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

A dead key fob battery is one of the easiest car problems to fix at home. You do not need tools beyond a coin, the replacement battery costs between $3 and $8, and the whole job takes about five minutes. The battery type your fob needs is printed on the back or inside the case — usually CR2032, CR2025, or CR2016 — and any pharmacy, grocery store, or dollar store stocks them.

The only real decision is whether to pry the fob open yourself or have a dealer or locksmith do it. Prying it open yourself carries almost no risk if you use a coin instead of a screwdriver, and you will save the $15 to $50 a shop would charge. This guide walks you through the self-service route step by step.

Key Takeaways

  • The battery type is printed on the back of your fob or visible when you open it — common types are CR2032, CR2025, and CR2016.
  • You need only a coin (dime or penny works) and a replacement battery from any pharmacy or grocery store.
  • Insert the coin into the slot on the fob's edge and twist gently to separate the two halves, then swap out the old battery for the new one.
  • If your fob has a screw instead of a slot, use a small flathead screwdriver, but avoid forcing it if the fob resists.
  • After closing the fob, test it by pressing each button to confirm the new battery is working before you leave the store or pharmacy.

Locate the battery type before you buy a replacement

The easiest way to find out which battery your fob needs is to look at the back of the case. Most fobs have the battery model number printed there — CR2032 is by far the most common, but you may also see CR2025, CR2016, or occasionally a different type. If the number is not printed on the back, you can open the fob first and check the battery itself, which will have the model number stamped on it.

Once you know the type, buy one replacement battery. A single battery costs $3 to $8 depending on the brand and where you shop. Pharmacies like CVS and Walgreens, grocery stores, and dollar stores all stock common types in their pharmacy or electronics section. You do not need a premium brand — a generic CR2032 works just as well as a name-brand one.

Open the fob by finding the slot or screw on the edge

Look at the thin edge where the two halves of the fob meet. Most fobs have a small slot cut into this edge — it looks like a thin line running horizontally. A few fobs have a tiny screw instead. If you see a slot, you will use a coin. If you see a screw, you will use a small flathead screwdriver.

For a slot: Insert a coin (a dime or penny works fine) into the slot and twist it gently, as if you were opening a paint can. You are not trying to force the fob apart — just explore steady, gentle pressure. The two halves should separate with a small click. If it does not budge after a few seconds of gentle twisting, stop and try a different angle or a different coin. Forcing it risks cracking the plastic.

For a screw: Use a small flathead screwdriver that fits snugly into the screw head. Turn it counterclockwise slowly. Once the screw is loose enough, you can usually remove it by hand. Keep the screw somewhere safe so you do not lose it — you will need it to close the fob again.

Remove the old battery and insert the new one

Once the fob is open, you will see the battery sitting in a small compartment, usually held in place by a metal clip or spring on one side. The battery is a flat, round disc. Note which side is facing up — the positive side (marked with a + symbol) should face toward you or toward the top of the fob, depending on the design.

Gently pry the old battery out using your fingernail or the edge of the coin. If the battery is stuck, wiggle it slightly side to side rather than pulling straight up. Once it is out, place the new battery in the same compartment with the positive side facing the same direction as the old one. The battery should sit flat and fit snugly without forcing.

Close the fob and test it before you leave

For a slot-opening fob: Line up the two halves so they sit flush against each other, then press them together firmly. You should hear or feel a small click as they lock. If they do not click, the battery may not be seated correctly — open it again and check that the battery is sitting flat in its compartment.

For a screw-opening fob: Line up the two halves and insert the screw back into its hole. Turn it clockwise with your screwdriver until it is snug. Do not overtighten — you only need it tight enough that the fob does not rattle.

Once the fob is closed, press each button (lock, unlock, trunk, panic) to confirm the new battery is working. If nothing happens, open the fob again and check that the battery is facing the right direction. If the buttons work, you are done — the battery should last three to four years before you need to replace it again.

What to do if the fob still does not work after replacing the battery

If you replaced the battery and the fob still does not respond, the problem is usually one of three things: the battery is facing the wrong direction, the battery is not making good contact with the metal clip, or the fob has a deeper problem unrelated to the battery.

Start by opening the fob again and checking that the positive side of the battery faces the correct direction. Look at the metal clip or spring — it should be touching the battery firmly. If the clip is bent or loose, gently bend it back so it presses against the battery. Close the fob and test again.

If the fob still does not work, the issue may be a broken button contact, water damage, or a circuit problem inside the fob. At that point, a locksmith or car dealer can diagnose it, though replacing the entire fob is often cheaper than repairing an old one. Many dealers charge $200 to $400 for a new fob, while aftermarket fobs from online retailers run $50 to $150 and can be programmed by a locksmith for an additional $50 to $100.

Frequently Asked Questions

Can I use any battery type, or does it have to match the model number?

You must use the exact model number printed on your fob or the old battery. CR2032, CR2025, and CR2016 are all different sizes and voltages, and using the wrong one can damage the fob's circuit or straightforward not fit in the compartment. If you are unsure which type you need, take a photo of the number and show it to the pharmacy staff.

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 faster. Cold weather can also temporarily reduce battery performance, though the battery usually works again once it warms up.

What if I lose the screw when I open the fob?

If you lose a screw, you can buy a replacement at a hardware store for less than a dollar. Bring the fob with you so the staff can match the size. Alternatively, some locksmiths keep spare fob screws and can install one for you, usually for $10 to $20.

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

Replacing the battery yourself is safe and carries no risk to you or the fob if you use a coin instead of a screwdriver and do not force the case open. The only reason to go to a dealer is if you are uncomfortable opening the fob or if the fob is still under warranty and you want to avoid voiding it — though most warranties do not cover battery replacement.