A First-Order Transient Response Model for Lithium-ion Batteries of Various Chemistries: Test Data and Model Validation

In this report, a first-order transient response battery model is presented. The model can be utilized in the simulation of electric vehicles to calculate the battery voltage for dynamic operation of an electric-hybrid vehicle on various driving cycles. The battery model requires knowledge of the battery Ah capacity, the hyst-SOC-OCV curve and parameters of the equivalent circuit (R0, R1, tau1). A number of lithium-ion cells of the different chemistries were tested on charge / discharge step current profiles to determine the circuit parameters for a series of states-of-charge. The cells were then tested on the MHC and DST variable current profiles to determine how well the model predicted the response of the cells to the dynamic profiles. For DST test, the output voltages from the model for all the eight cells tested followed the test voltages well with the errors being relatively small –usually less than 20mV – except for SOC near to 1 and O. For MHC profile, the tests were performed at a nearly fixed SOC and the errors were particularly small. The study shows that over most of the useable state-of-charge range, the first-order transient model can be applied to predict the voltage response of lithium-ion batteries to dynamic charge and discharge currents encountered in vehicle applications.