Aging Simulation of Electric Vehicle Battery Cell Using Experimental Data 2021-01-0763

The adoption of lithium-ion batteries in vehicle electrification is fast growing due to high power and energy demand on hybrid and electric vehicles. However, the battery overall performance changes with time through the vehicle life. This paper investigates the electric vehicle battery cell aging under different usages. Battery cell experimental data including open circuit voltage and internal resistance is utilized to build a typical electric vehicle model in the AVL-Cruise platform. Four driving cycles (WLTP, UDDS, HWFET, and US06) with different ambient temperatures are simulated to acquire the battery cell terminal currents. These battery cell terminal current data are inputs to the MATLAB/Simulink battery aging model. Simulation results show that battery degrades quickly in high ambient temperatures. After 15,000 hours usage in 50 degrees Celsius ambient temperature, the usable cell capacity is reduced up to 25%. Driving cycle simulations indicate that aggressive acceleration and decelerations quickly shorten the battery life. The effects of Depth of Discharge (DOD) before each recharge on the battery aging is also investigated. Simulation results show that cell degradation rate increases with larger DOD. After 15,000 hours usage, the battery remaining capacity is about 10% more if the battery is recharged to full with 65% DOD comparing to that with 95% DOD. This investigation presents that smooth driving without hard acceleration and deceleration, driving at ambient temperature around 25 degrees Celsius, and fully recharging the battery pack at shallow DOD level will slow down the aging process of the electric vehicle battery pack.