Most key fobs use a coin-cell battery, usually CR2032, CR2025, or CR2016

The battery inside your key fob is almost certainly a coin-cell battery — a small, flat, round battery about the size of a dime. The most common type is the CR2032, which works in the majority of car key fobs, garage door openers, and remote controls. Other common sizes are the CR2025 (slightly thinner) and CR2016 (even thinner). All three are 3-volt lithium batteries and cost between $3 and $8 for a pack of two or four at any drugstore, supermarket, or hardware store.

The exact battery your fob needs is printed on the old battery itself once you open the fob. If you have not opened it yet, you can also check your vehicle's owner's manual — most include a diagram showing which battery type goes in your specific fob. Some manufacturers print the battery type on the back of the fob itself, usually in small text near the model number. If you cannot find it anywhere, a staff member at any drugstore can match your old battery in seconds.

Key Takeaways

  • CR2032 is the standard battery for most car key fobs, but CR2025 and CR2016 are also common — check your old battery or owner's manual to be sure.
  • Coin-cell batteries cost $3 to $8 per pack and are sold at drugstores, supermarkets, and hardware stores without any special ordering.
  • Opening a key fob usually requires only a flathead screwdriver or a coin to pry the two halves apart — no tools or special knowledge needed.
  • When you install the new battery, the positive side (marked with a +) should face up toward the button, and the negative side should face the circuit board.

How to open your key fob and replace the battery

Most key fobs split into two halves along a seam that runs around the edge. Look for a small slot or groove on the side of the fob — this is where you insert a flathead screwdriver or a coin (a penny or dime works well). Gently twist or pry until the two halves separate. Do this over a table or towel so you do not lose the small spring or gasket that may fall out.

Once the fob is open, you will see the coin-cell battery sitting in a small metal holder. Note which side is facing up — the positive side, marked with a + symbol, should be facing toward the button side of the fob. Gently pry the old battery out with your fingernail or the edge of a coin, then drop the new battery in with the positive side facing the same direction. Press down gently until it clicks into place in the metal holder.

Close the fob by pressing the two halves together until they snap. You may hear a click. Test the fob by pressing each button — the light should come on and the car should respond. If nothing happens, open the fob again and check that the battery is seated correctly and facing the right direction.

Where to buy coin-cell batteries

Coin-cell batteries are sold everywhere: drugstores (CVS, Walgreens), supermarkets (Walmart, Target, Kroger), hardware stores (Home Depot, Lowe's), and online (Amazon). You do not need to order them or wait for delivery. A pack of two or four CR2032 batteries costs $3 to $8 depending on the brand and where you shop. Store brands are the same quality as name brands like Energizer or Duracell and cost less.

If you are not sure which battery you need, bring your old fob or the old battery with you to the store. A staff member can match it for you in seconds. You can also call ahead — most stores keep these batteries in stock year-round in the battery aisle or near the checkout counter.

Signs your key fob battery is dying

A dying battery usually shows itself gradually. The fob may work only when you hold it very close to the car, or you may have to press the button several times before the car responds. The light inside the fob (if it has one) may dim or stop working altogether. In cold weather, a weak battery may fail completely, then work again when it warms up.

If your fob stops working suddenly and completely, the battery is likely dead. However, if the fob has been dropped or exposed to water, the problem may be inside the circuit board rather than the battery. In that case, replacing the battery will not help, and you will need a new fob from your car manufacturer or a locksmith.

How long a key fob battery lasts

A coin-cell battery in a key fob typically lasts three to four years, depending on how often you use the fob. If you press the button dozens of times a day, the battery will wear out faster. If you use the fob only occasionally, it may last longer. Batteries also lose power over time even when not in use — a battery sitting in a drawer will slowly discharge.

The battery will not suddenly die at the three-year mark. Instead, you will notice it working less reliably over weeks or months. Once you replace it, the new battery should work reliably for another three to four years.

What to do with the old battery

Coin-cell batteries contain lithium and should not go in the trash. Most drugstores and supermarkets have a battery recycling bin near the customer service desk or in the pharmacy section — you can drop off old batteries for free. Some hardware stores also accept batteries. If you cannot find a drop-off location nearby, Earth911.com has a searchable database of recycling centers in your area that accept batteries.

Recycling takes only a minute and keeps lithium out of landfills. Many people keep a small bag of old batteries in a drawer until they have a few to drop off together, which is a practical way to handle them.

When to call a professional instead

If you open the fob and the battery compartment is corroded (green or white crusty buildup), the fob may be damaged beyond a straightforward battery replacement. Corrosion usually means water got inside. In that case, a new battery will not help, and you will need a replacement fob. Contact your car manufacturer's dealership or a local locksmith for a new fob — they can order one and program it to your car.

If the fob has been dropped or sat in water, do not try to force it open. The circuit board inside may be damaged, and forcing it could break it further. A locksmith or dealership can assess whether the fob is repairable or needs replacement. Most dealerships charge $200 to $400 for a new fob with programming, though prices vary by manufacturer.

Frequently Asked Questions

Can I use a different battery size if I cannot find the exact one?

No. CR2032, CR2025, and CR2016 are not interchangeable — they have different thicknesses and may not fit properly in the battery holder. Using the wrong size can damage the fob or cause poor contact. Always use the exact battery type printed on your old battery or listed in your owner's manual.

Does it matter which side of the battery faces up?

Yes, it matters. The positive side (marked with a +) must face toward the button side of the fob. The negative side faces the circuit board. If you install it backward, the fob will not work. When you open the fob, note which way the old battery was facing, then install the new one the same way.

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

First, open the fob again and check that the battery is seated firmly in the metal holder and facing the correct direction. If it is, the problem is likely inside the circuit board — water damage, a broken button, or a loose wire. You will need a replacement fob from your dealership or a locksmith.

Can I buy a bulk pack of batteries and store them?

Yes. Coin-cell batteries last for years in storage if kept in a cool, dry place. Buying a bulk pack is cheaper per battery than buying single packs. Just keep them in their original packaging or in a sealed container to prevent them from touching other metal objects, which can cause them to discharge.