Stochastic Operational Driving Cycles of an Electric Vehicle Battery System for Degradation Experiments

초록

This study proposes a novel framework for designing battery degradation experiments. The proposed framework aims to evaluate the lifetime of a lithium-ion battery (LIB) pack in electric vehicles (EVs) under stochastic operational conditions by comprising two phases. First, the consumption scenario is established through an in-depth analysis on the charging characteristics of EVs under various road types. This scenario aims to replicate the actual charging and discharging processes based on the daily battery consumption patterns of EVs. Second, an operational profile is generated to represent the driving characteristics of the LIB pack in EVs through two steps. Specifically, the first step generates a virtual speed profile to represent the dynamic characteristics of EVs under stochastic operational conditions. The second step then converts this speed profile into a discharging current profile in consideration of the mechanical and electric characteristics of the EVs. Comprehensive analysis on the operational profiles generated using actual driving data demonstrates the representativeness and high fidelity of the proposed framework. The degradation experiment with the proposed framework further confirms the time efficiency in that the proposed framework achieves 2.94 times higher efficiency in terms of time and labor consumption compared with the field experiment. This achievement suggests that the proposed framework could serve as a novel tool for designing battery degradation experiments that replicate the stochastic operational conditions of EVs.

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