Cell-to-cell manufacturing variability analysis in liquid-cooled module battery pack for automotive transportation

In electric vehicles, production inconsistencies in battery cells impair pack efficiency and exacerbate imbalanced operating conditions. While the existing literature primarily focuses on the impact of cell characteristics, such as capacity and internal resistance, on electrical behaviour, research into the underlying physical sources of this variability remains limited. In this context, this paper analyses the impact of cell-to-cell manufacturing variability on the current and temperature distribution within an automotive battery module. The novelty of this investigation lies in correlating specific cell-component variations with their aggregate effects on module-level performance. In the first part of the manuscript, a Variation Mode and Effect Analysis is conducted to identify and quantify the most significant manufacturing variations at both the cell and module levels. Subsequently, an electro-thermal lumped-parameter model is developed and validated to assess the influence of these inconsistencies on a commercial battery pack through a Sensitivity Analysis. The results indicate that battery mass, surface area, welding resistance, and cooling plate diameter are the primary drivers of current imbalance and non-uniform temperature distribution. Furthermore, uncertainty propagation analysis reveals a tendency toward over-discharging and overheating in cells affected by these production variations. Specifically, fluctuations in mass and welding resistance significantly impact electrical behaviour, inducing maximum variations in current and State of Charge of approximately 2%. Meanwhile, variations in mass, surface area, and cooling plate diameter result in a temperature gradient up to 5% within the module. These findings provide valuable insights for electric vehicle manufacturers, emphasizing the necessity of accounting for manufacturing variability during the battery pack design phase.