Most key fobs use a coin-cell battery you can swap yourself in under two minutes
You can change your key fob battery without tools or a trip to the dealer. The battery is almost always a coin-cell type — a flat, round battery the size of a dime or nickel — and it sits in a compartment you can open by hand or with a flathead screwdriver. The whole job takes longer to find the right battery than to install it.
The hardest part is knowing which battery your fob needs. The battery type is printed on the old battery itself, or stamped inside the fob compartment. Common types are CR2032, CR2025, and CR2016. Once you have the right battery, the swap is straightforward: open the fob, remove the old battery, drop in the new one with the positive side facing up, and close it.
Key Takeaways
- Coin-cell batteries for key fobs cost $3 to $8 and are sold at drugstores, supermarkets, and hardware stores without any special purchase requirements.
- The battery type is printed on the old battery or stamped inside the fob case, so check there first before buying a replacement.
- Most fobs open by sliding a small lever, prying a seam with a flathead screwdriver, or unscrewing a single screw on the back.
- The positive side of the battery (marked with a +) must face upward when you install it, or the fob will not work.
- If the fob still does not work after a new battery, the problem is usually a corroded contact or a broken button, not the battery itself.
Find out what battery your fob uses
Before you buy a replacement, identify the battery type. Remove the old battery from your fob and look at the top surface — the battery type is stamped there in a code like CR2032 or CR2025. Write down this code or take a photo.
If the old battery is dead or missing, look inside the fob compartment itself. Many fobs have the battery type printed on the plastic case. If you cannot find it there, check your vehicle's owner manual or search online for your specific fob model number (usually printed on the back of the fob).
Once you know the type, buy the replacement at any drugstore, supermarket, or hardware store. These batteries are inexpensive and widely stocked. Do not buy a generic "key fob battery" — the specific type matters.
Open the fob without damaging the case
Key fobs open in three common ways. The most frequent is a small lever or slot on the edge of the fob that you slide or pry to separate the two halves. Look around the seam where the front and back meet — you will usually see a small notch or line.
If there is no lever, use a flathead screwdriver to gently pry the seam open. Start at one corner and work your way around, explore steady pressure rather than force. The two halves will separate with a small click. Do not pry hard or you risk cracking the plastic.
A few fobs have a small screw on the back. Unscrew it with a Phillips or flathead screwdriver (depending on the screw type), then the back cover will lift off. 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.
Remove the old battery and install the new one
Gently lift the old battery out of its compartment. If it is held by a metal clip, lift the clip slightly and slide the battery out from underneath. Do not force it — if it is stuck, the clip may be bent and you should straighten it carefully with a small flathead screwdriver.
Before you install the new battery, check the compartment for corrosion. If the metal contacts inside look dark, green, or crusty, wipe them clean with a dry cloth or a cotton swab. Corrosion prevents the battery from making good contact and is a common reason fobs stop working even with a fresh battery.
Place the new battery into the compartment with the positive side (marked with a +) facing upward. The negative side (marked with a −) should face down toward the circuit board. Slide it under the metal clip if there is one. The battery should sit flat and not wobble.
Close the fob and test it
Press the two halves of the fob back together until they click. If your fob had a screw, replace it now. Do not overtighten — just snug enough that it does not rattle.
Test the fob by pressing each button while standing near your vehicle. You should see the lights flash or hear the door lock and unlock. If nothing happens, open the fob again and check that the battery is seated properly and the positive side is facing up. Also look at the metal contacts — if they are still corroded, clean them again with a dry cloth.
If the fob still does not work after you have checked the battery and contacts, the problem is likely a broken button or a damaged circuit board, not the battery. In that case, you will need to have the fob repaired or replaced by a dealer or a locksmith.
Common mistakes that prevent the fob from working
The most frequent error is installing the battery upside down. The positive side must face up. If you installed it and the fob did not work, open it again and flip the battery over.
The second mistake is not cleaning corroded contacts. If the metal inside the fob looks discolored, wipe it with a dry cloth or a cotton swab before you install the new battery. Corrosion acts like a wall between the battery and the circuit board, and a new battery will not help if the contacts are dirty.
A third error is buying the wrong battery type. CR2032, CR2025, and CR2016 look almost identical but are not interchangeable. Always check the code on the old battery or inside the fob case before you buy a replacement.
Finally, do not force the fob open or closed. If it is not opening easily, you may be prying in the wrong spot. Look for a small lever or slot along the seam. If you force it, you can crack the plastic and make the fob unusable.
When to replace the whole fob instead of just the battery
If you have installed a fresh battery, cleaned the contacts, and the fob still does not work, the problem is inside the fob itself. The circuit board may be damaged, or one of the rubber buttons may have worn through. In these cases, replacing the battery will not help.
A new fob from a dealer or locksmith costs $100 to $400 depending on your vehicle, but a replacement battery costs only $3 to $8. It is always worth trying a new battery first. If that does not work, then you know the fob needs repair or replacement.
Some vehicles allow you to program a new fob yourself using a sequence of key turns in the ignition. Check your owner manual to see if your vehicle supports this. If not, a locksmith or dealer can program a new fob for you, usually in under an hour.
Frequently Asked Questions
Can I use any coin-cell battery, or does it have to be the exact type?
It has to be the exact type. CR2032, CR2025, and CR2016 are not interchangeable — they have different thicknesses and voltages. Using the wrong type can damage the fob or cause it to malfunction. Always check the code on the old battery or inside the fob case.
What if I cannot get the fob open?
Look for a small lever or slot along the seam where the two halves meet. If you see one, slide or pry it gently. If there is no lever, try a flathead screwdriver at different points along the seam — one spot will give way more easily than others. If you still cannot open it, check your owner manual or search online for your specific fob model.
The battery is stuck and will not come out. What do I do?
Do not force it. The metal clip holding the battery may be bent or corroded. Use a small flathead screwdriver to gently lift the clip, then slide the battery out from underneath. If it is still stuck, try cleaning around the edges with a dry cloth to remove any corrosion or debris.
My fob worked for a few days after I put in a new battery, then stopped. Why?
The battery may have been installed upside down, or the contacts inside the fob may be corroded. Open the fob again and check that the positive side of the battery is facing up. Also wipe the metal contacts with a dry cloth. If the fob still does not work, the circuit board may be damaged.
Do I need to reprogram my fob after changing the battery?
No. Changing the battery does not erase the fob's programming. Once you install the new battery and close the fob, it should work when ready without any reprogramming.