Research On Health Level Detection Circuit And Evaluation Method Of Lithium-ion Battery

Lithium-ion batteries have become the ideal choice for power sources because of high power density and high energy density.However,the battery has a certain degree of danger as a high ratio energy storage device.The timely detection of abnormal battery conditions and intervention during use is a growing concern for consumers.The complex electrochemical reaction inside the battery cannot be directly measured by the meter,but we can estimate its state by identifying the equivalent parameters of the battery.Considering the possible self-discharge phenomenon in the whole life cycle of the battery,a battery equivalent circuit model with a shunt resistor is selected.The smaller the shunt resistance value,the more serious the short-circuit fault in the battery and the greater the self-discharge current.Then,combined with the electrical characteristics of the battery under pulse current excitation,the equivalent circuit model is simplified to reduce the complexity and calculation of parameter estimation,and the expressions of battery electromotive force and shunt resistance are derived.According to the needs of the pulse excitation experiment,a series battery pack detection circuit with high precision,high sampling frequency,high cost performance and small size is designed based on Renesas MCU.The component selection and hardware circuit design are divided into modules,and the software system is developed.Through the data collection of the battery static measurement and the dynamic process of charging and discharging,the performance test and correction of the detection cir cuit are completed,and it is verified that the detection circuit can adjust the sampling frequency according to different requirements,realize the automatic synch ronous detection of multichannel voltage and series current,and compare the results.Feedb ack to the host computer.In order to verify the accuracy of the parameter identification method,based on the internal short circuit substitution experiment,diffe rent degrees of internal short circuit were simulated for batteries with different states of charge.The calculation results show that the algorithm has a good diagnostic effect on the short-circuit faults within 10Ω-500Ω.Combined with the analysis of the electrical characteristics of the battery pack with internal short circui t under the intermittent constant current discharge condition,it is proposed that the static parameter shunt resistance value,which charact erizes the current self-discharge degree of the battery,and the minimum cell voltage and the cell dynamic consistency describing the battery dynamic consistency are proposed.The difference of the average voltage and its rate of change are used together a s three indicators to evaluate the battery health level,which improves the battery state evaluation method.