Development Of Test System For New Energy Vehicle Power Battery

Whether in the field of new energy vehicles or in the field of energy storage,people pay more attentions about how to evaluate the performance of power battery in a fast and efficient way.Power battery direct current internal resistance(DCIR)and alternating current internal resistance(ACIR)are important factors which are related to power battery performance.The test system of power battery and battery cell is developed based on Labview in this thesis.The internal resistance characteristics of the battery are studied by using the battery test system,which can provide support for the establishment of a system which can rapidly evaluate the performance of power battery.The power battery test system includes two parts:power battery pack test system and battery cell test system.According to different test objects to complete the system design,system hardware selection and so on.The main functions of the test system in this thesis include device control,data monitoring,DCIR test and data storage.The characteristics of internal resistance of battery cell are studied in this thesis.The test ways of DCIR for power battery mainly include HPPC made by USA,JEVS-D713 made by Japan and test method provided in the“863”program maded by China and so on.These three methods have something in common that they get DCIR by single current step test.In this thesis,double current step test is used to evaluate the DCIR based on the IEC-61960,its content is extended during the test,DCIR gotten by single current step test(static)and double current step test(dynamic)are compared in this thesis.The change trend of DCIR is studied under dynamic pulse condition which can provide data support for evaluating battery status under real vehicle condition.We generally get ACIR by two ways,the test system with disturbance source(TSWDS)or without disturbance source.TSWDS is studied based on Multisim,the characteristics of isolation capacitance is analyzed under constant voltage disturbance or constant current disturbance.Isolation capacitance has great influence on TSWDS,when develope the TSWDS,should pay more attention on it.The power battery test system developed in this thesis can be divided into two modes:automatic test mode and manual test mode.Datas from battery management system(BMS)can be monitored at a real time during the test.The operating mode editor module is developed to edit complex test files,the test files can be stored as text document.The test files viewer module is developed to facilitate the inspection of edited test files.Manual test mode mainly serves for battery cell test,including charge,discharge,SOC adjustment,DCIR test,data storage and other functional modules.By comparing dynamic DCIR and static DCIR,the two test ways have a certain differences,but they have a similar change trend.Under the condition of dynamic pulse discharge,the dynamic DCIR changes with SOC in accordance with the exponential change rule and the R-square value is above 90%.The relationship model between ACIR and the total impedance and internal structure impedance at different SOC states are established based on the second-order RC equivalent circuit model in this paper.The model is verified by 18650 and square battery,the R-square value is above 70%.It is good for understanding the battery state by studying the relationship between ACIR and the impedance of the battery model.The dynamic DCIR and ACIR under different cycles are analyzed at the same time.At last,introducing what can be done continuely based on the study at the end of this thesis.