See also:

Mercedes-Benz M-Class Owners Manual
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Low-beam headlamps
To switch on the low-beam headlamps: turn the SmartKey in the ignition lock to position 2 or start the engine. Turn the light switch to . The indicator lamp in the instrument cluster light ...

Charging the battery
WARNING Never charge a battery still installed in the vehicle unless a battery charger unit approved by Mercedes-Benz is being used. Gases may escape during charging and cause explosions ...