Most fob batteries are coin-cell types you can swap yourself in under five minutes
A dead key fob battery is one of the easiest car maintenance jobs you can do at home. The battery inside is almost always a coin-cell type — a flat, round battery about the size of a dime or nickel — and you can replace it without tools or a trip to the dealer. The whole job takes less than five minutes, costs between $3 and $8 for the battery, and requires nothing but the fob itself and the replacement battery.
The hardest part is usually figuring out how to open the fob case, since different manufacturers use different designs. Once you know which type you have, the rest is straightforward.
Key Takeaways
- Most car key fobs use a CR2032, CR2025, or CR2016 coin-cell battery that you can buy at any drugstore, supermarket, or hardware store for a few dollars.
- Fobs open either by prying a seam with a flat tool, sliding a button or lever, or unscrewing a small screw on the back — check your owner's manual or look for a slot or line on the case to identify which type yours is.
- When you open the fob, note which side of the battery faces outward before you remove it, because the new battery must go in the same way.
- If your fob still does not work after you install a new battery, the problem is likely a worn contact or a dead circuit board, not the battery itself.
Identify your fob type and find the battery size
Before you buy a replacement battery, you need to know which type of battery your fob uses. The easiest way is to check your owner's manual — search for "key fob battery" or "remote battery" in the index. The manual will tell you the exact model number, usually something like CR2032, CR2025, or CR2016.
If you do not have the manual, you can open the fob and look at the battery itself. The model number is printed on the flat side. Once you know the number, you can buy the replacement at a pharmacy, supermarket, or hardware store. These batteries are common and inexpensive — you should find them near the watch batteries or in the electronics aisle.
Do not guess at the size. A CR2032 and a CR2025 look almost identical but have different thicknesses, and using the wrong one can cause the fob to not close properly or the battery to lose contact.
Open the fob case
There are three common ways fobs open. Look at your fob and identify which one matches yours before you start.
Pry-open design: Look for a thin seam or slot running around the edge of the fob. Use a flat tool — a coin, a butter knife, a flathead screwdriver, or a plastic pry tool — and gently work it into the seam. Twist slightly to separate the two halves. Start at one corner and work your way around if it does not pop open when ready. Be gentle; the plastic can crack if you force it.
Slide-open design: Some fobs have a button or lever on the side or back that you push or slide to release the battery cover. Look for a small arrow or marking that shows the direction to move it. Push or slide in that direction until the cover pops off or slides away.
Screw-open design: A few fobs have a small screw on the back. Use a screwdriver that fits the screw head snugly — a screwdriver that is too large or too small will strip the screw. Remove the screw and set it somewhere safe so you do not lose it. Then gently pry the two 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 side with the + symbol or the side that is blank. This matters because the battery must go back in the same way.
If the battery is loose, you can straightforward lift it out with your finger. If it is held in place by a metal clip or spring, gently lift or pry the clip away from the battery first, then remove the battery. Do not force it; if it feels stuck, check that you have released any clips.
Once the old battery is out, you can throw it away. Do not leave it sitting on a metal surface or near other batteries, as it can cause a short circuit.
Install the new battery
Take your new battery and place it in the same position as the old one — with the same side facing up. If the old battery had the + symbol facing up, the new one should too. If the old battery was blank-side up, the new one should be blank-side up.
Gently press the battery down into the holder until it sits flat. If there is a metal clip or spring, make sure it is resting on top of the battery. The battery should not move around when you gently shake the fob.
Close the fob case by reversing whatever you did to open it. If you pried it open, press the two halves together until they click. If you slid a cover, slide it back into place. If you removed a screw, replace it and tighten it snugly — not so tight that you strip it, but tight enough that it does not rattle.
Test the fob and troubleshoot if needed
Stand near your car and press a button on the fob. You should see the lights flash or hear the locks click. If nothing happens, try pressing the button several 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 sitting flat in its holder and that the metal contacts are clean. If they look dirty or corroded, gently wipe them with a dry cloth or a pencil eraser, then reinstall the battery.
If the fob works for a few seconds and then stops, or if it only works when you press the button hard, the problem is likely worn contacts or a failing circuit board inside the fob, not the battery. At that point, you will need to have the fob repaired or replaced by a dealer or a locksmith.
When to replace the entire fob instead
If you have replaced the battery and the fob still does not work, and the contacts look clean, the circuit board inside the fob may be damaged. This is not something you can fix at home. A locksmith or car dealer can reprogram a new fob to your car, though the cost varies widely depending on your vehicle — anywhere from $50 to $300 or more.
Before you buy a new fob, try the battery in a different fob if you have one (like a spare). If the spare fob works with the new battery, your original fob is dead and needs replacement. If the spare fob also does not work with the new battery, the problem is your car's receiver, not the fobs, and you should have a dealer check it.
Frequently Asked Questions
What if I cannot find the right battery size?
Take the old battery to a pharmacy or electronics store and show it to the staff. They can match it by sight. You can also search the model number (like CR2032) online to confirm the size before you buy. Do not guess — using the wrong size can damage the fob or cause it to malfunction.
Can I use a rechargeable battery in my key fob?
No. Rechargeable batteries have a different voltage and chemistry than standard coin-cell batteries, and they can damage the fob's circuit board or cause the fob to stop working. Always use a fresh, non-rechargeable battery of the correct model number.
How often do I need to replace the fob battery?
Most fob batteries last three to four years with normal use. If you use your fob heavily — pressing the buttons many times a day — the battery may wear out sooner. You will know it is time when the fob only works from very close to the car or when you have to press the button multiple times.
Is it safe to open my key fob myself?
Yes, opening a key fob to replace the battery is safe and does not void any warranty. The battery compartment is sealed and contains no hazardous materials. Just be gentle when prying the case open so you do not crack the plastic.
What should I do with the old battery?
Most coin-cell batteries can go in the regular trash, but some communities have battery recycling programs. Check your local waste management website to see if they accept batteries. If you have a lot of old batteries, a pharmacy or electronics store often has a battery recycling bin near the checkout.