Car fob batteries are cheap and straightforward to swap yourself

Most car fobs use a coin-cell battery that costs between $3 and $8 and takes about two minutes to replace. You do not need tools or a mechanic — just the fob itself and a new battery of the correct size. The hardest part is usually figuring out which battery your fob needs, but the model number printed on the fob case tells you exactly what to buy.

If your fob is not responding, a dead battery is the most common reason. Before you replace it, press the buttons a few times while holding the fob close to your car — sometimes a weak battery will work from a short distance. If nothing happens, or if the buttons work only occasionally, the battery is likely dead and ready to be replaced.

Key Takeaways

  • Car fob batteries are coin-cell batteries (usually CR2032, CR2025, or CR2016) that you can buy at any pharmacy, grocery store, or hardware store for under $10.
  • The battery model number is printed on the fob case itself, so you know exactly which one to buy before you leave home.
  • Opening the fob requires only a flat tool like a coin or flathead screwdriver — no special equipment needed.
  • Replacing the battery takes about two minutes and involves sliding the old battery out and sliding the new one in, paying attention to which side faces up.

Find the battery model number on your fob

Look at the edge or back of your fob case. You will see a small model number printed there, usually starting with "CR" followed by four digits. The most common models are CR2032, CR2025, and CR2016. Write down this number or take a photo with your phone.

If you cannot find a printed number, check your car's owner manual — it often lists the fob battery type. If that does not work, you can also ask the parts counter at any auto parts store or pharmacy to look it up by your car's year, make, and model.

Buy the correct replacement battery

Take the model number to any pharmacy, grocery store, hardware store, or auto parts store. Coin-cell batteries are stocked in the watch and battery section, usually near the checkout or in the health and beauty area. A single battery costs $3 to $8 depending on the brand and store.

You can also order online from Amazon, eBay, or the store's website if you prefer. Many people buy a two-pack or four-pack since the batteries last several years and you may need another one later. Check the expiration date on the package — batteries do not go bad, but old stock is sometimes discounted.

Open the fob case

Look for a seam running around the edge of the fob. Most fobs split into two halves along this seam. Insert a flat tool — a coin, flathead screwdriver, or even a butter knife — into the seam and gently twist or pry. The case will pop open, usually with a small click.

Some fobs have a small slot or notch on one edge instead of a full seam. If you see a slot, insert your flat tool there and twist gently. Do not force it — if the fob does not open easily, you may be prying in the wrong spot. Rotate the fob and try a different edge of the seam.

Once the case opens, you will see the battery sitting in a small metal holder or clip. The battery is round and flat, about the size of a dime. Do not lose the small rubber or plastic gasket that may fall out — you will need it when you close the fob again.

Remove the old battery and insert the new one

Slide the old battery out of its holder. If it is stuck, use your fingernail or the edge of your flat tool to gently pry it up. Do not bend or scratch the metal holder — it needs to grip the new battery firmly.

Before you insert the new battery, look at which side is facing up on the holder. Most batteries have a flat side (negative) and a slightly raised side (positive). The positive side should face up toward you. Slide the new battery into the holder with the correct side facing up, and it should click into place.

If the battery does not click or feels loose, remove it and flip it over — you may have inserted it upside down. The battery should sit snugly in the holder and not rattle when you shake the fob gently.

Close the fob and test the buttons

Line up the two halves of the fob case and press them together firmly. You should hear or feel a small click as the case snaps shut. If the case does not close evenly or feels loose, open it again and make sure the battery is sitting flat in its holder and the gasket is in place.

Once the case is closed, press each button on the fob several times while standing near your car. You should see the car's lights flash or hear the locks click. If nothing happens, open the fob again and check that the battery is inserted with the correct side facing up. If the battery is correct and the fob still does not work, the problem may be something other than the battery — a broken button or circuit board — and you may need a replacement fob from your car dealer.

When to replace the fob instead of just the battery

If you replace the battery and the fob still does not work, the problem is likely inside the fob itself. Water damage, a cracked circuit board, or worn-out buttons can all prevent a fob from working even with a fresh battery. In these cases, you will need to buy a replacement fob from your car dealer or a third-party seller.

Replacement fobs range from $50 to $400 depending on your car's make and model. Some dealers will program a fob you buy elsewhere, while others require you to buy from them. Call your dealer's parts department to ask about your options and pricing before you buy.

Frequently Asked Questions

How long does a car fob battery last?

Most fob batteries last three to four years with normal use. If you use your fob frequently — pressing the buttons multiple times a day — the battery may last only two to three years. Some people replace the battery once a year as preventive maintenance.

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

No. Using the wrong size battery can damage the fob's circuit board or cause the battery to not make proper contact. Always use the exact model number printed on your fob. If you cannot find that model, ask the store to order it or check a different store.

What do I do with the old battery?

Coin-cell batteries can be recycled at most pharmacies, grocery stores, and auto parts stores — just ask at the customer service desk. Some stores have a battery recycling bin near the checkout. Do not throw batteries in the trash.

Do I need to reprogram my fob after replacing the battery?

No. Replacing the battery does not erase the fob's programming. Once you insert the new battery and close the case, the fob should work when ready without any reprogramming steps.

What if my fob has two batteries instead of one?

Some older or larger fobs use two coin-cell batteries stacked together. If you open your fob and see two batteries, remove both and replace them both with new batteries of the same model. Make sure both batteries are inserted with the correct side facing up.