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This study involves the battery requirements for a fuel cell-powered hybrid electric vehicle. The performances of the vehicle [a 3200-lb (1455-kg) sedan], the fuel cell, and the battery were evaluated in a vehicle simulation. Most of the attention was given to the design and performance of the battery, a lithium-ion, manganese spinel-graphite system of 75-kW power to be used with a 50-kW fuel cell. The total power performance of the system was excellent at the full operating temperatures of the fuel cell and battery. The battery cycling duty is very moderate, as regenerative braking for the Federal Urban Driving Schedule and the Highway Fuel Economy Test cycles can do all charging of the battery. Cold start-up at 20°C is straightforward, with full power available immediately.

In this study, three batteries were designed and these designs were evaluated in a hybrid vehicle simulation program. The battery designs were based on laboratory tests of 18650 cells for which a Lumped Parameter Battery Model was employed to correlate the cell impedance data. The three battery designs were each tested on three driving cycles, the Federal Urban Driving Schedule, the Highway Fuel Economy Test, and a special cycle developed to test the full power of the vehicle. The results of these simulation tests showed that the battery impedances were low for much of the time because the discharging and charging currents are not maintained at high levels for long periods of time on these cycles. For these conditions, the rates of heat generation in the batteries that were calculated by the simulation programs were low and may not be a serious problem.