| Confront with severe challenges of the increasingly serious energy and environment problems, environment friendly and energy conserving cars has drawn worldwide attention and become the focus of research of governments and major automotive companies. Compared to electric vehicles and fuel cell electric vehicles, hybrid electric vehicles are predominant in dynamic performance, driving range, and ease of use, therefore it has great commercial value and a broad market prospect.Battery, as the main energy storage device in HEV has direct affects on the performance of HEV. Ni-MH battery power with high specific energy, high specific power, long cycle life, small environmental pollution, high safety and other advantages, becomes the preferred power for HEV. However, the performance of Ni-MH battery is affected greatly by temperature. Therefore, to design a good cooling structure, which distributes temperature uniformly in battery package, plays an important role in the protection of performance and reliability of battery.â‘ The heat transfer mechanism and basic performance of Ni-MH were analyzed theoretically, and test of charge and discharge characteristics was presented in this paper. It indicates that temperature and charge-discharge ratio are major factors which influence the performance of Ni-MH battery.â‘¡The main factors that influence the cycle life of Ni-MH battery were analyzed, and temperature was the major one. Some tests were carried out based on the theory of reliability and accelerated life testing. A formula was established to forecast Ni-MH battery cycle life under a specific temperature based on the test data, and a target of temperature uniformity was proposed to meet the requirement of Ni-MH battery cycle life for HEV.â‘¢The model was applied to simulate flowfield and temperature field of Ni-MH battery package cooling system, with the help of computational fluid dynamics (CFD) software FLUENT. And a scheme of structure was proposed, which has a good cooling effect and high temperature uniformity that meets the target.â‘£To verify the scheme, experiment of Ni-MH battery package thermal analysis was presented, according to the test method and criteria that car manufacturer supplied. Compared to the simulation results, test data was consistent with them well, and indicated the accuracy of the structure for Ni-MH battery package cooling system. This subject is an important element of the 863 electric vehicles major project -"The development of technology research platform for ISG Chang'an hybrid system"(2006AA11A107), which is in the"the Tenth Five-Year-Plan"and"the Eleventh Five-Year-Plan".
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