Finding the Right Battery for Your Key Fob

The battery your key fob needs depends on the specific model of your car and fob — there is no single answer that works for all fobs. Most car key fobs use a coin-cell battery, which is a small, flat, round battery about the size of a dime or quarter. The most common types are CR2032, CR2025, and CR2016, where the numbers tell you the size and voltage. A CR2032 is 20 millimeters in diameter and 3.2 millimeters thick; a CR2025 is the same diameter but slightly thinner at 2.5 millimeters; a CR2016 is thinner still at 1.6 millimeters.

The easiest way to find out which battery your fob needs is to open it and look at the battery itself — the type is printed right on it. If your fob is already dead and you cannot open it, check your car's owner's manual, which lists the battery type in the key fob section. You can also call your car dealership with your vehicle's year, make, and model, and they will tell you when ready. Many auto parts stores and pharmacies also have staff who can identify the battery type if you bring the fob in.

Key Takeaways

  • Most car key fobs use a CR2032, CR2025, or CR2016 coin-cell battery, and the type is printed on the battery itself.
  • Your car's owner's manual lists the correct battery type in the key fob section, or you can call your dealership with your vehicle information.
  • Coin-cell batteries cost between two and five dollars at drugstores, supermarkets, and auto parts stores.
  • When you replace the battery, note which side faces outward before you remove the old one, because the new battery must go in the same way.

How to Open Your Key Fob Safely

Most key fobs have a small slot or seam running around the edge where the two halves of the plastic case meet. Look for a flat edge or a small notch on one side — this is where you insert a flat tool to pry the fob open. A flathead screwdriver, a coin, or a plastic spoon works well; avoid using a sharp knife, which can slip and cut your hand.

Insert your tool gently into the seam and twist slightly to create a gap between the two halves. Once you have a small opening, you can usually work your fingers into the gap and pull the halves apart by hand. Some fobs have a small screw holding them together instead of a snap fit — if you see a screw, use a screwdriver that matches its size exactly, because using the wrong size can strip the screw head and make it impossible to open later.

Removing and Replacing the Battery

Before you touch the old battery, look at which side is facing up — the positive side is usually marked with a plus sign and faces outward toward you. The negative side faces the circuit board inside the fob. This matters because putting the battery in backwards will prevent the fob from working, and you will have to open it again to flip it.

Use your fingernail or a plastic tool to gently pry the old battery out of its holder. Do not use a metal tool, which can damage the metal contacts inside the fob. Once the old battery is out, insert the new one with the positive side facing the same direction as the old one was facing. Press down gently until you hear or feel a small click, which means the battery is seated in its holder.

Close the fob by pressing the two halves together until they snap. You should hear a distinct click. Test the fob by pressing each button — if it does not work, open it again and check that the battery is facing the right direction and is fully seated in the holder.

Where to Buy Key Fob Batteries

Coin-cell batteries are sold almost everywhere: drugstores like CVS and Walgreens, supermarkets, Walmart, Target, and auto parts stores like AutoZone and O'Reilly. They are also available online through Amazon and other retailers. Prices vary slightly by location and brand, but a single CR2032 typically costs between two and five dollars. Buying a pack of two or four is usually cheaper per battery than buying a single one.

If you are unsure which battery to buy, bring your fob with you to the store and ask a staff member to identify it. Most stores will open the fob for you right there and tell you the type. This takes two minutes and saves you from buying the wrong battery and having to return it.

Common Battery Types and Their Uses

The CR2032 is by far the most common battery in car key fobs. It is also used in watches, calculators, hearing aids, and small electronic devices. The CR2025 is slightly thinner and is less common in car fobs but still appears in some models. The CR2016 is the thinnest and rarest of the three in automotive fobs, but some manufacturers use it to keep the fob as slim as possible.

A few older or luxury car fobs use different batteries entirely — some use AAA or AA batteries, and a small number use proprietary batteries that only the dealership sells. If your fob does not use a standard coin cell, your owner's manual will specify what it needs. In that case, ordering from the dealership is usually your only option, though some online retailers carry less common fob batteries.

How Long a Key Fob Battery Lasts

A new coin-cell battery in a key fob typically lasts between three and four years under normal use. This assumes you press the buttons a few times a day, which is the typical pattern for most drivers. If you use your fob very frequently — pressing the buttons dozens of times daily — the battery may wear out in two to three years. If you use it rarely, it might last four to five years.

You will notice the fob starting to fail before the battery is completely dead. The buttons may require harder presses, or the fob may work only from a shorter distance. When this happens, it is time to replace the battery. Do not wait until the fob stops working entirely, because a completely dead battery can sometimes leak inside the fob and damage the circuit board.

Frequently Asked Questions

Can I use a regular alkaline battery instead of a coin-cell battery?

No. Alkaline batteries like AA or AAA are too large and have a different voltage than coin cells. Using the wrong battery type will not work and may damage the fob's circuit board. Always use the exact battery type specified for your fob.

What do I do if the fob still does not work after I replace the battery?

First, open the fob again and check that the battery is facing the correct direction — the positive side should face outward. If it is correct and the fob still does not work, the circuit board may be damaged, or the battery contacts may be corroded. Try cleaning the metal contacts inside the fob with a dry cloth or a pencil eraser, then insert a fresh battery and test again.

Is it safe to replace the battery myself, or should I go to the dealership?

Replacing the battery yourself is safe and takes about two minutes. You do not need any special tools beyond a flathead screwdriver or coin. The dealership will do it for you, but they usually charge between ten and thirty dollars for the service, whereas a battery costs two to five dollars.

Can I buy a generic coin-cell battery, or do I need the brand name?

A generic coin-cell battery works just as well as a name-brand one like Energizer or Duracell, as long as it is the correct type — CR2032, CR2025, or CR2016. Generic batteries are usually cheaper and perform identically. Some people prefer name brands for peace of mind, but either will work.

What should I do with the old battery?

Coin-cell batteries contain small amounts of lithium and other materials that should not go in the trash. Many drugstores and supermarkets have battery recycling bins near the checkout or customer service desk. You can also take old batteries to a local recycling center. Some auto parts stores accept them as well.