Most car key batteries last three to four years and cost $3 to $10 to replace
A dead key fob battery is one of the easiest car problems to fix yourself. The battery inside your fob typically dies before anything else fails, and you can swap it out in under a minute with no tools or special knowledge. The hardest part is usually finding the seam that opens the fob case.
You do not need to visit a dealership or a mechanic for this job. A new battery costs a few dollars at any pharmacy, grocery store, or hardware store. The only thing you need to know before you start is which battery type your fob uses — and that information is printed on the old battery itself.
Key Takeaways
- Most car key fobs use a coin-cell battery (CR2032, CR2025, or similar) that you can buy at any drugstore for $3 to $10.
- Open the fob by finding the seam between the two halves and gently prying with a flathead screwdriver or coin — do not force it.
- Note which side of the battery faces up before you remove it, then install the new battery the same way.
- If your fob has a metal key blade inside, be careful not to lose the small spring or contact that may fall out when you open it.
Finding the seam and opening your fob
Look at the edge of your key fob for a thin line running around the perimeter. That line is the seam where the two plastic halves meet. Some fobs have a small slot or notch cut into the edge to make it easier to pry open — if yours has one, start there.
Use a flathead screwdriver, a coin, or a plastic pry tool to gently work the seam open. Insert the edge into the slot and twist slightly, then move around the perimeter. Do not hammer or force it — the plastic cracks easily. Once you feel the halves start to separate, you can usually pull them apart by hand.
If your fob has a metal key blade, it will stay attached to one half when you open it. Be aware that a small spring or metal contact may fall out — set these aside on a clean surface so you do not lose them.
Identifying and removing the old battery
Inside the fob you will see a small round battery, usually silver or gold. The battery type is printed on its surface — common types are CR2032, CR2025, CR2016, and CR2430. Write down this number or take a photo before you remove the battery, because you will need it to buy the replacement.
Note which side of the battery faces up — the positive side is usually marked with a + symbol and faces toward you. Gently pry the battery out with your fingernail or a plastic tool. Do not use a metal screwdriver directly on the battery itself, as this can damage the contacts inside the fob.
Installing the new battery
Buy a replacement battery with the same number you noted from the old one. When you open the package, handle the battery by its edges, not its flat surfaces — oils from your skin can interfere with the electrical contact.
Insert the new battery into the fob with the positive side (+) facing the same direction as the old battery faced. It should sit flat and snug in the battery compartment. If it does not fit or feels loose, you may have the wrong battery type — check the number again.
Reassembling the fob and testing
If you removed a spring or metal contact when you opened the fob, reinstall it now in the same position. Align the two halves of the fob and press them together firmly until you hear or feel a click. The seam should be tight and flush all the way around.
Test the fob by pressing each button — lock, unlock, and trunk if your car has one. All buttons should respond when ready. If a button does not work, open the fob again and check that the battery is seated properly and facing the right direction. If the battery is correct and the button still does not work, the fob itself may have a problem and you should contact your car's dealership.
What to do if you cannot open the fob
Some fobs are glued shut or have a design that makes the seam hard to find. If you have tried gently prying around the entire edge and the fob will not budge, stop — forcing it will crack the plastic and make the problem worse.
Your dealership can open and replace the battery for you, usually for $50 to $150 depending on the car brand. A locksmith may also offer this service for less. If your fob is still under warranty, the dealership may do it for free.
When a new battery does not fix the problem
If you installed a fresh battery and the fob still does not work, the problem is not the battery. The fob may have water damage, a broken button, or a failed circuit board. In this case, you will need a replacement fob from your dealership or a locksmith.
Before you buy a new fob, try one more thing: some cars allow you to reprogram an old fob by turning the ignition on and off a certain number of times. Your car's owner manual or the dealership can tell you if your model supports this. If reprogramming does not work, a new fob is your only option.
Frequently Asked Questions
Can I use a different battery type if I cannot find the exact one?
No. Battery types that look similar (like CR2032 and CR2025) have different thicknesses and voltages. Using the wrong type can damage the fob's circuit board or cause buttons to work intermittently. Buy the exact type printed on your old battery.
How long does a new battery last?
Most car key fob batteries last three to four years with normal use. Heavy use — pressing buttons many times per day — can shorten this to two years. You will notice the fob becoming less responsive before the battery dies completely.
What if I lost the old battery and do not know what type to buy?
Check your car's owner manual — it usually lists the battery type. You can also call your dealership with your car's year, make, and model, and they will tell you. Most common fobs use CR2032, so that is a safe guess if you need to buy one today.
Is it safe to replace the battery myself?
Yes. The voltage in a key fob battery is too low to cause injury. The only risk is damaging the plastic fob if you force it open, so work slowly and gently. If you are uncomfortable opening it, a locksmith or dealership can do it for you.