Most car key fob batteries last three to four years and cost $3 to $10 to replace
A dead key fob battery is one of the easiest car problems to fix yourself. The battery inside your fob—usually a coin-cell battery like a CR2032, CR2025, or similar—wears out over time. When your buttons stop working or only work when you press hard, the battery is almost certainly dead. You can buy a replacement at any pharmacy, grocery store, or hardware store and swap it in without tools or a trip to the dealer.
The whole job takes about five minutes. You do not need special equipment, and there is almost no way to damage anything if you follow the steps in order. The only real risk is putting the battery in backwards, which straightforward means it will not work—you just flip it and try again.
Key Takeaways
- Coin-cell batteries like CR2032 cost $3 to $10 and are sold at pharmacies, grocery stores, and hardware stores without a receipt or membership.
- Most fobs open by sliding a small lever, pressing a hidden button, or prying a seam with a flat tool—check your owner's manual or search your fob model online if you are unsure which method yours uses.
- The battery sits in a metal holder with a plus sign (+) facing up; if it does not work after you install it, flip it over and try again.
- If the fob still does not work after a new battery, the problem is likely a broken button contact or water damage, not the battery itself.
Find out what battery your fob needs
The easiest way is to open your fob and look at the old battery. The battery itself is stamped with a code—CR2032, CR2025, CR2016, or similar. Write that code down or take a photo with your phone. When you go to the store, show the photo or tell the clerk the code, and they will hand you the right battery.
If you cannot open the fob yet, check your owner's manual. The manual often lists the battery type in the key fob section. You can also search online for "[your car make and year] key fob battery" and find the answer in seconds. Do not guess—buying the wrong size wastes money and time.
Open your fob without breaking it
There are three common ways fobs open, and your model uses one of them. The first is a sliding lever on the side or back of the fob. Push or slide it in the direction the arrow points, and the fob will split in half. The second is a hidden button you press to release a catch—look for a small indent or button on the edge. The third is a seam you pry open with a flat tool like a coin or a plastic pry tool.
Start gently. If you use a coin or screwdriver, wrap it in a thin cloth so you do not scratch the plastic. Work around the seam slowly rather than forcing one spot. The fob is held together by a plastic clip, not glue, so it will come apart if you work the seam evenly. If you are stuck, search "[your fob model] how to open" on YouTube—seeing it done takes the guesswork out.
Remove the old battery and install the new one
Once the fob is open, you will see a small metal holder with the battery sitting in it. The holder has a plus sign (+) stamped on one side. The plus sign tells you which way the battery should face—the plus side of the battery goes up, toward the plus sign on the holder. Gently pry the old battery out with your fingernail or a plastic tool. Do not use a metal screwdriver, which can damage the holder.
Drop the new battery into the holder with the plus side facing up. It should sit flat and snug. If it falls out or sits loose, you may have it upside down—flip it and try again. That is the only way to get it wrong, and it is straightforward to fix.
Close the fob and test it
Snap or slide the fob back together. Make sure both halves line up evenly and click into place. Press a button—lock, unlock, or panic—and listen for the click or feel for the vibration from your car. If it works, you are done. If it does not, open the fob again and flip the battery over. Close it and test again.
If the fob still does not work after flipping the battery, the problem is not the battery. The button contacts inside may be worn or corroded, or water may have damaged the circuit board. In that case, you will need a replacement fob from your car dealer or a locksmith.
Where to buy a replacement battery
Coin-cell batteries are sold everywhere: pharmacies like CVS and Walgreens, grocery stores, hardware stores like Home Depot and Lowe's, and online retailers. You do not need to go to a car dealer or a locksmith. A CR2032 or CR2025 costs between $3 and $10 depending on the brand and where you buy it. Store brands are the same as name brands and cost less.
If you are buying online, make sure the listing says the battery is fresh—some old stock sits in warehouses and loses charge. A battery from a pharmacy or grocery store is almost always fresher because stores restock often.
What to do if your fob has a non-replaceable battery
Some newer fobs, especially those with touchscreens or advanced features, have a sealed battery that cannot be opened by hand. If you cannot find a seam or button after checking your manual and searching online, your fob is sealed. In that case, you will need to take it to your car dealer or a locksmith to have the battery replaced. They charge $15 to $50 for the service, depending on the fob model.
Before you go, call ahead and ask if they can do it the same day. Most can, but some require an appointment. Bring your car keys and proof of ownership so they can confirm the fob belongs to your vehicle.
Frequently Asked Questions
Can I use a different battery size if I cannot find the exact one?
No. A CR2032 and a CR2025 look similar but have different thicknesses, and using the wrong one can prevent the fob from closing properly or cause the battery to lose contact. Spend the extra minute to find the exact size—it is always available somewhere nearby.
What if I put the battery in backwards?
Nothing breaks. The fob straightforward will not work. Open it again, flip the battery so the plus side faces up, and close it. That is the only mistake you can make, and it is completely reversible.
How long does a new battery last?
Most coin-cell batteries last three to four years in a key fob. If you use the fob heavily—pressing buttons many times a day—it may last two to three years. You will notice the buttons becoming less responsive before the battery dies completely.
Should I replace the battery even if the fob still works?
No. Wait until the buttons stop responding or only work when you press hard. Replacing a battery that still has charge wastes money. A fob will usually give you weeks of warning before it stops working entirely.
Can water damage a key fob battery?
Water can damage the circuit board and button contacts, but not the battery itself. If your fob got wet and stopped working, a new battery will not fix it. You will need a replacement fob from your dealer or locksmith.