Most car fob batteries last three to four years and cost $3 to $10 to replace
You can replace a car key fob battery yourself in about five minutes using a coin and a fresh battery from any drugstore or supermarket. The battery type varies by fob model—usually CR2032, CR2025, or CR2016—but you can find the right one by checking your owner's manual or taking the fob apart to see what's inside. The hardest part is not losing the small metal contacts or spring while the fob is open.
Most fobs use a coin-slot seam running around the edge. Insert a flat coin (a dime or penny works) into the slot and twist gently until the two halves separate. Some fobs have a small button or latch on the back instead—press or slide it to pop the case open. Once the fob is apart, note which side the battery sits on and which direction it faces (the + side usually points up), then lift it out and replace it with a new one of the same type.
Key Takeaways
- Most car fob batteries are CR2032, CR2025, or CR2016 and cost between $3 and $10 at any pharmacy or grocery store.
- Open the fob by inserting a coin into the seam around the edge and twisting gently, or by pressing a release button on the back.
- Note the battery type and which direction it faces before removing it, so you install the new one the same way.
- After inserting the new battery, snap the fob halves back together and test all buttons before putting it away.
- If the fob still does not work after a new battery, the problem is likely a worn contact or broken circuit board, not the battery itself.
Finding the right battery type for your fob
The easiest way to know which battery your fob needs is to check your vehicle's owner's manual—it usually lists the battery type in the key fob section. If you do not have the manual, you can open the fob and look at the battery itself; the type is printed on the metal surface. Take a photo of it with your phone so you have the number when you go to the store.
If you want to know before opening the fob, search online for your vehicle's year, make, and model plus "key fob battery." Most common types are CR2032 (the most frequent), CR2025, and CR2016. All three are coin-cell batteries about the size of a dime and cost roughly the same. Pharmacies, grocery stores, hardware stores, and online retailers all stock them. Buy one or two extras—they last years in storage and are cheap enough to keep on hand.
Opening the fob without breaking it
Look at the seam running around the edge of your fob. This is where the two plastic halves meet. Insert a flat coin—a dime, penny, or flathead screwdriver—into the seam and explore gentle, steady pressure as you twist. You are not trying to pry it apart forcefully; you are rotating the coin to separate the two halves. The fob should pop open after a quarter-turn or so.
Some fobs have a small button or slot on the back instead of a seam. Press the button or slide the latch, and the battery cover will pop off or the halves will separate. If you feel strong resistance, stop and look for a button or latch you may have missed. Forcing a fob that does not want to open can crack the plastic or break the circuit board inside.
Once the fob is open, you will see the battery sitting in a small metal holder or slot. The holder usually has two metal contacts—one on each side of the battery. Do not touch these contacts with your bare fingers if you can help it; oils from your skin can interfere with the connection. If you do touch them, wipe them clean with a dry cloth before closing the fob.
Removing and replacing the battery
Before you remove the old battery, take a moment to note which side faces up. Most batteries have a + symbol on the top side and a − symbol on the bottom. The + side should face up toward the top of the fob. If you install the new battery upside down, the fob will not work, so this detail matters.
Gently lift the old battery out of its holder. If it is stuck, use a plastic spoon handle or a plastic pry tool—not metal, which can damage the contacts. Once it is out, drop the new battery into the same spot with the + side facing the same direction as the old one faced. The battery should sit flat and snug in the holder. If it is loose or tilted, remove it and try again.
Do not force the battery into place. If it does not fit easily, you may have the wrong battery type. Double-check the number on the old battery and make sure the new one matches. If the numbers are the same and it still will not fit, the holder itself may be bent or damaged, and the fob may need professional service.
Closing the fob and testing it
Align the two halves of the fob so the seams match up evenly. Press them together firmly until you hear or feel a click. If the fob has a battery cover rather than two halves, slide or snap the cover back into place. The fob should feel solid and not rattle when you shake it gently.
Test each button on the fob—lock, unlock, panic, trunk, or whatever buttons yours has. Point the fob at your car from a few feet away and press each button. You should see the car's lights flash or hear the locks engage. If nothing happens, open the fob again and check that the battery is seated properly and facing the right direction. If the battery is in correctly and the buttons still do not work, the problem is likely a worn contact or a broken circuit board, not the battery.
What to do if the fob still does not work
If you installed a fresh battery and the fob is still dead, the issue is usually one of three things: the battery is not making contact with the metal holders, the metal contacts are corroded or worn, or the circuit board inside is damaged.
Start by opening the fob again and inspecting the metal contacts. They should be shiny and clean. If they look dark, dull, or crusty, they may be corroded. Gently rub them with a clean, dry cloth or a pencil eraser to remove the corrosion. Then reinstall the battery and test again.
If the contacts are clean and the battery is seated correctly but the fob still does not work, the circuit board or button contacts inside are likely damaged. This is not something you can fix at home. Contact your car's dealership or a local locksmith for a replacement fob. Dealerships usually charge $150 to $400 for a new fob, depending on the vehicle. Some locksmiths offer the same service for less, so it is worth calling around.
Storing batteries and fobs safely
Keep spare batteries in a cool, dry place away from metal objects that could short-circuit them. A small plastic container in a kitchen drawer works well. Do not store batteries in a car, especially not in direct sunlight or near heat sources, because temperature swings can shorten their life.
If your fob will sit unused for more than a few months—say, if you have a spare fob you do not use often—consider removing the battery to prevent it from draining or leaking. Batteries left in unused devices can corrode the contacts over time. When you need the fob again, install a fresh battery and it will work like new.
Frequently Asked Questions
Can I use any CR2032 battery, or does the brand matter?
Any CR2032 battery will work, but name brands like Duracell, Energizer, and Panasonic tend to last longer than generic store brands. The difference is usually a few months of life, not worth a big price jump. Buy whatever is on sale, but if your fob dies unexpectedly, try a name brand next time.
What if I lose a small metal spring or contact when the fob is open?
If you lose a spring or contact, the fob will not work until you replace it. Take the fob to a dealership or locksmith—they can order the part and install it, usually for $20 to $50 plus the cost of the part. Do not try to glue or tape a lost contact back in place; it will not conduct electricity properly.
How long does a new battery last in a car fob?
Most car fob batteries last three to four years under normal use. If you use the fob heavily—pressing the buttons many times a day—the battery may wear out in two to three years. If you use it lightly, it may last five years or more.
Why does my fob work sometimes but not other times?
Intermittent fob problems usually mean the battery is dying or the contacts are corroded. Try a new battery first. If that does not fix it, open the fob and clean the metal contacts with a dry cloth. If the problem persists, the circuit board or button contacts are likely worn, and you will need a replacement fob.
Can I replace the battery in a fob that is water-damaged?
If your fob got wet, let it dry completely for at least 24 hours before opening it. Once it is dry, open it and check for corrosion on the contacts and circuit board. If you see white or green crusty buildup, gently clean it with a dry cloth or pencil eraser. A new battery may restore function, but water damage often ruins the circuit board permanently, so a replacement fob may be necessary.