The BMW Group has launched two new Micro Hybrid functions in March 2007 in high volume models in order to reduce the fuel consumption: the Brake Energy Regeneration and the Auto Start Stop Function. Both functions are based on today's 14-volt vehicle electrical system and current series components. Some components were slightly modified or strengthened. An intelligent control algorithm for the alternator enables the Brake Energy Regeneration (BER). The Auto Start Stop Function (ASSF) reduces the idling fuel consumption by switching off the internal combustion engine in standing phases - provided that several constraints are given. A lead acid battery is still used as electrical energy storage, because of reasons of economy and package. As requirements to the battery are increasing, the BMW Group decided to use in connection with BER and ASSF the AGM1 technology. Up to now the tests and quality assurance measures have proved a good functionality and a battery life time equal to batteries in today's vehicles. In the following article, the two Micro Hybrid functions BER and ASSF will be explained in detail and the impact of these functions on the battery will be discussed.
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