See also:

Malfunction
In the event of a failure or malfunction of the parking brake, secure the vehicle against rolling using a wheel chock, for example, when leaving it. ...

Maintenance
The battery is maintenance-free, i.e., the electrolyte will last for the life of the battery. Your service center will be glad to advise you on questions regarding the battery. ...

Switching off automatically
The system switches off and the LED goes out: After approx. 160 ft/50 m when driving forward. Above approx. 22 mph/36 km/h when driving forward. Switch on the system again if necessary. ...