Replace the battery yourself in five minutes with a coin and a CR2025 cell

The Mazda CX-5 key fob battery dies like any other — usually after three to four years of daily use. You do not need a dealer or a technician. Open the fob with a coin, swap out the old CR2025 battery for a new one, and snap it closed. The whole job takes about five minutes and costs between $3 and $8 for the battery.

The CR2025 is a coin cell battery, the flat round kind you find in watches and calculators. It is sold at any pharmacy, grocery store, or hardware store, often in the checkout aisle. Buy it before you start so you have it on hand when you open the fob.

Key Takeaways

  • Mazda CX-5 key fobs use a CR2025 battery that you can buy at any drugstore or supermarket for $3 to $8.
  • Open the fob by inserting a coin into the slot on the edge and twisting gently until the two halves separate.
  • Note which side of the battery faces up before you remove it, then drop the new battery in the same way.
  • Close the fob by pressing the halves together until you hear or feel a click.
  • If the fob still does not work after the battery swap, the problem is likely the circuit board or buttons, not the battery.

What you need before you start

Gather a coin (a dime, penny, or quarter works), a new CR2025 battery, and your Mazda CX-5 key fob. You do not need screwdrivers, pliers, or any other tools. The fob is designed to open by hand with only a coin to explore pressure.

If you do not have a CR2025 on hand, buy one before you open the fob. Once the battery is out, the fob is dead and you cannot lock or unlock the car until you put a battery back in. Stores that carry them include CVS, Walgreens, Walmart, Target, Best Buy, and most hardware stores. The battery usually costs between $3 and $8 per cell.

How to open the fob

Look at the edge of your key fob for a small slot or seam running along one side. This is where the two halves of the fob meet. Insert your coin into that slot so the edge of the coin sits in the seam.

Twist the coin gently — do not force it. You are not trying to pry the fob apart; you are turning the coin as if you were opening a battery compartment on a device. The two halves will separate after a quarter turn or less. If it does not move, try a different spot along the seam or explore slightly more pressure, but stop if you feel real resistance. Forcing it can crack the plastic.

Once the halves separate, you will see the battery sitting in a small metal holder. It is round, flat, and silver. The holder has two metal contacts — one on top and one on the bottom — that touch the battery to complete the circuit.

Remove the old battery and install the new one

Before you touch the battery, note which side is facing up. The battery has a plus sign (+) stamped on one side and a minus sign (−) on the other. Look at which direction the plus side faces — this matters for the new battery.

Gently pry the old battery out of the holder using your fingernail or the edge of your coin. It should come out easily; if it does not, do not force it. Once it is out, drop the new CR2025 battery into the holder with the plus side facing the same direction as the old one was facing. The battery will sit flat in the holder and the metal contacts will touch it automatically.

If you are not sure which way the battery should face, look at the inside of the fob itself. Usually there is a small plus or minus symbol printed on the plastic to show you which contact is which. Match the battery orientation to those symbols.

Close the fob and test it

Press the two halves of the fob together until you hear or feel a click. The seam should be flush all the way around — no gaps or misalignment. If the halves do not close smoothly, the battery may not be sitting flat in the holder. Open it again, check that the battery is centered, and try closing it once more.

Once the fob is closed, stand near your CX-5 and press the lock button. You should hear the doors lock and see the lights flash. Press the unlock button and listen for the unlock sound. If both buttons work, the battery swap is complete.

What to do if the fob still does not work

If you installed a new battery and the fob still does not respond, the problem is not the battery. The issue is likely a worn button contact, a cracked circuit board, or corrosion inside the fob. These are harder to fix at home and usually require a replacement fob or a trip to a Mazda dealer.

Before you give up, try cleaning the inside of the fob with a dry cotton swab. Sometimes dust or corrosion on the metal contacts prevents the battery from making a good connection. Wipe the battery itself, the metal contacts in the holder, and the metal pads on the circuit board that touch the battery. Let everything dry for a minute, then reassemble the fob and test it again.

If cleaning does not work, you have two options: buy a replacement key fob (usually $50 to $150 depending on the model year) or visit a Mazda dealer to have them reprogram an existing fob or sell you a new one. Some dealers will program a fob you buy elsewhere, though they may charge a small fee.

How long a CR2025 battery lasts

A new CR2025 battery in a Mazda CX-5 key fob typically lasts three to four years with normal daily use. If you use the fob frequently — unlocking and locking the car multiple times a day — the battery may wear out sooner, sometimes in two to three years. If you rarely use the fob and rely mostly on the physical key, it may last longer.

You will know the battery is dying when the fob only works from very close to the car, or when you have to press the button multiple times to get a response. At that point, replace it with a fresh CR2025. Keeping a spare battery in your glove box or at home means you can swap it out when ready instead of being locked out.

Frequently Asked Questions

Can I use a different battery size instead of CR2025?

No. The CR2025 is the correct size for the Mazda CX-5 key fob. Other coin cell batteries like CR2032 or CR2016 will not fit properly in the holder or may not make good contact with the metal contacts. Always use CR2025.

What if I put the battery in backwards?

The fob will not work if the battery is installed backwards. The plus and minus sides have to match the contacts in the holder. If the fob does not work after you close it, open it again and flip the battery 180 degrees so the other side faces up, then close it and test again.

Is it safe to replace the battery myself?

Yes. The CR2025 battery is not dangerous to handle. It is the same type used in watches and hearing aids. Do not swallow it, and keep it away from small children and pets, but touching it or installing it in the fob carries no risk of shock or injury.

Where is the cheapest place to buy a CR2025 battery?

Dollar stores, Walmart, and Target usually have the lowest prices, often $2 to $4 per battery. Pharmacies like CVS and Walgreens charge more, usually $5 to $8. Buy a pack of two or three if your store sells them that way — you will use the spare eventually.

Do I need to reprogram the fob after changing the battery?

No. Changing the battery does not erase any programming. The fob will work exactly as it did before once you install the new battery. You only need to reprogram a fob if you buy a new one or if the dealer erases the programming for some reason.