Most key fob batteries last between three and four years
A typical car key fob battery lasts somewhere between three and four years under normal use. The exact lifespan depends on how often you press the buttons, which type of battery your fob uses, and whether the fob sits in a pocket where it gets accidentally pressed repeatedly. Some people get five years out of a battery; others need a replacement after two years. The only way to know when yours is dying is to watch for the warning signs.
The battery itself is usually a coin-cell battery — a small, flat, round battery about the size of a dime. The most common types are CR2032, CR2025, and CR2016. These are not rechargeable. When the battery runs down, you replace it, not the fob.
Key Takeaways
- Key fob batteries typically last three to four years with normal use, though this varies based on how often you use the buttons.
- The first sign of a dying battery is usually that you have to press the button harder or multiple times to lock or unlock the car.
- Replacing a key fob battery costs between $5 and $15 for the battery itself, and you can do it yourself in under a minute with no tools.
- If the fob still does not work after you replace the battery, the problem is likely the fob itself, not the battery, and you may need a new fob from the dealer.
Signs your key fob battery is running low
The most common warning sign is that the buttons stop responding the first time you press them. You have to press the unlock button twice, or hold it down longer than you used to. The range also shrinks — you might have to stand closer to the car for the fob to work. These are the clearest signals that the battery is weakening.
Some fobs have a light that flashes when you press a button. If that light becomes dimmer or stops flashing altogether, the battery is nearly dead. If your fob has no light, you will not get that warning — you will just notice the buttons becoming less responsive.
A fob that works sometimes and not other times, or one that only works when you press the button in a certain way, is almost always a battery issue. The battery still has enough charge to work occasionally, but not enough to work reliably.
How to replace a key fob battery yourself
Most key fobs can be opened without any tools. Look for a small slot or seam on the edge of the fob — usually on the side or the back. Slide a fingernail or a coin into the slot and gently twist to pop the fob open. Some fobs have a button you press to release the battery cover instead. The cover usually comes off in two pieces.
Once the fob is open, you will see the battery sitting in a small metal holder. Note which side is facing up — the positive side (marked with a + sign) should face toward you. Lift the battery out gently. Take it to a pharmacy, grocery store, or hardware store and buy a replacement of the same type. The type number is printed on the old battery.
Slide the new battery into the holder with the positive side facing the same direction as the old one. Close the fob by pressing the two pieces together until you hear or feel a click. Test the buttons to make sure they work. If they do not, open the fob again and check that the battery is seated properly and facing the right direction.
What to do if a new battery does not fix the problem
If you installed a fresh battery and the fob still does not work, the problem is not the battery. The issue is usually inside the fob itself — a broken button contact, a cracked circuit board, or water damage. At that point, replacing the battery will not help.
Your options are to buy a replacement fob from the car dealer, buy an aftermarket fob from an online retailer, or have a locksmith program a used fob to your car. Dealer fobs are the most expensive but are may provide to work with your car. Aftermarket fobs are cheaper but vary in quality. A locksmith can sometimes program a used fob for less than a new one costs, though not all locksmiths offer this service.
Before you buy a replacement, try cleaning the battery contacts inside the fob with a dry cloth or a pencil eraser. Corrosion or dirt on the metal contacts can prevent the battery from making a good connection. Wipe the battery itself clean as well. This straightforward step fixes the problem in some cases.
Factors that shorten battery life
If your key fob battery dies much faster than three or four years, something is draining it faster than normal. The most common culprit is a button that is stuck or being pressed repeatedly — for example, if the fob is in a pocket with something pressing against it, or if a child is playing with it. A stuck button will drain the battery in months instead of years.
Water damage also shortens battery life. If the fob has been exposed to rain, spilled on, or dropped in water, moisture inside the fob can corrode the battery contacts or the circuit board. The fob may still work for a while, but the battery will drain faster. If you suspect water damage, let the fob dry completely in a warm, dry place for several days before using it again.
Extreme heat or cold can also affect battery performance, though this is usually temporary. A battery that seems dead in winter may work again once it warms up. If the fob works fine in warm weather but fails in cold weather, the battery is probably just weak and needs replacing soon.
Buying and storing replacement batteries
Key fob batteries are inexpensive and widely available. You can buy them at any pharmacy, grocery store, hardware store, or online retailer. A single battery usually costs between $3 and $8. Buy a few extras and keep them at home so you have one on hand when you need it.
Store batteries in a cool, dry place away from metal objects. Do not store them loose in a drawer where they might touch coins or keys — metal can create a short circuit and drain the battery. A small plastic bag or a battery organizer works well. Batteries stored properly will last for years before you use them.
Check the expiration date on the package before you buy. Most batteries have a shelf life of five to ten years, but older stock may not last as long once installed in your fob.
When to replace the entire fob instead of just the battery
If your fob is old, cracked, or has been dropped multiple times, replacing just the battery may not be worth your time. A fob with a cracked case can let in moisture, which will damage the new battery and the circuit board. If the buttons are worn or sticky, they may fail soon even with a fresh battery.
If your car is more than ten years old, the fob itself may be becoming unreliable. Older fobs have older electronics that wear out over time. At that point, buying a new fob — whether from the dealer or an aftermarket supplier — may be more cost-effective than replacing batteries repeatedly.
Most people find that replacing the battery is the right choice if the fob is less than five years old and has no visible damage. If the fob is older or damaged, a new fob is usually the better investment.
Frequently Asked Questions
Can I use any battery in my key fob?
No. You must use the exact type of battery your fob was designed for. The type number is printed on the old battery. Using the wrong size or type can damage the fob or cause it to malfunction. If you are not sure which battery to buy, take the old battery to the store and match it to a replacement.
Is it bad to leave a dead battery in the fob?
A dead battery will not damage the fob, but it can corrode if left inside for a very long time. If you know the battery is dead and you are not planning to replace it soon, remove it and store it separately. This prevents corrosion from building up inside the fob.
Why does my key fob battery die so fast?
The most common reason is a button that is stuck or being pressed repeatedly. Check that no buttons are sticking and that the fob is not in a pocket where something is pressing against it. If the fob has been wet, water damage inside can also drain the battery quickly. Let it dry completely and replace the battery.
Can I recharge a key fob battery?
No. The batteries used in key fobs are not rechargeable. Once they run down, you must replace them with a new battery of the same type. Do not attempt to recharge a coin-cell battery — it can overheat or leak.
How do I know which battery type my fob uses?
Open the fob and look at the battery. The type number is printed directly on the battery — usually something like CR2032 or CR2025. Write down the number and take it with you when you buy a replacement. If you cannot read the number, take the old battery to the store and match it to a new one.