Mathematical Assessment of the Reliability of Battery Systems of Electric Transport Rolling Stock Taking into Account Thermal Barriers

Abstract

A comprehensive mathematical framework for assessing the reliability of lithium-ion battery systems of urban electric transport rolling stock, taking into account selectively placed thermal barriers, was developed. The reliability problem was formulated in the context of cascading failures initiated by thermal instability of individual cells and was described using coupled partial differential equations of heat transfer and Arrhenius-type temperature-dependent degradation kinetics. A deterministic finite element model was constructed to evaluate the influence of different thermal barrier configurations on temperature fields and the state of health (SoH) degradation rate. The model was further extended using Monte Carlo simulation to incorporate uncertainty in key parameters and to estimate confidence intervals of reliability indicators. In addition, a discrete optimization problem of barrier placement was formulated and solved using a genetic algorithm. It was demonstrated that selective placement of thermal barriers in thermally critical regions led to a reduction in degradation rate by 15%–20% compared to both barrier-free and uniformly shielded configurations, while also reducing uncertainty in lifetime prediction. The obtained results provided a quantitative basis for reliability-oriented design and optimization of battery systems.