Most car key fob batteries take two minutes to swap out with tools you already have
A dead key fob battery is one of the easiest car problems to fix yourself. You do not need a mechanic, a special tool, or any technical knowledge. Most fobs use a coin-cell battery (usually CR2032, CR2025, or similar) that costs $3 to $8 and slides out of a plastic case you can open with a coin or a flathead screwdriver. The whole job takes about five minutes.
The hardest part is usually figuring out how your specific fob opens—some slide, some pop, some have a hidden screw. Once you know that, the rest is straightforward: pop the case, note which side of the battery faces up, drop in the new one the same way, and snap it closed.
Key Takeaways
- Most key fob batteries are coin-cell types (CR2032 is the most common) that cost a few dollars and are sold at any pharmacy, grocery store, or hardware store.
- Before you buy a battery, check your owner's manual or the inside of your fob case to see which exact model your fob uses.
- The fob case opens by sliding, popping, or unscrewing—check for a seam, a small slot, or a hidden screw before forcing anything.
- When you install the new battery, pay attention to which side faces up (usually the flat side faces toward the back of the fob) so it makes contact.
- If the fob still does not work after a new battery, the problem is likely a corroded contact or a broken circuit board, not the battery itself.
Find out what battery your fob needs before you buy
The easiest way is to open your fob and look at the old battery itself. The model number is printed right on it—CR2032, CR2025, CR2016, and similar. Write that number down or take a photo, then buy the exact same model at a pharmacy, supermarket, or hardware store. Most stores stock the common types in the watch or battery aisle.
If your fob is already completely dead and you cannot open it, check your owner's manual. The manual usually lists the battery type in the key fob section or in a specifications table. You can also search online for "[your car make and year] key fob battery" and find the answer in seconds.
Do not guess. Putting in the wrong size battery can damage the fob or cause it to work poorly. The few dollars you save by buying the wrong type is not worth it.
How to open your key fob case
Key fobs open in three main ways, and you can usually tell which one yours uses by looking at it closely.
Sliding case: Look for a seam running around the edge of the fob. If you see one, try sliding a coin or your fingernail into the seam and gently prying the two halves apart. Start at the seam, not at a corner—corners are usually glued tighter. Slide slowly and work your way around the edge. The two halves should separate cleanly.
Pop-open case: Some fobs have a small slot or notch on one edge. Insert a flathead screwdriver or a coin into the slot and gently twist or pry. The back half should pop off. If nothing happens after gentle pressure, try a different edge—the slot might be on the side you cannot see from the front.
Screw-open case: Flip the fob over and look for a small screw, usually hidden under a rubber pad or in a corner. Peel back any rubber if you see one, then use a small Phillips or flathead screwdriver (whichever matches the screw head) to remove it. Once the screw is out, the case should open by sliding or popping.
If you cannot figure out how yours opens after a careful look, search "[your car make] key fob how to open" online—you will find photos or videos of your exact model.
Remove the old battery and install the new one
Once the case is open, you will see the battery sitting in a small plastic holder. It is usually held in place loosely, so you can slide it out with your fingernail or a plastic tool. Do not use a metal screwdriver directly on the battery—you can scratch it or cause a short.
Before you throw the old battery away, look at which side is facing up. The side facing the back of the fob (usually the flat side) is the side that makes contact with the metal spring. This matters. Insert the new battery the exact same way—flat side toward the back, rounded side toward the front. If you put it in backwards, the fob will not work.
Once the new battery is in place, close the case. If it slides, slide it firmly until you hear or feel a click. If it pops, press down on the edges until both halves are flush. If there was a screw, replace it and tighten gently—do not over-tighten or you can crack the plastic.
Test the fob and troubleshoot if it still does not work
Press a button on the fob. If the car locks or unlocks, you are done. If nothing happens, try these steps in order.
First, open the fob again and make sure the battery is facing the right direction. A backwards battery is the most common reason a new fob does not work. Flip it and test again.
Second, check the metal contacts inside the fob case. If they look dark, corroded, or dirty, clean them gently with a pencil eraser or a cotton swab dampened with rubbing alcohol. Let them dry completely before closing the fob again. Corrosion on the contacts can block the electrical connection even with a fresh battery.
Third, if the fob still does not work, the problem is likely a broken circuit board or a failed button, not the battery. This is not something you can fix at home. Take the fob to a car dealership or a locksmith—they can repair or replace it. The cost is usually $150 to $300 depending on your car.
Where to buy a replacement battery
Coin-cell batteries are sold almost everywhere: pharmacies (CVS, Walgreens), grocery stores, hardware stores (Home Depot, Lowe's), and online (Amazon). A single battery costs $3 to $8 depending on the brand and where you buy it. Name brands like Duracell and Energizer work fine, but store brands are usually identical and cheaper.
If you want to stock up, buy a pack of two or four. Key fob batteries last two to four years depending on how often you use the fob, so having a spare on hand means you will not have to run out when the battery dies.
Frequently Asked Questions
Can I use a rechargeable battery in my key fob?
No. Rechargeable coin-cell batteries (like rechargeable CR2032s) have a lower voltage than disposable ones and will not work reliably in a key fob. Stick with a standard disposable battery of the correct type.
What if I cannot get the fob case open without breaking it?
Stop and do not force it. A locksmith or car dealership can open it without damage and replace the battery for you—usually $15 to $30 in labor. It is cheaper than buying a new fob if you crack the case.
How long does a key fob battery last?
Most coin-cell batteries last two to four years in a key fob, depending on how often you press the buttons. Heavy use drains them faster. If your fob dies much sooner, the fob itself may have a problem draining power.
Is it safe to handle a coin-cell battery with my bare hands?
Yes. Coin-cell batteries are safe to touch. Wash your hands afterward if you prefer, but there is no danger from handling them briefly. Do not swallow one or put it in your mouth.
What should I do with the old battery?
Most coin-cell batteries can go in the regular trash, but some areas have battery recycling programs. Check your local rules. If you want to recycle, most pharmacies and electronics stores have battery drop-off bins near the front.