Most car key 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. You do not need tools, a mechanic, or special knowledge — just the right battery type and two minutes of your time. The whole job involves opening the fob, removing the old battery, and sliding in a new one.
The hardest part is finding out which battery your key uses. Car manufacturers do not standardize fob batteries, so a Honda key takes a different battery than a Toyota key, even if the fobs look similar. Once you know the type, you can buy a replacement at any pharmacy, grocery store, or hardware store for less than the cost of a coffee.
Key Takeaways
- Most car key fobs use a coin-cell battery, usually CR2032, CR2025, or CR2016, printed on the battery itself or visible inside the fob.
- Open the fob by sliding a flat tool into the seam or pressing a release button on the back — the method depends on your fob design.
- Note which side of the battery faces up before you remove it, then insert the new battery the same way.
- If the key still does not work after replacing the battery, the problem is likely a worn contact or a broken circuit board, not the battery itself.
- Dealerships charge $50 to $150 to replace a key fob battery; doing it yourself costs $3 to $10.
Find out what battery your key fob uses
The easiest way is to look at the battery itself. Open your fob and look at the round, flat battery inside — the type is printed on it. Common types are CR2032, CR2025, and CR2016. Write down the number or take a photo with your phone.
If you cannot open the fob yet, check your car's owner manual. The manual lists the battery type for your key fob. You can also search online for your car's year, make, and model plus "key fob battery" — most results will tell you the type within the first sentence.
If you have lost the manual and cannot find the information online, take the fob to any pharmacy or supermarket with a battery section. Staff can usually identify the battery type by looking at the fob, and they will have the replacement in stock.
Open the key fob without breaking it
Car key fobs open in two main ways: a sliding seam or a release button. Look at your fob carefully. If you see a thin line running around the edge, that is the seam — slide a flat tool like a coin or a plastic spoon into it and twist gently to pop the two halves apart. Do not force it; if it does not move, you are using the wrong seam.
If there is no visible seam, look for a small button or slot on the back. Press or slide it, and the fob should split open. Some fobs have a button you press to release the battery holder itself, which then slides out of the plastic case.
Once the fob is open, you will see the battery sitting in a metal holder. Note which side faces up — the positive side (marked with a plus sign) usually faces up, but check before you remove it. Take a photo if you are unsure.
Remove the old battery and install the new one
Gently pry the old battery out of its metal holder using a fingernail or a plastic tool. Do not use a metal screwdriver or anything sharp, because you can damage the holder or the circuit board underneath.
Once the old battery is out, slide the new battery into the holder with the same side facing up as the old one. It should sit flat and click into place. Do not force it — if it does not fit, you have the wrong battery type.
Close the fob by pressing the two halves together until they snap. You should hear or feel a click. Test the key by pressing a button — the car should respond within a few feet. If it does not work, open the fob again and check that the battery is seated properly and facing the right direction.
What to do if the key still does not work
If a new battery does not fix the problem, the issue is not the battery. The metal contacts inside the fob may be corroded or worn, or the circuit board may be damaged. These problems cannot be fixed at home.
Your options are to buy a replacement key fob (usually $50 to $150 from a dealership, or $20 to $60 from an aftermarket seller online) or to have a locksmith reprogram an existing fob. A locksmith typically charges $50 to $100 for reprogramming. If your car is under warranty, the dealership may replace the fob for free.
Before you buy a replacement, test the key one more time in different locations — sometimes a weak signal is caused by interference from power lines or buildings, not a broken fob. If the key works at home but not at the store, the fob is probably fine.
Where to buy replacement batteries
Coin-cell batteries are sold almost everywhere: pharmacies like CVS and Walgreens, supermarkets, hardware stores like Home Depot and Lowe's, and online retailers like Amazon. A single battery costs $3 to $10 depending on the brand and where you buy it. Name brands like Energizer and Duracell are more expensive than store brands, but they last just as long for key fob use.
Buy the battery the same day you plan to replace it, or keep a spare in your car. Batteries have a shelf life of five to ten years, so storing extras is safe. If you buy online, factor in shipping time — most orders arrive in two to three days, but if your key is dead now, a pharmacy is faster.
How long a new battery will last
A new key fob battery typically lasts three to four years with normal use. Heavy users — people who press the fob button dozens of times a day — may need to replace it sooner, sometimes in two years. Light users may get five years or more.
You will know the battery is dying when the key only works from very close to the car, or when you have to press the button multiple times for it to respond. At that point, replace it. Do not wait until the key stops working entirely, because you may be locked out of your car.
Frequently Asked Questions
Can I replace a key fob battery if I do not know what type it is?
Yes. Take the fob to a pharmacy or supermarket with a battery section, and staff can identify the type by looking at it. You can also search online for your car's year, make, and model plus "key fob battery type" — most results show the answer in the first sentence. If you have the owner manual, it lists the battery type.
What if I put the battery in backwards?
The key will not work, but the battery will not be damaged. Open the fob again and flip the battery so the positive side (marked with a plus sign) faces up. This is the correct direction for almost all car key fobs. Close the fob and test it.
Is it safe to replace the battery myself, or should I go to a dealership?
It is completely safe to do it yourself. You are only removing and replacing a battery — there is no risk of damaging the car or the key. Dealerships charge $50 to $150 for the same job, so replacing it yourself saves money and time.
Do all car key fobs use the same battery?
No. Different car brands use different battery types. A Honda key fob might use a CR2032, while a Toyota uses a CR2025. The battery type is printed on the battery itself, so once you open the fob, you will know exactly what to buy.
What should I do with the old battery?
Most coin-cell batteries can be thrown in the trash, but some areas require battery recycling. Check your local rules. Many pharmacies and retailers accept used batteries for recycling at no cost — ask at the customer service desk when you buy the new battery.