The basic steps to replace your BMW key fob battery

Most BMW key fobs use a coin-cell battery (usually CR2032 or CR2025) that you can replace yourself in about two minutes without tools. The process is the same across most BMW models from the past 15 years: locate the seam on the fob's edge, gently pry it open, remove the old battery, and slide in a new one with the positive side facing up.

You do not need to visit a dealer or buy special equipment. A new battery costs $3 to $8 at any pharmacy, grocery store, or hardware store. The hardest part is finding the seam—it is often thinner than you expect.

Key Takeaways

  • BMW key fobs typically hold a CR2032 or CR2025 coin-cell battery that slides out from the side or back of the fob.
  • You can open most fobs by locating a thin seam and gently prying with a flat object like a coin or plastic spoon.
  • The battery must go in with the positive (+) side facing up, or the fob will not work.
  • After inserting the new battery, press the fob buttons a few times to confirm it responds before closing it.
  • If the fob still does not work after a fresh battery, the problem is likely the circuit board, not the battery.

Finding the seam and opening your fob

Hold your BMW key fob in both hands and look for a thin line running around the edge. On most models, this seam runs horizontally across the middle of the fob, dividing the top and bottom halves. On some newer fobs, the seam runs vertically along one side. Run your fingernail along the edge to feel where the two pieces meet.

Once you locate the seam, use a flat object to gently pry the two halves apart. A coin works well—a penny or dime gives you enough leverage without being so thick that you risk cracking the plastic. A plastic spoon, a flathead screwdriver, or even a butter knife will work. Insert the edge into the seam and twist gently. You should hear a small click as the fob separates. Do not force it; if it is not opening, you may be prying at the wrong spot.

After the fob opens, you will see the battery sitting in a small metal holder. It is a thin, round disc, usually silver or gold in color. The holder has two small metal tabs that grip the battery's edges.

Removing the old battery and inserting the new one

Gently slide the old battery out of the metal holder. You may need to use your fingernail or the edge of a coin to lift one side slightly, then slide it out. Do not force it—the battery should slide out with light pressure.

Before you insert the new battery, check the markings on the old one. You will see a number like CR2032 or CR2025 printed on it. Buy a replacement with the exact same number. If you cannot read the old battery, CR2032 is the most common size for BMW fobs and will work for most models.

Slide the new battery into the metal holder with the positive side (marked with a +) facing up toward the top of the fob. The negative side (marked with a −) should face down toward the circuit board. This matters—if you insert it backward, the fob will not work. The battery should slide in smoothly and sit flat in the holder.

Testing the fob before closing it

Before you snap the fob back together, press each button on the fob a few times. You should feel the buttons click normally, and if your car is nearby, you can test whether the lock and unlock buttons work. If the fob responds, you are done. If nothing happens, remove the battery and check that the positive side is facing up.

If the fob still does not work after you have confirmed the battery is inserted correctly, the problem is likely inside the fob itself—either the circuit board is damaged or the metal contacts are corroded. In that case, a new battery will not fix it, and you will need to contact a BMW dealer or a locksmith who works with BMW fobs.

Closing the fob and checking the seal

Align the two halves of the fob so the seam lines up evenly on all sides. Press down firmly along the seam until you hear a click. The fob should feel solid and not have any gaps. If there are gaps, the two halves are not fully seated—press down again until they snap together completely.

Once the fob is closed, test the buttons one more time to make sure everything still works. The battery should last three to four years under normal use, depending on how often you use the fob.

What to do if the fob will not open

If you cannot find the seam or the fob will not budge, you may have a model with a different design. Some older BMW fobs have a small screw on the back instead of a snap-together seam. Look for a tiny screw head, usually Phillips or flathead. If you find one, use the appropriate screwdriver to remove it, then gently pry the back cover off.

If you still cannot open the fob after checking for both a seam and screws, stop trying. Forcing it will crack the plastic and damage the circuit board. At that point, your only option is a replacement fob from a BMW dealer or a third-party locksmith.

Where to buy a replacement battery

You can buy CR2032 or CR2025 batteries at any pharmacy (CVS, Walgreens), grocery store, hardware store (Home Depot, Lowe's), or online retailer. They are inexpensive—usually $3 to $8 for a single battery, or $5 to $15 for a pack of four. Some stores sell them in the watch or jewelry section, others in the electronics aisle. If you are not sure where to look, ask a store employee.

Avoid buying the cheapest batteries you can find. A mid-range brand like Energizer, Duracell, or Panasonic will last longer and is worth the small extra cost. Store batteries in a cool, dry place, and keep them away from metal objects that could short-circuit them.

Frequently Asked Questions

What battery does a BMW key fob use?

Most BMW fobs use either a CR2032 or CR2025 coin-cell battery. Check the old battery for the model number, or contact your BMW dealer with your car's year and model. CR2032 is more common and will work for most BMW models made in the last 15 years.

Can I use a different battery size if I cannot find the right one?

No. A CR2032 and a CR2025 are different thicknesses, and using the wrong size can prevent the fob from closing properly or cause the battery to lose contact with the metal tabs. Always use the exact size printed on your old battery.

Why is my fob not working even after I put in a new battery?

First, remove the battery and check that you inserted it with the positive (+) side facing up. If it is correct and the fob still does not work, the circuit board or metal contacts inside the fob may be damaged. A new battery will not fix internal damage—you will need a replacement fob.

How long does a BMW key fob battery last?

A new battery typically lasts three to four years with normal use. If you use the fob very frequently, it may last two to three years. If you rarely use it, it may last five years or longer. The battery will gradually weaken before it stops working completely.

Is it safe to replace the battery myself, or should I go to a dealer?

Replacing the battery yourself is safe and takes about two minutes. You do not need special training or tools. Dealers will do it for you, but they usually charge $50 to $100 for a service that costs you $5 in materials and two minutes of your time.