Synthesis and Experimental Validation of Battery Aging Test Profiles Based on Real-World Duty Cycles for 48-V Mild Hybrid Vehicles

Electrified powertrains are gaining a larger market share thanks to stricter emission regulation requirements and customer preferences. Ranging from micro hybrid to all-electric powertrains, however, their success highly depends on satisfactory life-long performance of onboard energy storage systems. In order to guide the battery pack design and management, real-world representative cell aging tests are essential for a successful product development. Focusing on cycle aging, this study proposes a novel methodology based on Welch's power spectral density estimation to characterize real-world cell duty cycles and synthesize representative profiles for cell aging tests. A 48-V mild hybrid vehicle model is developed in MATLAB/Simulink to relate the real-world vehicle-level drive cycles to cell-level duty cycles. Compared to existing test profiles found in literature, the newly designed profiles take the impacts of road conditions and driver styles into consideration to account for real-world resemblance. Experimental aging test results with the proposed aging profiles on nickel manganese cobalt lithium-ion cells not only hint at the real-world aging scenarios, but also lay the foundation for future work such as aging modeling. Repeatability of testing results is also investigated in this study.