Volkswagen's battery energy management system automatically ensures sufficient battery power to start the engine, based on the battery charge state and the temperature. It is designed to be effective even when the car is left unused for a long time. Modern cars are constantly tapping the battery's energy, even when not in operation, with systems like the traffic news memory and anti-theft alarm system. If the charge level becomes critical, the system gradually shuts down the car's non-operative consumption. It monitors the battery voltage level and the charging activity while you are driving. If necessary, the idle speed is increased slightly to increase the alternator's charging output. In extreme cases, very high-consumption components such as the seat heating are temporarily shut down, but during normal driving this interruption is so brief as to be unnoticeable.
Article source: www.volkswagen.co.uk