Replacing a key fob battery is usually a five-minute job you can do at home with no tools
Most key fobs use a coin-cell battery — typically a CR2032, CR2025, or CR2016 — that you can buy at any drugstore, grocery store, or hardware store for two to five dollars. The fob itself snaps open along a seam, you slide out the old battery, slide in the new one with the correct side facing up, and snap it closed. You do not need to reprogram the fob or visit a dealer. The whole process takes longer to describe than to do.
The hardest part is usually finding the seam where the fob opens. Most fobs have a small slot or notch on one edge; a flathead screwdriver, coin, or even a fingernail can pry it open. Some fobs have a button you press to release the battery cover. Once you see how yours opens the first time, you will know for next time.
Key Takeaways
- Key fob batteries cost two to five dollars and are sold at drugstores, grocery stores, and hardware stores under names like CR2032 or CR2025.
- The fob snaps open along a seam; look for a small slot or notch on the edge where you can insert a flathead screwdriver or coin to pry it apart.
- When you install the new battery, the flat side (marked with a + or -) must face the correct direction — check the old battery or look inside the fob for a label.
- After you close the fob, test it when ready by pressing a button; if it does not work, the battery may be installed backwards or the fob may need a different battery type.
Finding out what battery your fob needs
The easiest way is to look at the old battery after you open the fob. The battery type is printed on one side — CR2032, CR2025, CR2016, or similar. Write down the number or take a photo, then buy that exact type.
If you want to know before you open the fob, check your car's owner manual or search online for your car's year, make, and model plus "key fob battery." Most common cars use CR2032, but some use CR2025 or CR2016. Buying the wrong size will not damage anything; it straightforward will not fit or will not work. If you buy the wrong one, you can return it and swap it for the right type.
How to open the fob without damaging it
Look around the edge of the fob for a thin seam or slot. Most fobs have one on the side or bottom. Insert a flathead screwdriver, coin, or butter knife into the slot and gently twist or pry. The two halves should separate. If you cannot find a seam, check for a small button or lever on the back — some fobs release the battery cover by pressing or sliding this.
Do not force it. If you are prying and nothing is moving, you are probably looking at the wrong edge. Rotate the fob and try the next edge. Once you find the right spot, it usually pops open with very little pressure. If the fob is old or the plastic is brittle, go slowly to avoid cracking it.
Installing the new battery correctly
When you open the fob, you will see the old battery sitting in a small metal holder or slot. Note which side is facing up — one side is flat and marked with a + or -, and the other side is domed. The marking shows you which direction the battery must face.
Remove the old battery by gently prying it up or sliding it out. Place the new battery in the same position, with the marked side (+ or -) facing the same direction as the old one faced. If you are unsure, look inside the fob for a small + or - printed on the plastic — that tells you which side of the battery should face that direction. Close the fob by snapping the two halves together until you hear or feel a click.
Testing the fob and troubleshooting if it does not work
Press any button on the fob — lock, unlock, or trunk — and watch your car. The lights should flash or you should hear the locks click. If nothing happens, open the fob again and check that the battery is facing the right direction. Flip it over and try again.
If the fob still does not work after you flip the battery, the battery may be dead (rare for a new one) or you may have the wrong battery type. Try a different battery type — if your fob uses CR2032 but you installed CR2025, it might not work. Return the battery and buy the correct size. If you have tried the right battery in both directions and the fob still does not work, the fob itself may be damaged and may need to be replaced by a dealer.
When to replace the whole fob instead of just the battery
If the fob is cracked, the buttons are stuck or broken, or water has gotten inside, replacing the battery will not fix it. A new fob from a dealer or third-party seller usually costs thirty to one hundred fifty dollars, depending on your car. Some dealers will program a used fob you buy online for a smaller fee than selling you a new one.
If you are not sure whether the fob itself is broken or just the battery, replace the battery first. It costs almost nothing and solves the problem in most cases. If the fob still does not work after you install a fresh battery in the correct direction, then you know the fob needs to be replaced.
Frequently Asked Questions
Can I use a different battery type if I cannot find the exact one?
Not reliably. CR2032, CR2025, and CR2016 are different sizes. Using the wrong size may not fit in the holder, or it may work briefly but drain faster. Buy the correct type — it costs the same and is sold everywhere.
Do I need to reprogram the fob after I replace the battery?
No. The fob stores its code in a chip that runs on the battery power. Replacing the battery does not erase the code. Once you close the fob with the new battery, it should work when ready.
What if I installed the battery backwards and now the fob does not work?
Open the fob and flip the battery over so the other side faces the opposite direction. Close it and test again. A backwards battery will not damage the fob; it straightforward will not send a signal.
How long does a key fob battery usually last?
Most key fob batteries last three to four years with normal use. If you use the fob very frequently, it may last one to two years. There is no way to predict exactly when it will die, so replace it as soon as the fob stops working.
Is it safe to replace the battery myself, or should I go to a dealer?
It is completely safe to replace it yourself. There is no risk of electric shock, and you cannot damage the fob by opening it. Dealers charge fifteen to fifty dollars for the same five-minute job, so doing it at home saves money and time.