Most key fob batteries take five minutes to swap out yourself

A dead key fob battery is one of the easiest car problems to fix at home. You do not need tools or special knowledge — just the right battery type and a way to open the fob case. Most fobs use a coin cell battery (the flat, round kind), and once you know which one yours takes, you can buy a replacement at any drugstore or supermarket for two to five dollars. The whole job takes about five minutes.

The hardest part is usually opening the fob without breaking the plastic. Most fobs have a seam you can pry open with a coin or a plastic spoon, but some slide apart or have a hidden screw. Once it is open, the battery sits in a small metal holder — you lift it out, note which side was facing up, and drop in the new one the same way.

Key Takeaways

  • Most car key fobs use a CR2032, CR2025, or CR2016 coin cell battery, which you can find at any pharmacy or grocery store for a few dollars.
  • Check your owner's manual or the inside of your fob case to find out which battery type you need before you buy a replacement.
  • Open the fob by prying gently along the seam with a coin, flathead screwdriver, or plastic spoon — do not force it or you may crack the case.
  • When you drop in the new battery, make sure the positive side (marked with a +) faces up, the same direction the old one was facing.
  • If the fob still does not work after you replace the battery, the problem is likely a broken button contact or water damage inside the case.

Find out what battery type your fob needs

The battery type is printed on the inside of your fob case or in your vehicle's owner's manual. The most common types are CR2032 (the standard size), CR2025, and CR2016. CR2032 is thicker than the others, so putting a CR2025 in a fob designed for CR2032 will not work properly — the battery will rattle and may not make contact.

If you cannot find the manual and the case is already open, look at the old battery itself. The type is stamped right on it. If the fob is still closed and you want to know before you open it, you can also call your car's dealership with your vehicle identification number (VIN) and they will tell you. Most dealerships have this information in their system and can answer in one call.

Open the fob case without breaking it

Look for a seam running around the edge of the fob — this is where the two halves of the plastic case meet. Slide a coin (a dime or penny works well) or a flathead screwdriver into the seam and gently twist to pry the halves apart. Start at one corner and work your way around. Do not force it — if you feel strong resistance, stop and try a different spot along the seam.

Some fobs do not have a visible seam. Instead, they slide apart like a book: hold one half still and slide the other half toward you. A few older or premium fobs have a small screw on the back or inside the battery compartment. If you see a screw, use a screwdriver that fits snugly in the slot — a screwdriver that is too small will strip the screw and make it impossible to open.

Once the case is open, you will see a small metal holder or clip holding the battery in place. The battery itself is a thin, flat disc about the size of a dime.

Remove the old battery and install the new one

Lift the edge of the battery with your fingernail or a plastic spoon to pop it out of the metal holder. Look at which side was facing up — the positive side is marked with a + symbol. The negative side is blank or marked with a −.

Drop the new battery into the holder with the positive side facing the same direction as the old one. It should sit flat and click into place. Do not force it — if it does not sit flush, you may have the wrong battery type or the battery may be upside down.

Close the fob case by pressing the two halves together until you hear or feel a click. If there was a screw, replace it now. Test the fob by pressing each button — you should see the LED light up or hear the lock and unlock sounds from your car.

What to do if the fob still does not work

If the new battery does not bring the fob back to life, the problem is usually inside the case, not the battery itself. Water damage is common — if the fob has been dropped in a puddle or left in a humid environment, moisture can corrode the circuit board or the metal contacts under the buttons. You may see white or green corrosion inside the case.

If the contacts look corroded, you can try cleaning them with a cotton swab dipped in rubbing alcohol. Let the inside dry completely before closing the case. If the fob still does not work, or if you do not see corrosion, the circuit board itself may be damaged. At that point, you will need a replacement fob from your car's dealership or an aftermarket supplier — this usually costs between 50 and 200 dollars depending on your vehicle.

If only one or two buttons stopped working while others still work, the problem is usually a worn rubber button pad inside the case. These can sometimes be replaced, but it is usually cheaper to replace the whole fob.

Where to buy replacement batteries

Coin cell batteries are sold at pharmacies, grocery stores, hardware stores, and online retailers. CVS, Walgreens, Target, and Walmart all stock CR2032, CR2025, and CR2016 batteries in their pharmacy or electronics sections. You can also order them online from Amazon or eBay — a pack of two or four costs three to eight dollars.

Buy a name brand if you can — Energizer, Duracell, and Panasonic are reliable. Generic batteries work too, but they sometimes have shorter shelf lives. Since you only need one battery and you may not use the spare for years, a name brand is worth the small extra cost.

Frequently Asked Questions

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

No. CR2032, CR2025, and CR2016 are different thicknesses, and using the wrong one will cause poor contact or not fit at all. The fob will not work reliably. Always use the exact type your fob needs.

Which side of the battery goes up?

The positive side (marked with a +) goes up, facing toward the inside of the fob case. Look at how the old battery was sitting before you remove it, and put the new one in the same direction.

How long does a 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 use your fob many times a day, the battery may only last two years. Heavy use drains it faster than occasional use.

What if I drop the battery and cannot find it?

Coin cell batteries are small and straightforward to lose. If you drop one, look on the floor around where you were working and check your clothes. If you cannot find it, just buy a new one — they cost a few dollars. Do not try to install a battery you cannot see clearly, or you may put it in upside down.

Is it safe to replace the battery myself?

Yes. The battery is not dangerous and there is no electrical risk. The only risk is breaking the plastic case if you pry too hard, so take your time opening it. If you are not comfortable opening the fob, your car's dealership can do it for you, usually for 10 to 20 dollars plus the cost of the battery.