Check Your Key Fob's Battery Compartment First

The fastest way to find out what battery your key fob needs is to open it and look at the old battery itself. Most key fobs have a small slot or button on the side or back that lets you pop the case open without tools. Once it's open, you'll see a coin-shaped battery sitting in a metal holder — that battery will have a number stamped on it, usually something like CR2032, CR2025, or LR44.

Write down that number exactly as it appears. That's your battery type, and it's the only information you need to buy a replacement. If the battery is corroded or stuck, you may need to gently pry it out with a plastic tool or the edge of a coin, but don't force it — you can damage the contact points inside.

If you can't open the fob or the battery marking is worn away, your owner's manual or the car's manual will list the battery type. You can also search online for your specific car make, model, and year plus "key fob battery" — most manufacturers publish this information.

Key Takeaways

  • Open your key fob and read the number stamped on the old battery — that number is the only specification you need to buy the right replacement.
  • CR2032 is the most common key fob battery, but CR2025, CR2016, and LR44 are also widely used depending on your vehicle.
  • Coin-cell batteries (CR and BR types) cost between $3 and $8 for a single battery at drugstores, supermarkets, and online retailers.
  • When you install the new battery, make sure the positive side (marked with a + symbol) faces up toward the spring contact inside the fob.

Common Key Fob Battery Types and Where They Fit

CR2032 is the most common. It's a 20 mm diameter coin cell, about 3.2 mm thick, and fits most key fobs from Honda, Toyota, Ford, Chevrolet, BMW, and many others. If your fob is a standard rectangular or oval shape about the size of a lighter, it almost certainly uses a CR2032.

CR2025 is slightly thinner (2.5 mm) than the CR2032 and is used in some Nissan, Mazda, and Volkswagen fobs. It will physically fit in a CR2032 slot, but it may not make reliable contact with the spring, so use the exact type your fob calls for.

CR2016 is even thinner and less common, but appears in some older or compact fobs. LR44 is a button-cell battery (smaller and rounder) used in a few luxury vehicles and some aftermarket fobs. BR2032 is a lithium version of the CR2032 and lasts longer, but costs more and isn't necessary for most people.

If you're unsure which type you have, take the old battery to a pharmacy, supermarket, or electronics store and ask the staff to match it. They can usually tell you in seconds.

Where to Buy Key Fob Batteries

You can buy key fob batteries at almost any retail location. Pharmacies like CVS and Walgreens stock them near the checkout or in the health and beauty section. Supermarkets carry them in the pharmacy or electronics aisle. Hardware stores like Home Depot and Lowe's have them in the electrical section. Online, Amazon, eBay, and Walmart sell them in bulk or single packs.

A single battery typically costs $3 to $8, depending on the brand and where you shop. Name brands like Energizer and Duracell cost slightly more than store brands, but the performance difference is minimal for key fob use. Buying a multipack (usually 4 or 5 batteries) is cheaper per battery if you have multiple fobs or want spares on hand.

Don't buy batteries from gas stations or convenience stores unless you're in a pinch — they're usually overpriced. If you're buying online, watch the shipping cost; a $4 battery with $6 shipping isn't a good deal.

How to Install a New Battery Safely

Before you open the fob, wash your hands or wear clean gloves. Oils from your skin can corrode the battery contacts over time. Once the fob is open, note which side of the old battery faces up — that's the positive side, marked with a + symbol. Remove the old battery by gently lifting it out or, if it's stuck, using a plastic spoon handle or coin to pry it up.

Wipe the metal contacts inside the fob with a clean, dry cloth or a pencil eraser to remove any corrosion. If there's white or blue-green crusty buildup, that's corrosion from a leaking battery, and cleaning it will improve the new battery's contact. Place the new battery into the holder with the positive side (+) facing up, toward the spring. The battery should sit flat and make contact with both the spring above and the metal contact below.

Close the fob and test it by pressing a button while standing near your car. You should hear the locks click or see the lights flash. If nothing happens, open it again and check that the battery is seated correctly with the + side up. If it still doesn't work, the battery may be defective — try a fresh one from a different pack.

Signs Your Key Fob Battery Is Dying

A dying key fob battery usually shows itself before it stops working completely. You may notice you have to press the button harder or multiple times to get a response. The range shrinks — you can unlock the car from 10 feet away instead of 30. The button response becomes sluggish or delayed.

Sometimes only one button stops working while others still respond, which usually means a corroded contact rather than a dead battery, but replacing the battery often fixes it anyway. If the fob hasn't been used in months, the battery may have self-discharged, so try a fresh battery before assuming the fob is broken.

Don't wait until the fob is completely dead to replace the battery. A dying battery can corrode inside the fob and damage the contacts, making the fob unreliable even after you install a new battery. If you notice the signs above, replace the battery within a week or two.

What to Do With the Old Battery

Coin-cell batteries contain lithium or alkaline chemicals and should not go in the trash. Most pharmacies and supermarkets that sell batteries will take old ones back for recycling at no charge — just ask at the customer service desk. Home Depot and Lowe's also have battery recycling programs.

If you can't return it to a store, check your city or county's hazardous waste collection schedule. Many areas hold collection days once or twice a year where you can drop off batteries, electronics, and other items for free. A quick search for "[your city] battery recycling" will show you the nearest drop-off location.

When to Call a Professional

If you open the fob and the battery compartment is flooded with corrosion, or if the case is cracked or won't close properly, the fob may need repair or replacement rather than just a new battery. A locksmith or car dealership can replace the battery for you if you're uncomfortable doing it yourself — this usually costs $10 to $20 in labor, plus the battery.

If you replace the battery and the fob still doesn't work, the problem is likely the fob's internal circuit or buttons, not the battery. At that point, a replacement fob (usually $50 to $200 depending on your vehicle) or a professional repair is your next step. Your car dealership can order a new fob and program it to your car, or a locksmith can do the same for less money in many cases.

Frequently Asked Questions

Can I use a different battery type if I can't find the exact one?

Not reliably. CR2032 and CR2025 are close in size, but CR2025 is thinner and may not make solid contact. LR44 is much smaller and won't fit the holder. Always use the exact type your fob calls for — the cost difference is only a dollar or two, and using the wrong battery can damage the fob's contacts or leave you stranded.

How long does a key fob battery last?

Most key fob batteries last three to four years with normal use. If you use your fob multiple times a day, it may last two to three years. If you rarely use it, it can last five years or longer. Leaving the fob in a hot car or exposing it to moisture shortens battery life.

Why did my new battery stop working after a few days?

The battery is probably installed upside down — the positive side (+) must face up toward the spring contact. Open the fob and flip the battery. If it still doesn't work, the battery may be defective or the fob's contacts may be corroded. Try cleaning the metal contacts with a pencil eraser and installing a fresh battery.

Can I use rechargeable batteries in my key fob?

Rechargeable batteries (NiMH) have a lower voltage than alkaline or lithium batteries and usually won't work reliably in key fobs. Stick with single-use alkaline (LR type) or lithium (CR or BR type) batteries. They're cheap enough that recharging isn't worth the hassle.

What if the battery compartment is stuck and won't open?

Try gently tapping the seam with a plastic tool or the handle of a screwdriver to loosen it. If that doesn't work, soak the fob in warm (not hot) water for a few minutes to soften any corrosion or adhesive, then try again. If it's still stuck, a locksmith or dealership can open it without damaging the fob.