| Power battery pack for pure electric vehicles is researched in this paper.NCR18650PF ce lls are chose as the basic unit and the multi-layer battery system architecture from battery pac k to battery system is designed. Based on this structure, the sample of battery pack is trial-pro duced for researching its heat dissipation characteristics and dynamic properties. The main w orks done in this paper are as follow:(1) The mechanical design and manufacture of battery pack:According to the requirements of the pure electric vehicle, the basic parameter of the power battery system is calculated and the battery pack architecture is designed,18 cells compose a battery module in parallel and 24 modules compose the battery pack in series. The mechanical design of battery module mainly includes checking the current-carrying capacity for collector piece and fixing cells.In the design process of battery pack, the subject fully considers battery module's fixation, the power wire's current capacity and the heat dissipation sturcture of battery pack.The specific energy of the final pack is 102.337 W·h/kg.(2)The thermal behavior of battery cell and battery pack:In this part, some experiments were carried out to analyze the characteristics of cell including current constant discharging characteristic, battery temperature characteristics and the internal resistance of cell at room temperature.Based on the three dimensional thermal model, the heat generation model simulation at different discharge rates is completed.Compared to the experiments' results, the thermal model is proved to be correct. Based on the heating model, two-dimensional thermal model is established to check the the cooling system when the battery is discharging at 1C rato.The maximum temperature rises by 10?,indicating that the cooling system could depress temperature.(3) Dynamic properties of battery pack:In this part, the free modal experiment of battery was carried out to obtain the natural frequencies and mode shape of battery pack.Compared to the results of the test, the finite model is proved to be correct.Based on the finite model, the finite model of battery box is established. The strength anslysis of battery box is done when car running on the uneven road.The free modal analysis of battery pack is completed to obtain the first natural frequency and the first frequency is 58.12Hz which avoids excitation frequency ranges of the roads. According to the requirements of battery box testing, harmonic analysis of battery is conducted to check the strength of battery box.Finally, the fixed frequency vibration analysis is used to study the dynamic characteristic of battery pack and verify the fatigue life of battery pack. |
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