Simplified Battery Pack Modeling Considering Inconsistency and Evolution of Current Distribution

Abstract

With the development of battery technology, large-scale battery applications are increasing. In order to obtain a higher current and voltage level and improve the overall energy efficiency, batteries are connected in series and parallel. Bulk model is the most used model to simulate battery packs, and the simulation results of single cell are enlarged several times to represent a battery pack. But bulk model ignores inconsistency between the batteries, and when the current magnification is large, such as in the extreme fast charge scenario, this neglect cannot reflect the current distribution inside the battery pack. Our paper proposes a simplify algorithm based on equivalent circuit model, which applied for non-uniform series and parallel-connected batteries. This simplification can greatly improve simulation speed while maintaining accuracy under the consideration of inconsistency. More importantly, this algorithm applies to any complex circuit, regardless of how many series-parallel structure layers. With the proposed algorithm, Monte Carlo simulations were evaluated to obtain the influence of battery series and parallel number and normal distribution parameters on current distribution. Simulation results show that an increase in the number of series will reduce the inconsistency of the current distribution, and an increase in the number of parallel and an increase in the relative standard deviation of the normal distribution of the battery parameters will increase the inconsistency of the current distribution.