These instructions apply to the Mercedes E-Class Mk5 (W213) 2016-2023.
For other models, please choose your vehicle here.
The Mercedes E-Class W213 smart key uses a single CR2032 3V coin cell. You slide out the emergency key, open the housing, and swap the cell in a couple of minutes.
No programming is needed after a battery change. The key keeps its pairing.
How to change the E-Class key battery
- Press the release knob on the key and pull the emergency (mechanical) key fully out.
- Press the small release button and slide the battery cover in the direction of the arrow, then fold it out and remove it.
- Lift out the battery holder and remove the old CR2032 cell.
- Fit a new CR2032, observing the polarity marking in the holder (writing usually faces you).
- Refit the holder, reattach the cover until it clicks, and slide the emergency key back in.
If the car no longer locks or unlocks from the fob, a flat cell is the usual cause. You can still unlock with the emergency key and start the car by holding the fob against the marked position on the steering column.
A lost or broken key cannot be made at home. Only a Mercedes dealer can order and code a replacement key to your car.
What battery does a Mercedes E-Class key take?
One CR2032 3V lithium coin cell. The CR2450 some owners find in the manual is for the optional auxiliary-heater remote, not the car key.
Do I have to reprogram the key after changing the battery?
No. The transponder pairing is kept, so the key works immediately once the new cell is fitted correctly.
If a warning light stays on or a fault code appears afterwards, you can look the code up free on autodtcs.com.
Independent guide — not affiliated with Mercedes. Always follow your official service manual and safety precautions. Read our full disclaimer.