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. You do not need tools or special knowledge — most key fobs open with a coin or your fingernail, the battery slides out, and a new one slides in. The whole job takes five minutes. If your key fob stops working, the battery is the first thing to check before you assume the fob itself is broken.
The battery type depends on your car's make and model. Most common fobs use a CR2032, CR2025, or CR2016 coin cell battery, which you can buy at any pharmacy, grocery store, or hardware store for a few dollars. A few luxury cars use different sizes, but your owner's manual or a quick online search of your car model will tell you which one you need.
Key Takeaways
- Most key fob batteries are coin cells (CR2032 is most common) that cost $3 to $10 and last three to four years.
- Open the fob by sliding a coin into the seam or prying gently with your fingernail — do not force it or you may crack the plastic.
- Note which side of the battery faces up before you remove it, then insert the new battery the same way.
- Test the fob before you leave the store or pharmacy so you can exchange the battery if it does not work.
- If a new battery does not fix the problem, the fob circuit board may be damaged and replacement is usually cheaper than repair.
Identify your key fob battery type before you buy
Open your owner's manual and search for "key fob battery" or "remote battery." The manual will list the exact battery type — usually CR2032, CR2025, or CR2016. If you do not have the manual, search online for "[your car year, make, model] key fob battery" and you will find the answer in seconds.
You can also open the fob first and look at the battery itself. The battery type is printed on the flat side. Write it down or take a photo before you go to the store. This takes 30 seconds and saves you from buying the wrong size.
Open the key fob without breaking it
Look for a seam running around the edge of the fob — this is where the two plastic halves meet. Slide a coin (a dime or penny works) into the seam and twist gently. You should feel the two halves start to separate. Once there is a small gap, switch to your fingernail and pry the halves apart slowly. Do not force it or you will crack the plastic.
Some fobs have a small button or slot on the edge instead of a seam. Press or slide this button and the battery cover will pop out. Check your owner's manual if you cannot find the seam — a few car brands use different designs.
Once the fob is open, you will see the battery sitting in a small plastic holder. It is a flat, round disc, usually silver or gold colored. The holder often has a plus sign (+) or minus sign (−) printed next to where the battery sits. This tells you which side should face up.
Remove the old battery and note its position
Before you touch the old battery, look at which side is facing up. If the plus sign is visible on top, the positive side is up. If you see the minus sign, the negative side is up. Take a photo or write this down — you must insert the new battery the same way.
Gently pry the old battery out with your fingernail or the edge of a coin. It should come out easily. If it is stuck, do not force it — wiggle it gently side to side until it lifts free. Do not touch the flat sides of the new battery with your bare fingers, as oils from your skin can reduce its lifespan. Handle it by the edges only.
Insert the new battery and close the fob
Slide the new battery into the holder with the same side facing up as the old one. If the old battery had the plus sign facing up, the new one should too. Push gently until the battery sits flat in the holder and does not move. You should hear or feel a small click.
Align the two halves of the fob and press them together firmly until they snap. You may hear a click or feel resistance — this is normal. Do not force it so hard that you crack the plastic, but do press until the seam is tight and the fob feels solid in your hand.
Test the fob before you leave the store
Stand near your car and press each button on the fob — lock, unlock, trunk, panic, or whatever buttons your fob has. You should see your car's lights flash or hear the locks click. If nothing happens, go back inside the store when ready. The battery may be defective, or you may have inserted it upside down.
If the fob still does not work after you flip the battery and try again, the problem is likely inside the fob itself — a broken circuit board or corroded contacts. In this case, buying a replacement fob is usually cheaper than trying to repair it. Most car dealerships and online retailers sell replacement fobs for $50 to $150, and many can program them for you on the spot.
Common mistakes that prevent the battery from working
The most common error is inserting the battery upside down. The plus and minus sides look almost identical, so double-check the orientation before you close the fob. If you are not sure, open it again and flip the battery — it takes 10 seconds.
The second mistake is touching the flat sides of the battery with your fingers. Skin oils can create a thin film that blocks electrical contact. If the fob does not work after you insert a new battery, remove it, wipe both sides with a clean, dry cloth, and try again.
A third mistake is not closing the fob tightly enough. If the two halves are not snapped together firmly, the battery may not make full contact with the metal springs inside. Press until you feel resistance and hear a click.
Frequently Asked Questions
What if I cannot open the key fob?
Try a different coin — a dime or quarter may fit the seam better than a penny. If the fob still will not open, check your owner's manual for the specific design. Some fobs have a hidden button or slot rather than a visible seam. If you are still stuck, a car dealership can open it for you, usually for free or a small fee.
Can I use a different battery size if I cannot find the right one?
No. CR2032, CR2025, and CR2016 are different thicknesses and will not fit properly or make contact. Using the wrong size can damage the fob. Buy the correct size — it takes two minutes to look up and costs the same as the wrong battery.
How long does a new key fob battery last?
Most coin cell batteries last three to four years in a key fob, depending on how often you use it. If you press the buttons many times per day, the battery may last only two years. If you use it rarely, it may last five years or longer.
What should I do with the old battery?
Most pharmacies and grocery stores have a battery recycling bin near the checkout. Drop the old battery there. Do not throw it in the trash — batteries contain materials that should be recycled. Some stores will take old batteries even if you did not buy them there.
Why does my new battery not work even though I installed it correctly?
The battery may be defective — try a different new battery from a different package. If a second battery does not work, the fob circuit board is likely damaged. This usually happens after the fob is dropped, exposed to water, or sat in a hot car for a long time. Replacement fobs are the most practical solution.