You can replace most key fob batteries yourself with a coin and a new battery from any drugstore

A dead key fob battery is one of the easiest car problems to fix at home. The battery inside your fob is a small, coin-shaped cell — usually a CR2032, CR2025, or CR2016 — that costs between $3 and $8. You do not need tools beyond a coin or flathead screwdriver, and the whole job takes about five minutes. The hardest part is usually just prying the fob open without scratching it.

The process is nearly identical across all car brands. You will open the fob, note which battery type is inside, buy a replacement, swap it out, and snap the case back together. If your fob uses a different design — some luxury cars use fobs that require a screwdriver to open — the steps change slightly, but the principle stays the same.

Key Takeaways

  • Most key fob batteries are standard coin cells (CR2032, CR2025, or CR2016) sold at pharmacies, grocery stores, and online retailers for $3 to $8.
  • You can open a standard fob by inserting a coin or flathead screwdriver into the seam and gently twisting to separate the two halves.
  • Note the battery's orientation — the flat side usually faces up — before removing it, so you can install the new one the same way.
  • If your fob still does not work after replacing the battery, the problem may be a corroded contact or a broken circuit board, not the battery itself.

Identify your fob type and battery size

Before you buy anything, you need to know what battery your fob uses. The easiest way is to open the fob and look at the battery itself. If you have the owner's manual, it may list the battery type on a specifications page or in the maintenance section — search for "battery" or "key fob" in the index.

If you cannot find the manual, call your car dealership's parts department with your vehicle's year, make, and model. They can tell you the battery type in one call. You can also search online for "[your car year/make/model] key fob battery type" and usually find the answer within seconds. Common types are CR2032 (the most common), CR2025, and CR2016. The numbers refer to the battery's diameter and thickness in millimeters.

Open the fob without damaging the case

Most key fobs have a seam running around the edge where the two plastic halves meet. Insert a coin — a dime or penny works well — into this seam, or use a flathead screwdriver if you have one. The goal is not to pry hard, but to explore gentle, steady pressure while you twist the coin slightly, as if you were opening a jar lid.

Start at one corner and work your way around the seam. You will feel the two halves begin to separate. Once there is enough space, you can usually pull the halves apart by hand. If the fob is stuck, do not force it — stop, move to a different spot on the seam, and try again. Forcing it can crack the plastic or damage the circuit board inside.

Some fobs, particularly those from luxury brands, have a small screw holding the case together instead of a snap-fit seam. If you see a screw, use a small Phillips or flathead screwdriver to remove it, then gently pull the halves apart.

Remove the old battery and note its position

Once the fob is open, you will see the battery sitting in a small metal holder or slot. Before you touch it, look at which side is facing up — the flat side or the side with the raised bump. This matters because batteries only work in one direction. Take a mental note or even take a quick photo with your phone so you remember the orientation.

Gently pry the battery out of its holder using your fingernail, a coin edge, or a plastic spoon. Do not use anything sharp that could damage the metal contacts inside the fob. Once the battery is out, check the metal contacts where the battery sits. If they look dark, corroded, or crusty, wipe them gently with a dry cloth or a pencil eraser. Corrosion can prevent a new battery from working even if the battery itself is good.

Install the new battery and close the fob

Take your new battery and insert it into the holder in the same orientation as the old one. If the flat side was facing up before, the flat side should face up now. Push gently until the battery clicks or sits snugly in place. Do not force it — it should sit flat without wobbling.

Now close the fob by aligning the two halves and pressing them together firmly until you hear or feel a click. Start at one end and work your way around, making sure the seam closes evenly. If you removed a screw, replace it now and tighten it gently — do not over-tighten, or you may crack the plastic.

Test the fob and troubleshoot if needed

Stand near your car and press each button on the fob — lock, unlock, trunk, panic, or whatever buttons yours has. You should see the car's lights flash or hear the locks engage. If nothing happens, try pressing the buttons several more times. Sometimes a new battery needs a moment to make full contact.

If the fob still does not work, open it again and check that the battery is seated correctly and facing the right direction. Also look at the metal contacts again — if they are heavily corroded, you may need to clean them more thoroughly with a pencil eraser or a small amount of rubbing alcohol on a cloth. If the contacts look clean and the battery is in the right direction, the problem may be a broken circuit board or a faulty button, which usually requires a replacement fob rather than a battery swap.

Where to buy key fob batteries

You can find key fob batteries at almost any pharmacy or grocery store in the health and beauty section or near the checkout counter. CVS, Walgreens, Target, and Walmart all stock common sizes. Online retailers like Amazon also sell them, often in multi-packs if you want to keep spares on hand. Prices are usually the same everywhere — $3 to $8 per battery depending on the brand and whether you buy a single or a pack.

Some car dealerships sell batteries too, but they typically charge more than retail stores. If you are already at the dealership for another reason, it may be convenient, but there is no reason to make a special trip.

Frequently Asked Questions

How long does a key fob battery last?

Most key fob batteries last three to four years with normal use. If you use your fob frequently — pressing the buttons multiple times a day — the battery may wear out sooner. Cold weather can also drain batteries faster temporarily, though they usually work again once they warm up.

Can I use any CR2032 battery, or does it have to be a specific brand?

Any CR2032 battery will work in your fob, regardless of brand. Duracell, Energizer, Panasonic, and store brands all perform the same. The only difference is sometimes price and how long they last, but for a key fob, a cheaper battery is usually fine.

What if my fob has two batteries inside?

Some fobs, particularly older or larger ones, use two batteries stacked together. If yours has two, replace both at the same time and make sure they are both facing the correct direction. If only one is dead, replacing just that one may work, but replacing both ensures the fob will work reliably.

Is it dangerous to replace the battery myself?

No. Key fob batteries are low-voltage and pose no shock risk. The only real danger is dropping a small battery where a child or pet could swallow it, so keep the old and new batteries out of reach. Wash your hands after handling batteries, as they can contain trace metals.

Why does my fob still not work after I replaced the battery?

If a new battery does not fix the problem, the issue is usually corroded contacts inside the fob, a broken button, or a damaged circuit board. Try cleaning the metal contacts with a pencil eraser or rubbing alcohol. If that does not work, you likely need a replacement fob from your dealership or an aftermarket supplier.