Open the key fob carefully to reach the battery

Most key fobs split into two halves along a seam that runs around the edge. Look for a small slot or notch on the side — this is where you insert a flat tool to pry the case open. A coin, butter knife, or flathead screwdriver works well. Insert the tool gently into the slot and twist slightly to separate the two halves. Do not force it; if it does not budge, try a different spot along the seam.

Once the fob opens, you will see the battery sitting in a plastic holder, usually in the center. The battery is round and flat, about the size of a dime or larger depending on your fob model. Note which side faces up — the positive side (marked with a + symbol) should face toward you. Take a photo with your phone before you remove anything, so you remember the correct orientation when you put the new battery in.

Key Takeaways

  • Key fobs typically split along a seam using a flat tool like a coin or screwdriver inserted into a small notch.
  • The battery sits in a plastic holder inside the fob, and you must note which side faces up before removing it.
  • Common key fob batteries are CR2032, CR2025, or CR2016 — check your old battery or your car's manual to buy the right replacement.
  • Insert the new battery with the positive side facing up, close the fob halves firmly until you hear a click, and test the buttons before you leave.
  • If the fob still does not work after a new battery, the problem may be a broken button contact or water damage inside the case.

Remove the old battery and note the model number

Gently lift the battery out of its holder using your fingernail or the edge of a plastic tool. Do not use a metal tool directly on the battery, as this can damage it or cause a short circuit. Once the battery is out, look at the top surface. You will see a code printed on it — something like CR2032, CR2025, or CR2016. Write this number down or take a photo. This is the model you need to buy as a replacement.

If the number is hard to read or worn away, check your car's owner manual or search online for your specific key fob model. The manual usually lists the battery type in the section on key fob maintenance. You can also ask at an auto parts store or pharmacy — they carry common key fob batteries and can often identify the right one if you bring the fob with you.

Buy the correct replacement battery

Key fob batteries are inexpensive and widely available. You can find them at auto parts stores (AutoZone, O'Reilly, Advance Auto Parts), pharmacies (CVS, Walgreens), grocery stores, and online retailers. A single battery usually costs between one and three dollars. Buy one or two extras while you are at it — key fob batteries last two to four years, and having a spare on hand saves a trip later.

When you buy the battery, check the package to confirm it matches the model number you wrote down. The package will show the code (CR2032, for example) clearly on the front. Some batteries are labeled by voltage (3V) instead of model number, so check both if you are unsure. If you are buying online, verify the seller ships quickly, since you will want to test the new battery as soon as possible.

Insert the new battery with the correct orientation

Before you open the new battery package, wash your hands or wipe them dry. Oils from your skin can interfere with the battery contact. Remove the battery from the package and look at both sides. One side is flat and marked with a + symbol (positive); the other side is slightly raised and unmarked (negative). The positive side must face up toward the button contacts inside the fob.

Place the new battery into the holder in the same position as the old one was. If you took a photo earlier, use it as a reference. Press down gently until the battery sits flat in the holder. You should feel it settle into place. Do not force it or bend the battery holder. If the battery does not sit flat, remove it and check that the holder is clean and free of debris.

Close the fob and test all the buttons

Align the two halves of the fob so the seam matches up evenly. Press them together firmly until you hear or feel a click. The fob should close completely with no gaps. If it does not close all the way, open it again and check that the battery is sitting flat and that no wires or plastic tabs are in the way.

Once the fob is closed, test every button — lock, unlock, trunk, panic, or any others your fob has. Press each button several times and listen for the click or beep from your car. If the car responds normally, the battery change is complete. If some buttons work and others do not, the problem may be a worn contact inside the fob rather than the battery. If no buttons work, double-check that the battery is inserted with the positive side facing up.

What to do if the new battery does not fix the problem

If you installed a fresh battery and the fob still does not work, the issue is likely inside the fob itself. The most common cause is corrosion or wear on the metal contacts that the battery touches. These contacts can become dirty or damaged over time, especially if the fob has been exposed to moisture. Open the fob again and look at the metal contacts — they should be shiny. If they look dark, dull, or corroded, gently clean them with a dry cotton swab or a pencil eraser.

Another possibility is that water has gotten inside the fob and damaged the circuit board or button contacts. If you have dropped the fob in water or spilled liquid on it, leave it open in a warm, dry place for 24 to 48 hours to dry completely. Do not use heat or a hair dryer, as this can damage the plastic. If the fob still does not work after drying, the circuit board may be permanently damaged, and you will need to replace the entire fob.

Prevent battery problems by storing your fob correctly

Key fob batteries last longer when the fob is kept dry and away from extreme heat or cold. Do not leave your fob in direct sunlight, in a hot car, or in a freezing garage for extended periods. Keep it in a pocket or bag at room temperature. Avoid dropping the fob or exposing it to water, as moisture can corrode the battery contacts and damage the circuit board inside.

If you notice the buttons becoming sluggish or unresponsive before the battery is completely dead, that is a sign the battery is weakening. Replace it right away rather than waiting for the fob to stop working entirely. A fresh battery takes only a few minutes to install and costs very little, so there is no reason to put up with a fading fob.

Frequently Asked Questions

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

No — always use the exact model listed on your old battery or in your manual. Different models have different voltages and sizes, and using the wrong one can damage the fob or cause it to malfunction. If your local store does not have the model in stock, order it online or ask the store to order it for you.

What should I do with the old battery?

Do not throw it in the trash. Most retailers that sell batteries also accept old ones for recycling. Take your old battery back to the store where you bought the new one and ask where the recycling bin is. Many pharmacies and auto parts stores have a battery recycling program at the checkout counter.

Why is my key fob still not working after I changed the battery?

The most common reason is that the battery is installed upside down — the positive side must face up. Open the fob and check the orientation. If the battery is correct, the metal contacts inside may be dirty or corroded. Clean them gently with a dry cotton swab. If neither of these fixes the problem, water damage or a broken circuit board inside the fob may be the cause.

How often do I need to change my key fob battery?

Most key fob batteries last two to four years, depending on how often you use the fob. If you use your fob multiple times per day, the battery may wear out faster. If you notice the buttons becoming sluggish or the car not responding from as far away as it used to, the battery is weakening and should be replaced soon.

Can I change the battery myself, or do I need to go to a dealership?

You can change it yourself — the process takes only a few minutes and requires no special tools beyond a coin or screwdriver. A dealership can do it for you, but they will charge a service fee (usually ten to twenty dollars) on top of the battery cost. Changing it at home is much cheaper and just as effective.