You can replace a BMW key fob battery yourself in about five minutes with a coin and a replacement battery

BMW key fobs use a coin-cell battery that dies every few years. You do not need to visit a dealer — the battery is accessible from the outside of the fob, and the replacement battery costs between $3 and $8 at any pharmacy, supermarket, or hardware store. The whole job takes longer to find a coin than to do the work.

The exact battery type depends on your BMW model year and fob design. Most recent BMW fobs use a CR2032 battery, but some older models use CR2025 or CR2016. The easiest way to find out which one you need is to look at the battery currently in your fob — the type is printed on it — or to call your BMW dealer with your vehicle identification number (VIN) and ask what battery your key fob takes.

Key Takeaways

  • Most BMW key fobs use a CR2032 coin-cell battery that you can buy at any pharmacy or supermarket for $3 to $8.
  • You open the fob by inserting a coin into the slot on the edge and twisting gently until the two halves separate.
  • The battery sits in a metal holder; you lift it out, replace it with the new one in the same direction, and snap the fob back together.
  • If your fob stops working after you replace the battery, the problem is usually a battery installed upside down or a fob that needs reprogramming to your car.

What battery type your BMW key fob uses

The battery type is printed on the battery itself. If your fob is still working, open it and look at the current battery — you will see a code like CR2032, CR2025, or CR2016. Write down that code and buy the same type as a replacement.

If your fob is completely dead and you cannot open it, or if you want to know before you start, call your BMW dealer with your VIN. They can tell you the battery type in one call. You can also check your owner's manual — some BMW manuals list the battery type in the key fob section.

CR2032 is by far the most common. If you are buying a battery without knowing the type, CR2032 is the safest guess for any BMW made in the last 15 years.

How to open your BMW key fob

Look at the edge of your key fob. You will see a thin slot running along one side — this is where the two halves of the fob meet. Insert a coin (a dime or penny works) into that slot, flat side first.

Turn the coin gently, as if you are opening a jar. Do not force it. The two halves of the fob will separate after a quarter turn or so. Once you see a gap, you can usually pull the halves apart by hand.

Inside, you will see a metal battery holder with the coin-cell battery sitting in it. The battery is usually held in place by a small metal clip or tab. You do not need to remove this clip — you can lift the battery out from under it.

Removing and replacing the battery

Lift the old battery out of its holder. Note which side was facing up — the side with the + symbol should face toward you (or toward the outside of the fob, depending on how your fob is designed). This matters for the new battery.

Take your new battery and place it in the holder with the + side facing the same direction as the old one was facing. The battery should sit flat and snug in the holder. If it is loose or tilted, it will not make good contact and your fob will not work.

Close the fob by pressing the two halves together until you hear a click. You do not need the coin anymore — the fob will snap shut on its own.

Testing your fob after battery replacement

Stand near your BMW and press any button on the fob — lock, unlock, or trunk. You should see the lights flash on your car and hear the locks respond. If nothing happens, open the fob again and check that the battery is sitting flat in its holder and facing the right direction (+ side up).

If the battery is in correctly and the fob still does not work, the fob itself may be damaged, or your car may need the fob reprogrammed. Most BMW models require reprogramming if the fob has been completely dead for more than a few weeks. You can reprogram it yourself by sitting in the driver's seat, inserting the key in the ignition, turning it to the "On" position without starting the engine, turning it back to "Off", and repeating this cycle several times until the doors lock and unlock on their own — this signals that the fob is reprogrammed. If that does not work, your BMW dealer can reprogram it for you.

Where to buy a replacement battery

Coin-cell batteries are sold at pharmacies (CVS, Walgreens), supermarkets (most have a pharmacy section), hardware stores (Home Depot, Lowe's), and online retailers. A single CR2032 battery usually costs $3 to $8 depending on the brand and where you buy it. Some stores sell them in multipacks for slightly less per battery if you want spares.

You do not need a special BMW battery — any CR2032 (or whatever type your fob uses) from any brand will work. Duracell, Energizer, and store brands all perform the same way in a key fob.

What to do if your fob has other problems

If your fob has physical damage — a cracked case, water inside, or buttons that do not click — a new battery will not fix it. A damaged fob usually needs to be replaced entirely. Your BMW dealer can order a replacement fob and program it to your car, though this costs more than a battery.

If your fob works sometimes but not always, the problem is often a weak battery connection inside the fob. Open the fob again and make sure the battery is sitting completely flat in its holder and that the metal clip or tab is not bent. If the clip is bent, you can gently straighten it with a small tool, but be careful not to damage the fob's circuit board.

Frequently Asked Questions

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

No. Different coin-cell batteries have different thicknesses and voltages. Using the wrong type can damage your fob's circuit board or cause the buttons to stop working. Always use the exact type printed on your old battery or recommended by your dealer.

How often do BMW key fob batteries need to be replaced?

Most coin-cell batteries last three to four years in a key fob, depending on how often you use the fob. If you use your fob many times a day, the battery may last only two years. If you use it rarely, it may last five years or more.

What if I drop the battery or lose it while replacing it?

Coin-cell batteries are small and straightforward to lose. If you drop yours, buy a new one — they are inexpensive. Do not try to reuse a battery that has been dropped or exposed to water, as it may be damaged inside even if it looks fine.

Will replacing the battery erase my fob's programming?

No. Replacing the battery does not erase the fob's programming to your car. However, if your fob was completely dead for several weeks, your BMW may have cleared the programming as a security measure, and you will need to reprogram it.

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

Usually not, unless the fob was dead for an extended period. If your fob does not work after you replace the battery and the battery is installed correctly, try the reprogramming steps: turn the key to "On" and "Off" repeatedly in the ignition until the doors lock and unlock on their own.