Most key fobs use a coin-cell battery, usually CR2032 or CR2025
The battery in your key fob is almost certainly a coin-cell battery — a small, flat, round battery about the size of a dime. The most common type is the CR2032, which is 20 millimeters across and 3.2 millimeters thick. The second most common is the CR2025, which is the same width but slightly thinner at 2.5 millimeters. Some older or compact fobs use CR2016 (even thinner) or the larger CR2477.
You can find the exact battery your fob needs in three ways: check the owner's manual for your car, look inside the fob itself (many have the battery type printed on the case or battery compartment), or ask your car dealer or a local battery shop. The cost is usually between $3 and $8 per battery, and they last two to four years depending on how often you use the fob.
The letters and numbers tell you what you are buying. The "CR" means it is a lithium coin cell. The first two digits (20, 20, 20, or 24) refer to the diameter in millimeters. The last two digits (32, 25, 16, or 77) refer to the thickness in tenths of a millimeter. So CR2032 is 20 mm wide and 3.2 mm thick.
Key Takeaways
- CR2032 is the most common key fob battery, and you can check your manual or open your fob to confirm which type yours needs.
- Coin-cell batteries cost $3 to $8 and are sold at pharmacies, grocery stores, hardware stores, and online retailers.
- You can replace the battery yourself by opening the fob (usually with a coin or small screwdriver), removing the old battery, and sliding in the new one with the positive side facing up.
- If your fob stops working after a new battery, the problem is usually a dirty contact or a worn-out fob circuit, not the battery itself.
Where to buy the right battery
Coin-cell batteries are sold almost everywhere. Pharmacies like CVS and Walgreens stock them in the health and beauty section or near the checkout. Grocery stores, hardware stores, and big-box retailers like Target and Walmart carry them. You can also order them online from Amazon, eBay, or battery specialty sites.
When you buy, bring the old battery with you or write down the exact model number (CR2032, for example). Some stores sell them individually for $5 to $8, and some sell multipacks of four or eight for $10 to $15 — the multipack is better value if you have multiple fobs or devices that use the same battery.
Do not buy the cheapest option you find. Coin-cell batteries vary in quality. Panasonic, Energizer, Duracell, and Maxell are reliable brands. Off-brand batteries sometimes fail faster or hold less charge. The difference in price is usually $1 or $2, and a good battery will outlast a cheap one by months.
How to open your fob and replace the battery
Most key fobs open in one of two ways. The first is a slot or seam around the edge: slide a coin (a penny or dime works) or a flat-head screwdriver into the slot and twist gently to pry the two halves apart. The second is a small screw on the back or inside the battery compartment: use a small Phillips or flat-head screwdriver to remove it, then lift off the back cover.
Once the fob is open, you will see the battery sitting in a metal holder or slot. Note which side is facing up — the positive side (marked with a + or a flat surface) should face toward you. Gently pry out the old battery with your fingernail or a plastic tool (do not use metal, which can damage the circuit). Slide the new battery in with the positive side facing the same direction as the old one was facing.
Close the fob by pressing the two halves together until they click, or by replacing and tightening the screw. Test the fob by pressing each button and listening for the lock or unlock sound from your car. If it works, you are done. If it does not, try flipping the battery over — you may have installed it upside down — or clean the metal contacts inside the fob with a dry cloth.
Why your fob might not work even with a new battery
If you installed a new battery and the fob still does not work, the battery is usually not the problem. The most common culprit is dirty or corroded contacts inside the fob. Over time, moisture and dust build up on the metal contacts that touch the battery. When this happens, the circuit cannot complete even with a fresh battery.
To clean the contacts, open the fob again and look at the metal strips or dots inside. Dampen a cotton swab with rubbing alcohol and gently wipe each contact. Let it dry for a minute, then close the fob and test it. This fixes the problem in most cases.
If cleaning does not work, the circuit board inside the fob may be damaged or worn out. This is not something you can fix at home. Your car dealer can reprogram or replace the fob, usually for $150 to $400 depending on your car model. Some independent locksmiths also offer this service for less.
How long a coin-cell battery lasts
A CR2032 or CR2025 battery in a key fob typically lasts two to four years. The exact length depends on how often you use the fob. If you press the buttons dozens of times a day, the battery will drain faster. If you use it only a few times a day, it will last longer.
You will notice the fob starting to fail before the battery is completely dead. The range will shrink — you will have to stand closer to your car for the lock or unlock to work. The buttons may feel less responsive. When this happens, it is time to replace the battery, even if the fob still works from a few feet away.
Some fobs have a low-battery indicator light on the dashboard, though this is rare. Most do not, so you have to notice the range shrinking or the buttons becoming sluggish. Replacing the battery before it dies completely helps you avoid being locked out of your car.
Storing spare batteries and disposing of old ones
If you buy a multipack of coin-cell batteries, store them in a cool, dry place away from metal objects. Do not leave them loose in a drawer where they might touch coins or keys — this can cause them to discharge or short-circuit. A plastic battery organizer or a small container works well.
When you remove an old battery from your fob, do not throw it in the trash. Coin-cell batteries contain lithium and other materials that should not go to a landfill. Most pharmacies and retailers that sell batteries also accept old batteries for recycling — ask at the customer service desk. You can also search for a battery recycling location near you on the Call2Recycle website or your city's waste management page.
Frequently Asked Questions
Can I use a different battery type if I cannot find the exact one?
No. Using the wrong battery type can damage your fob or cause it to malfunction. The voltage and size matter — a CR2025 is not the same as a CR2032, even though they look similar. Always use the exact type your fob needs. If you cannot find it locally, order it online rather than substituting.
Do I need to reprogram my fob after changing the battery?
No. Replacing the battery does not erase the fob's programming. It will work when ready after you close the fob and test it. Reprogramming is only necessary if you buy a new fob or if the old one stops responding to the programming buttons.
What if the battery compartment is sealed and I cannot open it?
Some luxury car fobs have sealed compartments that are not meant to be opened by the owner. If you cannot find a seam or screw after looking carefully, take the fob to your car dealer or a locksmith. They have tools to open it safely without damaging the circuit board inside.
Is it normal for my fob to stop working right after I replace the battery?
No, and it usually means the battery is installed upside down or the contacts are dirty. Open the fob again, flip the battery so the positive side faces the other direction, and test it. If that does not work, clean the metal contacts with a dry cloth or rubbing alcohol and try again.
Can I use rechargeable batteries in my key fob?
Rechargeable coin-cell batteries exist, but they are not recommended for key fobs. They have lower voltage than standard lithium batteries and may not provide enough power for reliable operation. Stick with standard CR2032 or CR2025 batteries — they are cheap and last long enough that recharging is not worth the hassle.