Smaller, hotter engine compartments, increased electrical loads, and stringent customer requirements place ever increasing demands on automotive battery performance. Current battery designs and shortcomings are discussed as well as the necessity for improved designs. Topics also include temperature effects, state of charge, charge efficiency, customer usage and requirements, battery age, and dealership handling practices. Present SAE test procedures are reviewed and new rating requirements are suggested to meet today's vehicle applications. Special dealership programs also reveal various methods to improve performance. In addition, power and thermal management for tomorrow's vehicles is discussed.The supporting documents are compiled from various studies conducted between 1984 and 1988 encompassing over 5,000,000 Chrysler vehicles. The data reflects direct comparisons from the field on a warm versus cold climate basis. Additional information on driving patterns and vehicle usage is also presented.