Replacing the key battery
DANGER Serious damage to health caused by swallowing batteries
Batteries contain toxic and corrosive substances. Swallowing batteries may cause serious damage to health.
There is a risk of fatal injury.
Keep batteries out of the reach of children.
If batteries are swallowed, seek medical attention immediately.
ENVIRONMENTAL NOTE Environmental damage due to improper disposal of batteries
Batteries contain pollutants. It is illegal to dispose of them with the household rubbish.
Dispose of batteries of in an environmentally responsible manner. Take discharged batteries to a qualified specialist workshop or to a collection point for used batteries. Requirements:
You require a CR 2032 3 V cell battery.
Mercedes-Benz recommends that you have the battery replaced at a qualified specialist workshop.
Remove the emergency key More.
Press release knob 
down fully and slide cover 
in the direction of the arrow.
down fully and slide cover in the direction of the arrow. Fold out cover in the direction of the arrow and remove.
in the direction of the arrow and remove. Remove battery compartment 
and take out the discharged battery.
and take out the discharged battery. Insert the new battery into battery compartment . Observe the positive pole marking in the battery compartment and on the battery when doing this.
. Observe the positive pole marking in the battery compartment and on the battery when doing this. Push in battery compartment .
. Re-attach cover and push it until it engages.
and push it until it engages.