Impact of Thermal Imbalances on Energy Availability, State of Power, and aging in Immersion-Cooled Batteries

This study investigates the impact of thermal imbalances on energy delivery and Battery State of Power (SoP) in immersion-cooled battery cells. It explores how these imbalances, which arise when cells within a module operate at different temperatures, lead to variations in internal resistance and inefficiencies in energy storage and discharge. Such imbalances critically affect the battery's SoP, representing the maximum charge or discharge power the system can support over specific time intervals. By analyzing SoP over 2-second and 10-second durations, we assess how thermal imbalances influence both short-term and medium-term power capabilities. Temperature significantly impacts cell aging, and imbalances can accelerate degradation in some cells, ultimately affecting serviceability. To address these issues, we employ a high-level simulation framework that integrates advanced tools. GT-SUITE software optimizes thermal performance by adjusting coolant temperature and flow rate to manage thermal imbalances. Concurrently, Ansys software provides detailed thermal simulations, considering heat generation within cells and coolant dynamics. This integration uses a Functional Mock-up Unit (FMU) approach. A MATLAB/SIMULINK controller implements a degradation method, while an electrochemical model illustrates the effects of thermal imbalance on aging. Additionally, we introduce an electrical State of Charge (SOC)-based balancing method to dynamically redistribute electrical loads among cells, correcting imbalances in energy storage and discharge. This strategy aims to enhance energy distribution, improve SoP, reduce aging, and minimize internal resistance differences. The effectiveness of this comprehensive approach will be evaluated based on its impact on energy delivery efficiency, SoP stability over 2-second and 10-second intervals, and the overall lifespan of the battery module, ultimately optimizing cooling parameters and enhancing performance and longevity.