Efficient physics-based modeling and experimental validation of parallel-connected battery cells enabled by the transmission line model

Abstract

Battery modules composed of parallel-connected cells are commonly used as building blocks of battery packs, but their behavior is complex due to cell dynamics, as well as cell-to-cell heterogeneities and interactions. Furthermore, their simulation by means of empirical equivalent circuit models poses limitations because of lack of generalization, whereas electrochemical models lead to a challenging calculation of the current distribution. In this article, an electrically consistent method for the calculation of the equivalent voltage and resistance of a cell is presented according to the physically motivated discrete transmission line model. This enables the efficient computation of output voltage and current distribution for parallel-connected cells while providing interpretable physical information about the operation at each level. The presented approach is validated experimentally against a dataset of a 4P module in which interconnection resistance, ambient temperature, and the presence of an aged cell are considered as input parameters, with accurate and consistent results for module voltage (≤20 mV RMS) and current distribution (≤4.4% RMS). Moreover, the proposed framework exhibits higher computational efficiency and comparable scalability in relation to established approaches, while providing improved consistency between module-level behavior and cell-level dynamics. Therefore, the proposed method based on the transmission line model and hierarchical simplification is a suitable alternative for the physically motivated simulation and analysis of battery modules.