Key battery
Important safety notes
WARNINGBatteries are toxic and contain corrosive substances. Therefore, keep batteries out of the reach of children.
If a battery is swallowed, seek medical attention immediately.
Environmental protection
Batteries contain pollutants. By law, they must not be disposed of with household waste.
They must be collected separately and recycled in accordance with environmental protection regulations.
Dispose of batteries in accordance with environmental protection regulations. Take used batteries to a qualified workshop or a used battery collection point.
Preferably have the batteries replaced by a qualified workshop.
Checking the battery

- Press the button
or the button
.
If the battery is good, battery indicator 1 lights up briefly.
If battery indicator 1 does not light up briefly, the battery is discharged.
- Replace the battery.
or the button
causes- locking or
- unlocking the vehicle
You can obtain a battery from any qualified workshop.
Replacing the battery
- You need 1 button battery, 3 V, type CR 2025.
Remove the emergency key from the key.

- Press the emergency key 2 into the key opening (arrow) until the battery compartment cover 1 opens 1.
When doing so, take care not to block the opening of the cover. - Remove battery compartment cover 1.

- Tap the key against the palm of your hand to remove battery 3.
- Insert the new battery with the positive terminal facing up. Use a lint-free cloth for this.
- Make sure the battery surface is free of lint, grease or other dirt.
- Insert the front tabs of battery compartment cover 1 into the housing, then press the cover closed.
- Put the emergency key back into the key.
- Check that all buttons on the key work correctly on the vehicle.
Test yourself
A quick Mercedes-Benz B-Class quiz: every answer comes with an explanation and a link to the manual page.