Modeling and Validation of Lithium-ion Polymer SLI Battery 2019-01-0594
Lead-acid batteries have dominated the automotive conventional electric system, particularly in the functions of starting (S), lighting (L) and ignition (I) for decades. However, the low energy-to-weight ratio and the low energy-to-volume ratio makes the lead-acid SLI battery relatively heavy, large, and shallow Depth of Discharge (DOD). This could be improved by replacing the lead-acid battery by the lithium-ion polymer battery. The lithium-ion polymer battery can provide the same power with lightweight, compact volume, and deep DOD which is essential requirement for engine idle elimination using start-stop function. This paper presents the modeling and validation of lithium-ion battery for SLI application in conventional vehicle. A simulation model of lithium-ion polymer SLI battery with battery management system is built in the MATLAB/Simulink environment. A SLI battery module (14.8V, 60Ah) consisting 12 lithium-ion polymer battery cells in series/parallel connection is experimentally tested using various charging/discharging currents in a temperature chamber. The experimental data is used to calibrate the model parameters for further validation. The simulation results show a 9% or less discrepancy in all continuous and pulse charge/discharge conditions. The developed battery model could provide a guideline to designing battery pack in the 12 voltage start-stop system or 48 voltage mild hybrid electric vehicle.