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Existing stop-start systems have several concerns such as take-off response, engine restart noise, high cost and system complexity. This paper describes a newly developed stop-start system that overcomes these concerns and can be used on high-volume production models at an affordable cost. The new system is based on a compact motor generator that allows cranking at restart and also functions as an alternator following engine start. A belt-driven system is used for restarting the engine to avoid noise from gear insertion and engagement. The motor generator is capable of high-speed operation for reducing engine startup time. Starting control has also been improved to achieve the shortest possible startup time in combination with a newly developed direct injection engine. Shortening the startup time tends to impair engine smoothness at restart. However, this concern has been resolved through cooperative control with the motor generator.

The performance capabilities which hold the key to the acceptance of electric vehicles (EVs) includes range and acceleration. Range can be effectively extended by increasing the size of the batteries used, but it requires a trade-off with acceleration performance which deteriorates due to the increased weight. The FEV-II and Prairie Joy EV exhibited at the 1995 Tokyo Motor Show were equipped with high-performance lithium-ion batteries that achieve both high energy and power densities, to provide an excellent balance of range and acceleration. Futher more, the batteries exceptionally high charging efficiency enables them to accept regenerative energy effectively. This feature improves range, and also allows the battery state of charge (SOC) to be determined accurately. This characteristic was used to develop a highly accurate battery model which was incorporated in a simulation program for predicting EV performance.