Most key fob batteries cost $3 to $8 and take five minutes to swap

A dead key fob battery is one of the easiest car repairs you can do yourself. You do not need tools beyond what you probably have at home — a coin or small flathead screwdriver — and the battery itself costs less than a coffee. The whole job takes about five minutes once you have the right battery type in hand.

The hardest part is usually figuring out which battery your fob needs. Most common key fobs use a coin-cell battery: CR2032, CR2025, or CR2016 are the most frequent. The number tells you the size and voltage. You can find the correct type by checking your owner's manual, looking it up online by your car's year and model, or opening the fob and reading the number printed on the old battery itself.

Once you know the battery type, buy a replacement at any pharmacy, grocery store, or dollar store — they all stock these batteries in the same aisle as watches and hearing aids. Bring your old fob with you if you are unsure, and a store employee can confirm the match in seconds.

Key Takeaways

  • Most key fob batteries are coin-cell types (CR2032, CR2025, or CR2016) that cost $3 to $8 and last three to four years.
  • You can find the correct battery type in your owner's manual, by searching your car's year and model online, or by reading the number on the old battery itself.
  • The replacement process requires only a coin or small flathead screwdriver and takes about five minutes.
  • If your fob still does not work after the battery swap, the problem is likely a worn button contact or water damage, not the battery.

How to open your key fob safely

Most key fobs split into two halves held together by a seam. Look for a small slot or notch along the edge — this is where you insert your coin or screwdriver. Gently twist or pry to separate the two halves. Do not force it; if it does not budge, you may be pushing in the wrong spot.

Some fobs have a small button or slider on the back that releases the battery cover without opening the whole case. Check the back of your fob first — if you see a button labeled "press" or a sliding tab, try that before attempting to pry the case open.

Once the fob is open, you will see the battery sitting in a small metal holder or slot. Note which side is facing up — the positive side (marked with a + sign) usually faces toward you. Take a photo with your phone if you think you might forget the orientation.

Removing and replacing the battery

Gently pry the old battery out of its holder using your coin or screwdriver. It should come free with light pressure; if it is stuck, try working the tool around the edge rather than pushing straight up. Some batteries sit loosely and will straightforward fall out once the fob is open.

Before you insert the new battery, wipe the metal contacts inside the fob with a dry cloth or cotton swab. Dust and corrosion on these contacts can prevent the new battery from making a good electrical connection, which is a common reason a fob stops working even after a fresh battery.

Slide the new battery into the holder with the positive side facing the same direction as the old one was facing. It should sit flat and snug. Do not force it — if it does not fit easily, you may have the wrong battery type or the wrong orientation.

Closing the fob and testing it

Press the two halves of the fob back together until you hear or feel a click. The seam should be flush all the way around with no gaps. If one side is higher than the other, open it again and make sure the battery is sitting flat in its holder.

Test the fob by pressing each button — lock, unlock, and trunk if your fob has one. You should see the car respond when ready. If nothing happens, open the fob again and check that the battery is oriented correctly and making contact with the metal terminals.

What to do if the new battery does not work

If your fob still does not respond after installing a fresh battery, the problem is usually not the battery itself. The most common culprit is worn rubber contacts on the buttons inside the fob. These contacts wear down over time and eventually stop conducting electricity, even with a good battery in place.

Water damage is the second most common reason. If your fob has been dropped in water or exposed to high humidity, corrosion on the circuit board or battery contacts can prevent it from working. In this case, opening the fob and letting it dry in a warm place for 24 to 48 hours sometimes fixes the problem, but not always.

If neither of these fixes works, you will need a replacement fob. You can buy an aftermarket fob online for $15 to $40 and program it yourself using a procedure found in your owner's manual, or you can have a dealership or locksmith program one for you, which typically costs $100 to $200.

How long a key fob battery lasts

A typical coin-cell battery in a key fob lasts three to four years with normal use. If you use your fob heavily — pressing the buttons many times a day — the battery may wear out in two to three years. Light use can stretch it to five years or longer.

You will notice the fob starting to fail before the battery is completely dead. The buttons may require harder presses, or the fob may work only from a shorter distance. These are signs the battery is running low and a replacement is coming soon.

Mark the date you install a new battery on your calendar or in your phone. This way you will have a rough idea when the next replacement is due and can watch for early warning signs.

Where to buy key fob batteries

Coin-cell batteries are sold almost everywhere: pharmacies like CVS and Walgreens, grocery stores, dollar stores, hardware stores, and online retailers like Amazon. Prices are usually the same everywhere — $3 to $8 per battery — so convenience matters more than cost.

If you are unsure which battery type you need, bring your fob with you to a pharmacy or store. A staff member can open it and match the battery in under a minute. This is faster and more reliable than guessing based on your car's model.

Some dealerships sell key fob batteries, but they typically charge more than retail stores. Unless you are already at the dealership for another reason, a pharmacy or grocery store is your better option.

Frequently Asked Questions

Can I use a different battery type if I cannot find the exact one?

No. Different coin-cell batteries have different voltages and sizes, and using the wrong one can damage your fob or cause it to malfunction. CR2032, CR2025, and CR2016 are not interchangeable. Always match the number printed on your old battery or check your owner's manual.

What if I drop the battery inside the fob and cannot find it?

Open the fob completely and look inside with a flashlight. Coin-cell batteries are small but visible. If it has fallen into a crevice, tilt the fob gently or use a small piece of tape stuck to the end of a pencil to fish it out. Do not shake the fob hard or you may damage internal components.

Is it safe to replace the battery myself, or should I go to a dealership?

It is completely safe to do it yourself. You are not working with electricity or anything that can hurt you. The worst that can happen is the fob does not work afterward, in which case you open it again and check your work. A dealership will charge you $50 to $100 for the same five-minute job.

Why does my new battery work for a few days and then stop?

This usually means the battery is not making good contact with the metal terminals inside the fob. Open it again, remove the battery, and clean both the battery and the metal contacts with a dry cloth. Reinstall the battery and make sure it sits flat and snug in its holder.

Can I replace the battery while the fob is still in my car?

Yes. You do not need to remove the fob from your car or do anything special. Just open it, swap the battery, close it, and test it. Your car will not lock or unlock itself because the fob is not working — the fob only sends a signal when you press a button.