Most car fob batteries are coin-cell batteries you can swap yourself without tools
Your car fob battery usually dies before anything else on the fob does. The battery is almost always a coin-cell type — the same flat, round battery in a watch or calculator — and you can replace it in under five minutes with nothing but your fingernail or a flathead screwdriver. The fob case splits open, you slide out the old battery, slide in a new one the same size, and snap it shut. No dealer visit, no special equipment.
The hardest part is finding out which battery size your fob uses. That information is printed inside the fob case once you open it, or you can check your owner's manual. Most common sizes are CR2032, CR2025, and CR2016 — all available at any drugstore, grocery store, or hardware store for two to five dollars.
Key Takeaways
- Car fob batteries are coin-cell types that you can replace without tools by prying the case open with your fingernail or a flathead screwdriver.
- The battery size is printed on the inside of the fob case or in your owner's manual — write it down before you go to the store.
- Coin-cell batteries cost two to five dollars and are sold at drugstores, grocery stores, and hardware stores.
- When you slide the new battery in, the flat side faces up and the ridged side faces down, matching the way the old one sat.
- If the fob still does not work after you replace the battery, the problem is usually a corroded contact or a broken button, not the battery itself.
Find your fob battery size before you buy
Open your owner's manual and search for "key fob battery" or "remote battery." Most manuals list the size in the maintenance or specifications section. Write down the number — it will look like CR2032 or CR2025.
If you do not have the manual, open the fob case first (see the next section), and you will see the battery size printed on the metal case inside. Take a photo with your phone so you have it when you shop. Do not guess — buying the wrong size means a wasted trip back to the store.
Pry open the fob case along the seam
Look at the edge of your fob. You will see a thin seam running around it — this is where the two halves of the plastic case meet. Slide your fingernail or a flathead screwdriver into that seam and gently twist or pry. The case will pop apart. Some fobs split top-to-bottom, others split side-to-side. Work your way around the seam if it does not pop on the first try.
Be gentle. The plastic is thin and can crack if you force it. If your fingernail is not strong enough, a flathead screwdriver works better than a knife — a knife can slip and cut your hand. Once the case is open, set one half aside and look at the battery inside.
Slide out the old battery and note which side faces up
The battery sits in a small metal holder inside the case. One side of the battery is flat and shiny; the other side has a ridge or bump in the center. Look at which side is facing up before you remove it — you need to put the new battery in the same way.
Slide the old battery out with your fingernail or the tip of a screwdriver. If it is stuck, do not force it. A tiny bit of corrosion can make it tight. Gently rock it side to side as you slide it out. Once it is out, look at the metal contacts inside the holder. If they are green or white, wipe them with a dry cloth or a pencil eraser before you put the new battery in.
Insert the new battery with the flat side up
Slide the new battery into the holder with the flat side facing up, matching the way the old one sat. It should slide in smoothly and sit flat. If it does not, you may have the wrong size — check the number on the old battery again.
Once the battery is in place, press down gently to make sure it is seated. You should hear or feel a small click as it settles into the metal contacts. Do not force it. If it does not sit flat, remove it and check that you have the right size and that the contacts are clean.
Snap the case shut and test the fob
Line up the two halves of the case and press them together firmly. You should hear a click as they snap shut. The seam should be tight all the way around with no gaps. If there is a gap, the case may not be fully seated — press harder or check that you did not accidentally bend the plastic when you opened it.
Now test the fob by pressing each button while standing near your car. The lights should flash and the locks should respond. If nothing happens, remove the case again and check that the battery is seated properly and that the flat side is facing up. If the fob still does not work, the problem is usually corroded contacts or a broken button, not the battery.
What to do if the fob still does not work
If you replaced the battery and the fob is still dead, the contacts inside may be corroded. Remove the battery again and look at the metal contacts — if they are green, white, or discolored, clean them with a pencil eraser or a dry cloth. Reinsert the battery and test again.
If the fob still does not work, one of the rubber buttons under the plastic case may be torn or stuck. This is harder to fix at home and usually means a trip to a dealer or a locksmith. Some dealers will reprogram an old fob for thirty to fifty dollars, or you can buy a new aftermarket fob online for twenty to forty dollars and reprogram it yourself using your owner's manual.
Frequently Asked Questions
Can I use any coin-cell battery or does it have to be the exact size?
It has to be the exact size. CR2032, CR2025, and CR2016 are all different thicknesses and will not fit the holder properly if you use the wrong one. A battery that is too thick will not close the case; one that is too thin will not make contact with the metal holders. Check the number on your old battery or in your manual before you buy.
Which side of the coin battery goes up?
The flat side goes up. The side with the ridge or bump in the center goes down into the metal contacts. Look at how your old battery was sitting before you remove it, and put the new one in the same way. If you put it in backwards, the fob will not work.
How long does a car fob battery usually last?
Most coin-cell batteries last three to four years in a car fob, depending on how often you use it. If you press the buttons dozens of times a day, the battery may only last two years. If you use it sparingly, it might last five years. There is no way to predict exactly when it will die.
Do I need to reprogram my fob after I change the battery?
No. Changing the battery does not erase any programming. The fob will work exactly as it did before once the new battery is in and making contact with the metal holders. If you had to reprogram it, that would mean the battery stores the programming, which it does not.
What if I drop the battery or lose it before I can put it in?
Coin-cell batteries are small and straightforward to lose. If you drop it, look on the floor when ready — they roll. If you lose it, you will need to buy another one, which costs two to five dollars. Buy a spare at the same time so you have a backup the next time the battery dies.