A Novel Lithium-ion Battery Pack Modeling Framework - Series-Connected Case Study

In this paper, a novel physics-based modeling framework is developed for lithium ion battery packs. To address a gap in the literature for pack-level simulation, we establish a high fidelity physics-based model that incorporates electrochemical-thermal-aging behavior for each cell and which is then upscaled at the pack level by incorporating electrical and thermal interaction terms. Such a construct is suitable both for performance analysis upon cell heterogeneity as well as control and optimization for on-board operation. Governing equations in the form of Partial Differential Equations (PDEs) are discretized into a system of Ordinary Differential Equations (ODEs) using Finite Difference and Finite Volume methods and reformulated into state-space models for both cell and pack dynamics. Computational time studies are conducted to demonstrate the effects of spatial discretization fidelity and pack size on simulation time. Pack model predictive capabilities are exercised by inducing hetereogeinity in the cell design parameters and effects of parameter perturbation are shown for pack voltage and energy responses. The goal for this modeling framework is to provide a computationally-feasible and easily scalable platform for high-fidelity offline simulation and optimization without compromising the integrity of cell dynamics across multiple time scales.