Most key fob batteries swap out in under five minutes with no tools
A dead key fob battery is one of the easiest car problems to fix yourself. The battery sits in a small compartment inside the fob, and you can reach it by prying the case open with a coin or your fingernail—no screwdriver needed. The whole job takes about five minutes, costs between $3 and $15 for a replacement battery, and requires no special knowledge.
The hardest part is knowing which battery type your fob uses. Most common fobs use either a CR2032 or CR2025 battery, but some use CR2016 or other sizes. Your owner's manual will tell you which one, or you can check the battery compartment itself—the old battery will have the size printed on it.
Key Takeaways
- Open your key fob by inserting a coin into the seam and twisting gently, or use your fingernail if the case has a notch.
- Note which direction the battery sits (flat side up or down) before you remove it, so you can install the new one the same way.
- Buy the correct battery type—CR2032 is most common, but check your old battery or owner's manual to be sure.
- If the fob still does not work after changing the battery, the problem is likely a worn contact or broken circuit board, not the battery itself.
Find out what battery type your fob needs
The easiest way is to look at the battery already in your fob. Once you open the case, the old battery will have its size stamped on the flat side—usually CR2032, CR2025, or CR2016. Write down the number before you throw the old battery away.
If you cannot open the fob yet or the battery is too corroded to read, check your owner's manual. Search the index for "key fob" or "remote battery." Most manuals list the battery type in a table or in the maintenance section. You can also call your car's dealership with your vehicle identification number (VIN), and they will tell you over the phone.
Do not guess. Putting in the wrong size battery may not fit, or it may fit but not make good contact with the terminals inside. Spend 30 seconds confirming the right type before you buy.
Open the key fob case
Look for a seam running around the edge of your fob—usually horizontal, sometimes vertical. This is where the two halves of the plastic case meet. Insert a coin (a dime or penny works) into the seam and twist gently. You are not trying to pry hard; you are just creating enough pressure to separate the two halves.
If your fob has a small notch or slot on one edge instead of a full seam, use your fingernail or a plastic spoon handle. Avoid metal screwdrivers, which can scratch the case or slip and damage the circuit board inside. Twist slowly and let the plastic do the work—if it is not budging after a few seconds of gentle pressure, you may be twisting in the wrong direction or at the wrong spot.
Once the case cracks open, you should be able to pull the two halves apart by hand. Set the screws or small springs aside if any fall out—they belong back in the same spots when you reassemble.
Remove the old battery and note its position
Before you touch the battery, look at how it sits in the compartment. Is the flat side facing up or down? Is it sitting in a plastic holder or loose in a metal cradle? Take a mental picture or a quick photo with your phone. You will install the new battery the same way.
Gently lift or pry out the old battery. If it is stuck, a plastic spoon handle or the edge of a coin works better than your fingernail—you want to avoid bending the metal contacts inside the compartment. Once the battery is out, set it aside. Do not throw it away yet if you are not 100% sure of the replacement type.
While the compartment is open, look for corrosion—a white, blue, or green crusty buildup on the metal contacts. If you see it, wipe the contacts gently with a dry cloth or a pencil eraser. Corrosion blocks the electrical connection and can prevent a new battery from working even if the battery itself is good.
Insert the new battery and close the fob
Slide the new battery into the compartment in the same position as the old one—flat side up if that is how it was sitting, flat side down if it was upside down. Press gently until you hear or feel a small click. The battery should sit flat and snug, not loose or tilted.
Close the two halves of the case by pressing them together firmly until they snap. You should hear a click or feel resistance when they are fully seated. If the case does not close all the way, the battery may be in backwards or the case halves may not be aligned—open it again and check.
Test the fob by pressing each button a few times. The buttons should feel the same as before—if they feel mushy or stuck, the case may not be fully closed. If the fob still does not work after a minute or two, the battery may be defective, or the problem may be something else inside the fob.
What to do if the new battery does not work
If you installed a fresh battery and the fob still does not respond, the problem is usually not the battery. The most common culprits are worn metal contacts inside the fob, a cracked circuit board, or water damage. These problems require replacing the entire fob, not just the battery.
Before you buy a new fob, try this: open the case again and look at the metal contacts—the small raised bumps or strips where the battery touches the circuit board. If they look black, pitted, or worn smooth, rub them gently with a pencil eraser or fine sandpaper. Reassemble and test. Sometimes this restores the connection enough to make the fob work again.
If that does not work, contact your car's dealership or a locksmith. They can program a new fob to your car, which usually costs $50 to $150 depending on the vehicle. Some newer cars allow you to program a fob yourself using a sequence of key turns and button presses—check your owner's manual under "programming" or "remote control."
Frequently Asked Questions
Can I use a regular alkaline battery instead of a coin cell battery?
No. Alkaline batteries (AA, AAA, 9V) are too large to fit in a key fob compartment. Coin cell batteries like CR2032 are the only type designed for this space. Using the wrong battery can damage the fob or create a fire hazard.
How long does a key fob battery usually last?
Most coin cell batteries last three to four years in a key fob, depending on how often you use the buttons. Heavy use drains the battery faster. If your fob stops working after less than a year, the battery may be defective, or the fob may have a deeper problem.
What if I lose a small spring or screw when I open the fob?
Look carefully inside the case and around your work area—springs and screws are straightforward to miss. If you cannot find it, take the fob to a dealership or locksmith. They have replacement springs and screws on hand and can reassemble it correctly. Reassembling without all the parts can prevent the fob from working.
Is it safe to throw away the old battery in the trash?
Coin cell batteries contain lithium and should not go in regular household trash. Many pharmacies, electronics stores, and auto parts stores have battery recycling bins near the checkout. Some communities also have hazardous waste collection days. Check your local waste management website for drop-off locations.
Can I change the battery while the fob is wet?
No. If your fob got wet, let it dry completely for at least 24 hours before opening it. Opening a wet fob can trap moisture inside and damage the circuit board. Place it in a warm, dry spot or in a container with uncooked rice, which absorbs moisture.