Most key fobs use a coin-cell battery, usually CR2032 or CR2025

The battery in your key fob is almost certainly a coin-cell battery — a small, flat, round battery about the size of a dime or slightly larger. The most common type is the CR2032, which is 20 millimeters across and 3.2 millimeters thick. Some fobs use the slightly thinner CR2025 (also 20mm across but 2.5mm thick), and a few older or smaller fobs use CR2016 or even CR1632. All of these are lithium batteries that produce 3 volts.

You can find the exact battery type printed on the fob itself — usually on the back or inside the battery compartment. If you cannot find it printed there, the model number of your fob (often on the back as well) will tell you what battery it needs. A quick search for your fob model plus "battery" will show you the right replacement.

Key Takeaways

  • CR2032 is the most common key fob battery, found in the majority of car key fobs made in the last 20 years.
  • The battery type is printed on the fob itself or can be found by searching your fob's model number online.
  • Coin-cell batteries last between three and four years in typical use before the fob stops working reliably.
  • You can replace the battery yourself in most fobs by prying open the case with a coin or flathead screwdriver — no tools or special knowledge required.
  • Coin-cell batteries are inexpensive and sold at pharmacies, grocery stores, hardware stores, and online retailers.

How to identify which battery your fob needs

Open your key fob by inserting a coin or flathead screwdriver into the seam and gently twisting. Most fobs split into two halves. Once open, look at the battery itself — the battery code is stamped or printed directly on the metal surface. Write down that code (it will be letters and numbers like CR2032) and keep it with you when you shop for a replacement.

If the battery is corroded or you cannot read the marking, search online for your car's year, make, and model plus "key fob battery." You can also call your car dealership with your fob's model number, and they will tell you the correct battery. Many auto parts stores will also identify the battery for you if you bring the fob in.

When a coin-cell battery starts to fail

A CR2032 battery typically lasts three to four years in a key fob, though this varies depending on how often you use the fob. Signs that the battery is dying include the fob working only when held close to the car, buttons requiring harder presses to work, or the fob working intermittently. Some fobs will work perfectly one day and fail the next, while others gradually lose range over weeks.

If your fob stops working, a dead battery is the first thing to check. Before you assume the fob itself is broken, replace the battery — it costs a few dollars and takes less than five minutes. If the fob still does not work after a fresh battery, then the internal circuitry may be damaged, and you will need a replacement fob from your dealership or an aftermarket supplier.

Where to buy replacement coin-cell batteries

CR2032 and CR2025 batteries are sold almost everywhere: pharmacies like CVS and Walgreens, grocery stores, hardware stores like Home Depot and Lowe's, big-box retailers like Walmart and Target, and online at Amazon. A single battery costs between 50 cents and two dollars depending on the brand and where you buy it. Buying a multi-pack (usually 4 or 5 batteries) is cheaper per battery if you have multiple fobs or want spares on hand.

Look for the battery in the electronics section, the watch and jewelry section, or near the checkout counter. The packaging will clearly show the battery code (CR2032, CR2025, etc.), so you can verify you have the right one before you buy. Generic and name-brand batteries (Energizer, Duracell, Panasonic) all work equally well in key fobs.

How to replace the battery yourself

Open the fob by inserting a coin or flathead screwdriver into the seam between the two halves and gently twisting. Do not force it — most fobs are designed to open easily. Once the fob is open, note which side of the battery is facing up (the positive side is usually marked with a + symbol). Remove the old battery by gently prying it out with the screwdriver or your fingernail.

Insert the new battery with the positive side facing the same direction as the old one was. Close the fob by pressing the two halves together until they snap. Test the fob by pressing each button and walking toward your car — the doors should lock and unlock normally. If the fob does not work, open it again and check that the battery is inserted correctly and making good contact with the metal contacts inside.

Why CR2032 is the standard for key fobs

The CR2032 became the standard for key fobs because it offers the right balance of size, power, and cost. It is small enough to fit inside a compact fob case, produces enough voltage to power the transmitter circuit reliably, and lasts long enough that owners do not have to replace it constantly. The "CR" prefix means it is a lithium coin cell, the "20" refers to its 20-millimeter diameter, and the "32" refers to its 3.2-millimeter thickness.

Manufacturers could use smaller batteries to make fobs thinner, but the battery would die faster and the fob would be harder to hold and press. They could use larger batteries for longer life, but the fob would be bulkier. The CR2032 hits the practical middle ground, which is why it has remained the industry standard for decades.

Frequently Asked Questions

Can I use a different battery if I do not have the exact type?

No — use only the battery type specified for your fob. Using the wrong battery can damage the fob's circuitry or cause it to malfunction. CR2032 and CR2025 are not interchangeable even though they look similar, because the thickness affects how the battery contacts align inside the fob. Always match the code printed on your old battery or in your fob's manual.

How long does a coin-cell battery last in a key fob?

Most CR2032 batteries last three to four years in typical use. If you use your fob very frequently (pressing buttons dozens of times per day), the battery may last only two to three years. Light use can extend the life to four or five years. The battery will gradually lose power over time, so you may notice the fob working only at close range before it stops working entirely.

What should I do with the old battery?

Lithium coin-cell batteries should not go in the trash — they can be recycled. Many retailers that sell batteries, including Best Buy, Home Depot, and some pharmacies, have battery recycling programs. You can also search for a local recycling center using Earth911.com or your city's waste management website. Some programs accept batteries for free, while others charge a small fee.

Will the fob work if I put the battery in upside down?

No. If the battery is inserted with the negative side facing up instead of the positive side, the fob will not work at all. The metal contacts inside the fob are designed to touch only the positive and negative terminals in the correct orientation. If your new fob does not work, open it and check that the + symbol on the battery is facing the same direction as it was on the old battery.

Can I use a rechargeable coin-cell battery in my key fob?

Rechargeable coin-cell batteries exist, but they are not recommended for key fobs. Rechargeable batteries produce slightly lower voltage (usually 1.5 volts instead of 3 volts) and may not power the fob reliably. They also lose charge over time even when not in use, so your fob could stop working unexpectedly. Stick with standard lithium coin-cell batteries like CR2032 for consistent performance.