Dynamic Internal Resistance Detection And Temperature Characteristic Analysis Of Lithium-ion Power Battery

The internal resistance of battery indicates the resistance of current flowing through the battery,which is an important parameter of the battery.It can evaluate the performance of the battery and reflect the health degree of the battery.The internal resistance test also plays an important role in the battery management system.However,internal resistance is uneasy to be measured,because it is able to be influenced by the temperature,battery material,battery charge and discharge and other factors.Thus,it is necessary to adopt appropriate measurement methods and instruments.By analyzing and comparing different battery models and measurement methods,Electrochemical Impedance Spectroscopy(EIS)was used as the internal resistance measurement method according to the temperature characteristics and dynamic internal resistance detection requirements of lithium batteries.TISEC(Temperature Influenced Synthesis Equivalent Circuit)model is used as the Equivalent model of the battery.According to the research requirements,a set of lithium battery internal resistance detection system is designed,which is mainly composed of Ac standard current source,battery to be tested,high-speed acquisition unit,control and data processing unit.The lithium battery internal resistance detection system uses virtual instrument technology to replace traditional detection instruments,which makes the detection process more flexible and fast,and also reduces the interference of some hardware circuits.As the core unit,the control and data processing unit controls the AC standard current source and the high-speed acquisition unit.The AC standard current source uses the RS-232 serial port to communicate with the control and data processing unit.The current source sends the stable AC excitation current to the battery under test in the way of frequency sweeping,and generates the excited voltage at both ends of the battery under test.The high-speed acquisition unit adopts data acquisition board NI-9215 and temperature sensor PT100 connected with lithium battery to collect voltage and temperature signals,and then transmits the voltage and temperature data to the control and data processing unit for operation processing and analysis.Lithium battery internal resistance testing system realized with lithium battery internal resistance,voltage,current value,and the real-time monitoring of parameters such as temperature,stable and reliable test results,according to the experimental data of lithium iron phosphate battery equivalent impedance curve and EIS curves,then the lithium batteries were tested under different temperature,it is concluded that the impedance of the lithium battery as the temperature decreases is obviously rising trend,the system expansion uncertainty is 3.94×10^-2m?.The extended uncertainty is 7.88×10^-2m?(=2).