The quickest way to find your key fob battery type
The battery your key fob needs is printed on the fob itself or in your vehicle's owner manual. Open the fob — most have a slot or button that releases the case — and look for a number stamped on the battery. That number tells you exactly what to buy. If you cannot open it without tools, your owner manual will list the battery type by your car's year, make, and model.
The most common key fob batteries are CR2032, CR2025, and CR2016. These are coin-cell batteries, small and flat like a dime. A few older fobs use AA or AAA batteries instead. Once you know the number, you can buy a replacement at any pharmacy, grocery store, or hardware store for between $3 and $8.
If you have lost your manual or cannot read the stamped number, your car dealership can tell you the battery type over the phone. You will need your vehicle identification number (VIN), which is on your registration or visible on the dashboard at the base of the windshield on the driver's side.
Key Takeaways
- The battery type is stamped on the battery itself inside the fob or listed in your owner manual by vehicle year and model.
- CR2032, CR2025, and CR2016 are the most common key fob batteries and cost $3 to $8 at pharmacies and hardware stores.
- If you cannot open the fob or read the number, your car dealership can tell you the battery type using your VIN.
- Coin-cell batteries last two to four years depending on how often you use the fob, and you can replace one yourself in under a minute.
How to open your key fob safely
Most key fobs split in half along a seam. Look for a small slot or indentation on the edge, and use a coin or a flat-head screwdriver to gently pry the two halves apart. Do not force it — if it does not move, you may be pushing in the wrong spot. Some fobs have a small button on the back that you press to release the battery compartment instead.
Once the fob is open, note which way the battery sits — the flat side usually faces up or down — because you will need to put the new one in the same way. Take a photo with your phone if you are unsure. The battery should lift out easily with your fingernail or a plastic tool. Avoid touching the new battery with bare fingers, because skin oils can reduce its lifespan.
If your fob has a rubber pad or circuit board, be careful not to bend or disconnect it. These parts are glued in place and do not need to come out. Once the new battery is seated, press the fob halves back together until they click.
Common key fob battery types and where they fit
| Battery Type | Size and Shape | Common In |
|---|---|---|
| CR2032 | 20 mm wide, 3.2 mm thick, coin-shaped | Most modern cars, key fobs from the last 15 years |
| CR2025 | 20 mm wide, 2.5 mm thick, coin-shaped | Some Honda, Toyota, and Nissan fobs |
| CR2016 | 20 mm wide, 1.6 mm thick, coin-shaped | Older fobs and some slim remote designs |
| AA or AAA | Cylindrical, standard size | Older or aftermarket key fobs |
Coin-cell batteries are measured in millimeters. The first two digits (20) refer to the width, and the last two (32, 25, or 16) refer to the thickness. If your fob is very thin or very old, you may have a CR2016 instead of the more common CR2032. Buying the wrong thickness will not damage anything, but the battery may not sit flush or may fall out.
The voltage on all these batteries is the same — 3 volts — so the main difference is physical size. Always match the exact number on your old battery to avoid fit problems.
How long a key fob battery lasts
A new coin-cell battery typically lasts two to four years in a key fob, depending on how often you press the buttons. If you use your fob multiple times a day, you may need a replacement sooner. If you use it only a few times a week, it may last longer.
You will notice the battery is dying when the fob has to be held closer to the car to work, or when you have to press the button multiple times. Some newer fobs have a low-battery warning light on the dashboard. Once the battery is dead, the fob will not work at all, but the car itself is not affected — you can still unlock it with your spare key or the physical key blade inside the fob.
Coin-cell batteries do not need to be recycled in most places, but some retailers like Best Buy and Home Depot have battery recycling bins near the entrance. Check your local rules, but throwing a dead coin-cell battery in the trash is generally safe.
What to do if the fob still does not work after replacing the battery
If you have put in a new battery and the fob still does not respond, the battery may not be making contact with the metal terminals inside the fob. Open the fob again and check that the battery is sitting flat and centered. If the terminals look dirty or corroded — they should be shiny metal — gently rub them with a clean, dry cloth or a pencil eraser.
If the fob still does not work, the problem is likely not the battery. The circuit board inside may be damaged, or the transmitter may have failed. In this case, you will need a replacement fob from your car dealership. Dealership fobs cost between $150 and $400 depending on your vehicle, but some people find cheaper aftermarket fobs online. Aftermarket fobs work with most cars, though you may need to program them yourself or have a dealer do it.
If only one button on the fob is not working while others do, the problem is usually a worn rubber pad under that button, not the battery. This is harder to fix at home and typically requires a replacement fob.
Storing spare batteries and fobs
Keep spare coin-cell batteries in a cool, dry place away from metal objects. Metal can short-circuit a battery if it touches both terminals at once. A plastic bag or battery case works well. Do not store batteries in a car, because heat can shorten their lifespan.
If you have a spare key fob, replace its battery at the same time you replace the one in your main fob. That way, if your primary fob dies unexpectedly, you have a working backup. Many people forget about spare fobs until they need them and find the battery is dead.
Frequently Asked Questions
Can I use a different battery type if I cannot find the exact one?
Not safely. Using the wrong voltage or size can damage the fob's circuit board or cause the battery to fall out while driving. Stick to the exact type stamped on the old battery. If you cannot find it locally, order online — most ship within two days.
Do I need to reprogram my fob after changing the battery?
No. Replacing the battery does not erase the fob's programming. It will work when ready once you close the case and test it. Reprogramming is only needed if you buy a new fob or if the fob loses its pairing with your car.
What if my key fob uses a battery I have never heard of?
Write down the exact number stamped on the battery and search for it online, or take a photo to a pharmacy or hardware store. Battery numbers are standardized, so any store that sells batteries can order it if they do not have it in stock.
Is it safe to touch a coin-cell battery with my bare hands?
It is safe, but not ideal. Skin oils can leave a thin film on the battery terminals and reduce contact. If you do touch it, wipe it gently with a clean cloth before installing it. This is a minor concern and will not cause when ready failure.