The most common key fob battery is CR2032, a coin-shaped battery 20 millimeters wide and 3.2 millimeters thick

CR2032 batteries power the majority of car key fobs, garage door remotes, and small electronic devices. The letters and numbers tell you the exact size: CR means lithium coin cell, 20 is the diameter in millimeters, and 32 is the thickness in tenths of a millimeter. You can find CR2032 batteries at any pharmacy, grocery store, hardware store, or online retailer for between $3 and $8 for a pack of two or four.

However, not every key fob uses CR2032. Some older car remotes use CR2025 (slightly thinner), some use CR2016 (noticeably smaller), and a few use AAA or AA batteries instead. The only reliable way to know which battery your fob needs is to open it and look at the battery itself, or check your vehicle's owner manual.

Key Takeaways

  • CR2032 is the standard battery for most car key fobs, and you can buy it at any drugstore or supermarket without special ordering.
  • The battery size is printed directly on the battery itself, so opening your key fob is the fastest way to find out what you need.
  • Coin cell batteries last between three and four years in a typical key fob before the battery drains completely.
  • When you replace the battery, pay attention to which side faces up — the flat side usually goes down, the raised side up — or the fob will not work.

How to find out what battery your key fob needs

Open your key fob by sliding a coin or flat screwdriver into the seam between the two halves. Gently twist until the case pops apart. Do not force it — most fobs are designed to separate easily, and forcing them can crack the plastic.

Once the fob is open, look at the battery sitting in the case. The battery itself is stamped with its size code. Write down the code (it will look like CR2032, CR2025, or similar) and close the fob back up. If you cannot read the code clearly, take a photo of the battery with your phone and bring it to the store with you.

If your key fob does not open easily or you are uncomfortable opening it, check your vehicle's owner manual. The manual lists the battery type for your specific year and model. You can also call your car's dealership parts department — they can tell you the battery size in under a minute.

CR2032 versus other common key fob batteries

CR2032 is the thickest and most common coin cell battery. CR2025 is slightly thinner (2.5 millimeters instead of 3.2) and fits some older remotes. CR2016 is noticeably smaller and thinner, used in some compact key fobs and small devices. CR2430 is thicker and larger than CR2032, used in fewer remotes but common in some medical alert buttons and fitness trackers.

The wrong size battery will not fit in the case, or it will fit but make poor contact with the metal contacts inside the fob. If you buy the wrong size, you will know when ready when you try to install it. Do not force a battery into a fob if it does not slide in smoothly — you risk damaging the contacts or the case.

Some key fobs use AAA or AA batteries instead of coin cells. These are larger and easier to spot. If your fob uses one of these, the battery compartment will be obvious when you open it, and you can buy replacements anywhere batteries are sold.

How to install a new battery in your key fob

Open the fob the same way you did to check the battery — slide a coin into the seam and gently twist. Remove the old battery by prying it up with your fingernail or the edge of a coin. Do not use a sharp metal tool that could scratch the metal contacts inside the fob.

Before you install the new battery, look at the metal contacts inside the fob. They should be clean and shiny. If they look dark or corroded, wipe them gently with a dry cloth or a pencil eraser. Corrosion prevents the battery from making good contact and can cause the fob to stop working even with a new battery.

Slide the new battery into the case with the flat side down and the raised side up. This is the standard orientation for most coin cell batteries. Press down gently until you hear or feel a click — the battery should sit flush with the case. Close the fob by pressing the two halves together until they snap. Test the fob by pressing a button and watching your car or garage door respond.

How long a key fob battery lasts

A CR2032 battery in a typical car key fob lasts between three and four years. This assumes normal use — pressing the button a few times a day. If you use your key fob constantly, the battery may drain faster. If you rarely use it, it may last longer.

Some fobs drain batteries faster than others. Older fobs with worn contacts, fobs that are exposed to extreme heat or cold, and fobs with multiple buttons or LED lights all drain batteries more quickly. If your fob stops working after only a year or two, the battery may be the problem, but it could also be a worn contact or a damaged circuit board.

Where to buy key fob batteries

CR2032 and other common coin cell batteries are sold at pharmacies (CVS, Walgreens), grocery stores, hardware stores (Home Depot, Lowe's), big-box retailers (Target, Walmart), and online (Amazon, eBay). A single battery costs between $1 and $3, and multi-packs of two to four batteries cost between $3 and $8. Prices vary by store and brand.

Generic batteries work just as well as name brands like Energizer or Duracell for key fobs. The battery does not need to be rechargeable — standard single-use lithium coin cells are the right choice. Avoid buying batteries from gas stations or convenience stores, where prices are often double the supermarket price.

What to do if your key fob still does not work after replacing the battery

If you installed a new battery and the fob still does not respond, the problem is likely not the battery. Check that the battery is installed with the correct side facing up — the flat side should be down, the raised side up. Open the fob again and reseat the battery by removing it and pressing it back in firmly.

If the fob still does not work, the metal contacts inside may be corroded or damaged. Open the fob and look at the two small metal circles where the battery touches. If they are dark, dull, or pitted, clean them gently with a pencil eraser or a dry cloth. If they are visibly damaged or broken, the fob may need professional repair or replacement.

If the contacts look clean and the battery is installed correctly, the circuit board inside the fob may be damaged. This is not something you can fix at home. Contact your car's dealership or a locksmith to have the fob repaired or replaced.

Frequently Asked Questions

Can I use a different brand of CR2032 battery in my key fob?

Yes. Generic CR2032 batteries work the same as name brands like Energizer or Duracell. The battery code CR2032 is a standard size, so any battery with that code will fit and function in your fob. Price and availability vary by brand, but performance is essentially identical for key fob use.

What happens if I install the battery upside down?

The fob will not work. Coin cell batteries have a positive side (the raised side) and a negative side (the flat side). If you install it backwards, the electrical connection breaks and the fob will not respond to button presses. straightforward open the fob again and flip the battery over.

How do I know if my key fob battery is dead or if the fob is broken?

Replace the battery first. A dead battery is the most common reason a key fob stops working, and a new battery costs only a few dollars. If the fob works after you install a new battery, the old battery was the problem. If it still does not work, the fob itself may be damaged.

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

Rechargeable coin cells exist, but they are not recommended for key fobs. Rechargeable batteries have a lower voltage than standard lithium coin cells and may not provide enough power to operate your fob reliably. Stick with standard single-use CR2032 batteries.

Is it safe to replace a key fob battery myself?

Yes. Replacing a key fob battery is safe and takes less than two minutes. The battery is not toxic, and the voltage is too low to cause injury. The only risk is damaging the plastic case if you force it open, so open it gently and do not pry too hard at the seam.