Replace the Key Fob Battery

If the Comfort Access remote on your BMW 5 Series (F10/F11/F18, 2010–2017) has become weak — you have to be close to lock or unlock, or a “key battery low” message has appeared — the fob’s coin cell needs replacing. The F10 key uses a CR2450 cell and the job takes a couple of minutes. This guide shows how.

What You Need

• One fresh CR2450 3 V lithium coin cell.
• Clean, dry hands — skin oils shorten coin-cell life.

How to Replace the F10 Key Battery

1. Release and slide out the mechanical blade: press the small button on the side of the fob and pull the metal emergency key out.
2. With the blade removed, the cover at that end of the fob comes away — ease it off (some F10 keys split along the seam; others have a sliding back cover).
3. Lift out the old CR2450 cell — note which way up it sits (usually positive towards the back of the fob).
4. Fit the new cell the same way round, with the positive (+) side up as the original sat.
5. Refit the cover and slide the mechanical blade back in until it clicks.
6. Test lock/unlock and Comfort Access from a normal distance.

Does It Need Programming?

No — replacing the coin cell does not affect the fob’s pairing, so the key keeps working immediately. A brand-new or replacement key must be ordered and programmed by BMW with a diagnostic tool — that part is not owner-doable.

Frequently Asked Questions

What battery does the F10 key take?

A CR2450 3 V lithium coin cell. (Some very early keys are sealed rechargeable units that charge in the slot — if yours has no removable cell, it’s the rechargeable type and isn’t a DIY swap.)

Will the car still start if the fob battery dies?

Yes. Hold the fob against the marked spot on the steering column (or slot it in, where fitted) and press start — the car reads the transponder directly. The blade in the fob unlocks the driver’s door.

My key has no removable battery — why?

The earliest F10 Comfort Access keys used a rechargeable cell that tops up while the key is in the ignition slot or near the car. Those aren’t replaced at home; if it won’t hold charge, BMW supplies a new key.

The remote still won’t work with a fresh cell — now what?

Re-open it and check the cell orientation and that the contacts are clean. If it’s still dead, the fob may have an internal fault and need replacing by BMW.

To clear a service reminder after maintenance, see our BMW 5 Series service indicator reset guide. For warning lights, look up the code on autodtcs.com.