During the time that the automotive battery was considered to be just a passive component in a vehicle electric power system, the battery industry's answer to all new challenges was constructive improvements. The emerging requirements of even higher function reliability cannot, however be met this way. A battery manufacturer of today has to give recommendations for the appropriate choice of the electrical architecture and has to design batteries that suit best the requirements. In addition, manufactures have to be engaged in the technology of battery management, of battery monitoring and state detection, and performance of prediction under future operation conditions. During service on-board a vehicle, battery performance undergoes significant changes, e.g., loss of storage capability, increase in internal resistance, and changes in voltage characteristics. These ageing processes have to be considered when the electrical architecture is being designed and management strategies are being formulated. Battery monitoring and state detection must be able to identify and quantify battery degradation. Moreover, performance prediction as well as management strategies have to be corrected on account of the changing battery characteristics. (c) 2004 Elsevier B.V. All rights reserved.