Multi-step Fast Charging based State of Health Estimation of Lithium-ion Batteries
Dayu Zhang (Beijing Institute of Technology, TU Delft - DC systems, Energy conversion & Storage)
Zhenpo Wang (Beijing Institute of Technology)
Peng Liu (Beijing Institute of Technology)
Zian Qin (TU Delft - DC systems, Energy conversion & Storage)
Qiushi Wang (Beijing Institute of Technology)
Chengqi She (Hunan University of Science and Technology)
Pavol Bauera (TU Delft - DC systems, Energy conversion & Storage)
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Abstract
Accurately predicting the battery's aging trajectory is required to ensure the safe and reliable operation of electric vehicles (EVs) and is also the fundamental technique toward residual value assessment. As a critical enabler for mainstreaming EVs, fast charging has presented formidable challenges to health prognosis technology. This study systematically compares the performance of features extracted from the multistep charging process in the state of health (SOH) assessment. First, 12 direct features are extracted from the voltage curve, and the degradation mechanisms strongly correlated to these features are analyzed in detail. Integrating the degradation mechanism and correlation analysis, a data feature construction strategy is designed to categorize extracted features into groups. Then, the performance of different features extracted from the fast charging process in the SOH assessment is compared regarding estimation accuracy. Finally, the generalization and feasibility of the optimal data feature are verified with different fast charging protocols and training data sizes. The verification results indicate that the data feature representing fused degradation modes has excellent generalization and feasibility in SOH estimation, and the mean absolute error (MAE) and root-mean-squared error (RMSE) for various cells under different decline patterns are within 0.90% and 1.10% , respectively.