You can replace most car key fob batteries yourself in under five minutes
A dead key fob battery is one of the easiest car problems to fix on your own. The battery inside is usually a coin-cell battery — a small, flat, round battery about the size of a dime — and you can buy a replacement at any drugstore, supermarket, or hardware store for a few dollars. The hardest part is often just opening the fob without breaking the plastic.
You do not need special tools, a mechanic, or a trip to the dealership. Once you know what battery your fob uses and how to open it, the swap takes minutes.
Key Takeaways
- Most car key fobs use a coin-cell battery, usually CR2032, CR2025, or CR2016, which you can buy at any pharmacy or grocery store for under $5.
- Check your owner's manual or search online for your specific car make, model, and year to find the exact battery type before you buy.
- Open the fob by finding the seam (usually on the side or back) and gently prying with a flat tool like a coin or flathead screwdriver.
- Note which side of the battery faces up before you remove it, then insert the new battery the same way and snap the fob closed.
- If the fob still does not work after replacing the battery, the problem may be a broken button contact or a dead fob circuit, not the battery.
Finding the right battery type for your fob
The battery type varies by car make and model. The most common types are CR2032, CR2025, and CR2016 — the numbers refer to the size and voltage. A CR2032 is slightly thicker than a CR2025, and both are more common than CR2016.
The fastest way to find your battery type is to check your owner's manual — search for "key fob battery" or "remote battery" in the index. If you do not have the manual, search online for "[your car year, make, model] key fob battery type." You can also call your car dealership's parts department and give them your vehicle identification number (VIN); they will tell you the battery type in seconds.
Once you know the type, buy the battery at a pharmacy, grocery store, or hardware store. You will usually find them in the watch or electronics section. A single battery costs $2 to $5. Some stores sell them in multipacks, which is useful if you have multiple fobs or want spares on hand.
How to open your key fob safely
The fob case is held together by a seam, usually running along the side or the back. Look closely at the edges — you will see a thin line where the two halves meet. This is where you pry.
Use a flat tool: a coin, a flathead screwdriver, or a plastic pry tool. Start at one end of the seam and gently push the tool into the gap. Do not force it — the plastic is thin and breaks easily. Rock the tool slightly to widen the gap, then move along the seam. Once the gap is wide enough, you can usually pop the case open by hand.
Some fobs have a small notch or indent on the edge designed as a pry point. If you see one, start there. If your fob has a metal key blade attached, you may need to remove it first — usually it slides or twists out of a slot on the side.
Removing and replacing the battery
Once the fob is open, you will see the battery sitting in a small plastic holder. Before you touch it, look at which side faces up — the positive side (marked with a + symbol) or the negative side (usually blank or marked with a −). Take a mental note or take a photo with your phone.
Gently pry the old battery out of its holder using your fingernail or a plastic tool. Do not use a metal tool directly on the battery, as it can damage the contacts. Once the old battery is out, insert the new battery with the same side facing up. It should sit flat in the holder and click slightly when it is in place.
Close the fob by pressing the two halves together. You may hear a small click when the seams align. Press firmly around the edges to make sure it is fully closed, but do not force it — if it does not close smoothly, check that the battery is sitting flat and that no plastic is caught in the seam.
Testing your fob after replacement
Point the fob at your car and press each button — lock, unlock, trunk, panic, or whatever buttons your fob has. The car should respond when ready. If it does, the battery replacement worked.
If the fob still does not work, the problem is not the battery. The most common causes are a broken button contact (the rubber pad under the button has worn through) or a dead fob circuit board. In those cases, you will need to replace the entire fob, which you can order from a dealership or an online retailer, or have programmed by a locksmith.
When to replace the entire fob instead
If your fob is very old, cracked, or has buttons that stick or do not respond, replacing just the battery may not solve the problem. A new fob from a dealership typically costs $200 to $500, depending on the car. Aftermarket fobs from online retailers cost $30 to $150 and work with most cars, though some require programming by a locksmith or dealership.
If you have a spare fob, test it with your car before you buy a replacement. If the spare works, your original fob is broken and needs replacement. If the spare also does not work, the problem may be with your car's receiver, not the fob — in that case, contact your dealership.
Storing extra batteries and fobs
Keep a spare coin-cell battery in your car or at home so you can replace a dead fob without a trip to the store. Coin-cell batteries last for years when stored in a cool, dry place. Do not store them in direct sunlight or in a hot car, as heat shortens battery life.
If you have an older car with an original fob that is starting to fail, consider buying a replacement fob now while you still have time. Waiting until your fob completely dies leaves you locked out of your car, which is much more expensive to fix than replacing a fob on your own schedule.
Frequently Asked Questions
Can I use a different battery type if I cannot find the exact one?
No. Different coin-cell batteries have different voltages and sizes. Using the wrong battery can damage the fob's circuit board or not fit in the holder at all. Always use the exact type your fob requires.
What if I break the fob case while opening it?
If the plastic cracks but the fob still works, you can hold it together with a rubber band or electrical tape temporarily. If the crack is large or the fob stops working, you will need to replace the entire fob. Some locksmiths can repair cracked cases, though replacement is usually cheaper.
How often do key fob batteries need replacing?
Most coin-cell batteries last three to four years with normal use. If you use your fob frequently, the battery may die sooner. If you rarely use it, it may last longer. There is no set schedule — you replace it when it stops working.
Can I replace the battery in a smart key or push-button fob?
Yes, most smart keys and push-button fobs use the same coin-cell batteries as traditional fobs. The process is identical: find the seam, open the case, note the battery orientation, swap it out, and close the fob. Check your owner's manual to confirm the battery type.
What should I do with the old battery?
Coin-cell batteries contain small amounts of lithium and should not go in the trash. Most pharmacies and electronics stores have battery recycling bins near the checkout. You can also check Earth911.com or call your local waste management to find a recycling location near you.