2001 Mercedes C-Class Owner's Manual - Page 326

Therefore, we strongly recommend that you have the battery charge checked frequently, and corrected if necessary, especially if you use the vehicle less than approximately 200 miles (300 km) per month, mostly for short distance trips, or if it is not used for long periods of time. Only charge a battery with a battery charger after the battery has been disconnected from the vehicle's electrical circuit. Always disconnect the battery negative lead first and connect last. When removing and connecting the battery, always make sure that all electrical consumers are off and the electronic key is in starter switch position 0. The battery, its filler caps, the vent tube and the opposite plug must always be securely installed when the vehicle is in operation. While the engine is running the battery terminal clamps must not be loosened or detached, otherwise the generator and other electronic components would be damaged. Removal of filter box: Release three clamps (1) and remove filter box. Installation of filter box: Install filter box properly and secure with three clamps (1). Battery Instruments and controls Operation Driving 317 Instrument cluster display Practical hints Car care Technical data Index