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This paper begins with a comparison of the automotive power supply and loads in the early 1950's (near the end of the six-volt era) to the modern counterpart in the early 1990's (possibly near the end of the 12-volt era). A typical power supply specification sheet is developed based on the in-vehicle performance characteristics. From this summary, two attributes are noted: first, the system voltage is not very stable and second, transient protection is limited. With this awareness and the knowledge that the power supply of the future will need architectural change, a review of the design assumptions using a total system view and a long term outlook is advanced. Using a rule based design process and employing available technology to enhance the power system architecture, a number of elements are proposed for consideration in new designs.

During the past two years, a group of interested engineers have assembled and formed the SAE Dual/High Voltage study group. The participants have an awareness that today's 12 volt electrical power system may not be able to keep pace with forthcoming electronic technology and continued increasing electrical loading in modern automobiles. Their purpose is to address the implications of higher and/or multiple voltages and to make recommendations that will facilitate some acceptable global standards. This paper traces the course of the study committee work, reports on their deliberations and interim conclusions, and outlines items currently under study and discussion. Of special interest are the recommendations on the limit for an admissible contact voltage and the schematic diagrams of electrical systems discussed by committee members as possible candidates for the vehicle of the future.