again. The battery should sit snugly without any rocking.
Close the fob by pressing the two halves together until you hear a click or feel them snap into place. If your fob had a screw, replace it now. Test the fob by pressing each button — the lights on your car should flash or the door should lock and unlock. If nothing happens, open the fob again and check that the battery is facing the right direction.
What to do if the new battery doesn't fix the problem
If the fob still doesn't work after the battery swap, the issue is not the battery. The most common culprit is a worn or corroded contact — the small metal piece inside the fob that touches the battery. If you see green or white corrosion on the metal contacts, gently clean them with a pencil eraser or a dry cloth. This often restores the connection.
If the contacts look clean and the fob still doesn't work, the circuit board inside may be damaged. This is not something you can fix at home. You'll need to buy a replacement fob from a dealership or a third-party seller. Dealership fobs are more expensive but are programmed to your car; third-party fobs are cheaper but may require programming at a dealership or by a locksmith.
Before you buy a new fob, test whether your car's locks still work with the physical key. If they do, your car is fine — only the fob is broken. This tells you that a replacement fob is your only option, not a repair to the car itself.
Where to buy replacement batteries and fobs
Replacement batteries are sold at pharmacies (CVS, Walgreens), grocery stores (most have a battery section near the checkout), hardware stores (Home Depot, Lowe's), and online retailers (Amazon). Prices are the same everywhere — usually $3 to $10 for a single battery. Buy one or two extras so you have a spare on hand.
If you need a replacement fob, dealerships sell them for $150 to $400 depending on your car. Third-party fobs sold on Amazon or eBay cost $20 to $80 but may need programming. Some locksmiths program fobs for $50 to $150. Call your dealership first to ask whether a third-party fob will work with your car and whether they'll program it for a fee.
Frequently Asked Questions
How long does a key fob battery last?
Most key fob batteries last three to four years with normal use. If you use your fob many times a day, the battery may wear out in two to three years. If you rarely use it, it may last five years or longer. There's no way to predict exactly when it will die, so keep spare batteries on hand.
Can I use a different battery size if I can't find the exact one?
No. Using the wrong size battery can damage the fob or cause it to malfunction. The battery must fit snugly in the compartment, and the voltage must match what the circuit board expects. Always use the exact size listed on the old battery or in your manual.
What if I put the battery in backwards?
If you reverse the polarity, the fob won't work and you may damage the circuit board. Open the fob immediately and flip the battery to face the correct direction. If you left it reversed for more than a few seconds, the fob may be permanently damaged and you'll need a replacement.
Do I need to reprogram my fob after changing the battery?
No. Changing the battery does not erase the fob's programming. Once you insert the new battery and close the fob, it should work right away. If it doesn't, the problem is not the battery or programming — it's a worn contact or a broken circuit board.
Can I change the battery myself or do I need a mechanic?
You can change it yourself in about five minutes with a screwdriver or coin and a new battery. There is no risk of damaging your car, and the battery is inexpensive. A mechanic or dealership will charge you $50 to $100 for the same job, so doing it yourself saves money and time.