You can replace a BMW key fob battery yourself in about five minutes

Most BMW key fobs use a coin-cell battery—usually CR2032 or CR2025—that you can buy at any drugstore or supermarket for a few dollars. The battery sits behind a cover that either slides off or pops out with gentle pressure. Once you remove the old battery, drop in the new one with the positive side facing up, close the cover, and test the buttons. The whole job takes longer to find the right battery than to install it.

You do not need any special tools. A fingernail or the edge of a coin works to pry open the cover if it is tight. If your key fob has stopped responding to button presses or only works when held at certain angles, a dead battery is the most common cause.

Key Takeaways

  • BMW key fobs typically use CR2032 or CR2025 coin-cell batteries, which cost $3 to $8 and are sold at pharmacies, grocery stores, and hardware stores.
  • The battery cover slides off or pops out with light pressure—no tools required, though a coin edge helps if the cover is tight.
  • Install the new battery with the positive (+) side facing upward, which is the side you see when you look down at it.
  • Test all buttons (lock, unlock, trunk, panic) before putting the fob back in your pocket to confirm the battery is seated correctly.
  • If the fob still does not work after a new battery, the circuit board or buttons may be damaged and the fob may need replacement.

Identify which battery your BMW key fob uses

The easiest way to find the right battery is to open the fob first and look at the old battery. The battery type is printed on the metal side—you will see "CR2032" or "CR2025" or occasionally "CR2016". Write down the number before you close the fob again.

If you want to know before opening the fob, you can search online for your BMW model year and "key fob battery type." Most BMW fobs from 2000 onward use CR2032, which is the most common size. CR2025 is slightly thinner but works in the same slot. Do not buy CR2016 unless you see it printed on your old battery—it is too thin and will rattle inside the fob.

Open the key fob cover

Look at the edge of your key fob for a small seam or slot. Most BMW fobs have a cover that slides off sideways—usually toward the panic button side. Hold the fob in one hand and use your thumbnail or a coin to gently push the cover in the direction the seam runs. Do not force it; if it does not move, try the other direction.

Some newer BMW fobs have a cover that pops straight out from the back. If you see a small notch or indentation on the back, insert a coin edge into it and gently pry upward. The cover will pop free. Once it is loose, set it aside where you will not lose it—the cover is straightforward to misplace and costs $15 to $30 to replace.

Remove the old battery and insert the new one

Once the cover is off, you will see the battery sitting in a metal holder or plastic slot. The battery is usually held in place by a small metal clip or spring on one side. Gently lift or slide the battery out. If it is stuck, use a plastic spoon handle or the edge of a coin to nudge it—do not use a sharp metal tool that could scratch the circuit board.

Before you insert the new battery, check the orientation. The positive side (marked with a +) should face upward—toward you when you look down at the open fob. Slide or drop the new battery into the slot. You should hear or feel a small click as the metal clip or spring snaps over the edge of the battery. If the battery sits loose, it is probably upside down; flip it and try again.

Close the fob and test all buttons

Slide or press the cover back into place until it sits flush with the fob body. You should hear a soft click. Do not force it; if the cover does not slide smoothly, the battery may be sticking out and preventing the cover from closing. Open the fob again, check that the battery is seated all the way down, and try closing it once more.

Stand near your BMW and press each button on the fob: lock, unlock, trunk, and panic (if your fob has one). The car should respond to each press. If one button does not work, the battery may not be making full contact with the circuit board. Open the fob again and make sure the battery is sitting flat and the metal clip is holding it down. If all buttons work, you are done.

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 circuit board may have corroded, or one of the rubber buttons may have worn through. Water damage is also common—if your fob has ever gotten wet, the circuit board may be corroded even if it looks dry on the outside.

You have two options: buy a replacement key fob (usually $50 to $150 depending on your BMW model) or take the fob to a BMW dealer to have it repaired. A dealer can sometimes clean and repair a corroded board for $40 to $80, though they may recommend replacement instead. If you buy a replacement fob, you will need to have the dealer program it to your car—you cannot program a BMW key fob yourself.

Where to buy a replacement battery

CR2032 and CR2025 batteries are sold everywhere: pharmacies (CVS, Walgreens), grocery stores, hardware stores (Home Depot, Lowe's), and online (Amazon). A single battery costs $3 to $8 depending on the brand. Name brands like Duracell and Energizer last longer than generic store brands, but any CR2032 will work in your fob. Buy a pack of two or four if you have multiple key fobs or want a spare on hand.

Do not buy batteries from gas stations or convenience stores unless you are in a hurry—they are usually marked up to $10 or more. If you order online, factor in shipping time; a pharmacy visit is faster if you need the fob working today.

Frequently Asked Questions

How long does a BMW key fob battery last?

A CR2032 battery in a key fob typically lasts three to four years with normal use. If you press the buttons many times per day, the battery may die sooner. Cold weather also drains batteries faster. If your fob is older than four years and the battery is dead, replacing it may buy you another three to four years before the next replacement.

Can I use a different battery size if I cannot find CR2032?

CR2025 is slightly thinner but will work in most BMW fobs designed for CR2032. CR2016 is too thin and will not make proper contact. Do not use AA, AAA, or any other size—they will not fit. If you cannot find CR2032 or CR2025 locally, order online rather than substituting a different size.

What if I lost the fob cover when I opened it?

You can order a replacement cover from BMW or from third-party sellers on Amazon or eBay for $15 to $30. Until it arrives, you can use the fob without the cover—the battery will stay in place as long as you do not drop it. Tape the cover slot closed with electrical tape if you want to protect the circuit board from dust or moisture.

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

No. Changing the battery does not erase the fob's programming. Once the new battery is installed and the fob responds to button presses, it will work exactly as it did before. You only need to reprogram a fob if you buy a new one or if the fob loses its programming for another reason.

Why does my fob only work when I hold it a certain way?

This usually means the battery is not making full contact with the circuit board. Open the fob and make sure the battery is sitting flat in its slot and the metal clip or spring is holding it down firmly. If the battery is seated correctly and the problem persists, the circuit board may be damaged or corroded, and the fob may need replacement.