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Due to aging of a battery over lifetime, the rated power and nominal energy capacity will be reduced compared with the initial rated power and capacity. These result in influences on the vehicle driving performance and fuel economy. To monitor and diagnose the aging of the battery, in this paper, the method of predicting the available rated power and energy capacity of Li-ion battery under in-vehicle condition is proposed. Under constant power test, available power is calculated from the estimated parameters using recursive least square method. Further, available energy capacity is evaluated through SOH(cn) defined by the ratio of initial state-of-charge (SOC) variation to present SOC (\GdSOC ⁿ /ΔSOC ⁿ ) variation under arbitrary in-vehicle driving cycles. To verify the proposed method, experiments for aging Li-ion battery are performed in hybrid electric vehicle.

Fuel cell is one of alternative power sources, which can replace the conventional internal combustion engine. But, it has some drawbacks such as low efficiency at high power output and inability of energy regeneration. So, hybridization of the fuel cell has been proposed to overcome these drawbacks. And the fuel cell hybrid system is preferred in a viewpoint of cost and performance. HMC's fuel cell hybrid system consists of a fuel cell, a battery, and a bi-directional dc/dc converter. Bi-directional dc/dc converter plays a key role that controls power distribution between fuel cell and battery. Conceptually, the fuel cell is main power source and the battery is auxiliary power source. In this paper, the power control strategy for fuel cell hybrid system is proposed to satisfy two control targets. One is to get high system efficiency and the other is to maintain battery's SOC(state of charge) in high efficiency region of the battery.