65 E-Mobility Engineering | September/October 2025 Battery cooling | Product focus with high precision. Validation remains essential, with calorimeter testing and infrared thermography used to verify simulation results within 5% error margins. The most advanced workflows now integrate 1D system models of pumps, radiators and HVAC loops with detailed 3D computational fluid dynamics models of systems where the detailed geometry is of specific interest. This combined approach captures not just cell-level heating but also secondary effects such as busbar temperature rise and transient thermal inertia. The computational demands are substantial, driving adoption of GPU-accelerated solvers that provide order-ofmagnitude speed improvements over traditional CPU-based systems. Uniformity and efficiency Maintaining tight temperature uniformity across cells has emerged as one of the most demanding aspects of battery thermal management. Modern systems target ±2–3 C differentials, a significant tightening from the ±10 C tolerances common just a few years ago. This challenge is compounded by fundamental material characteristics – most cell designs exhibit anisotropic thermal conductivity, with cylindrical cells conducting heat more than an order of magnitude more effectively along their axis than radially. These material properties create significant and complex thermal gradients if not properly managed. Conventional bottom-cooling approaches can inadvertently worsen temperature differentials in cylindrical cell stacks by effectively cooling only one end while heat accumulates at the opposite pole. This has driven development of more sophisticated cooling strategies that account for directional heat transfer characteristics. Consequently, immersion cooling has gained attention for its ability to provide omnidirectional heat extraction, while advanced cold plate designs incorporate microchannels and tailored flow distribution to maintain uniform interface temperatures. Flow path optimisation plays a critical role in achieving temperature uniformity. U-flow configurations with parallel cooling channels, combined with precisely calibrated hydraulic restrictors, help balance mass flow distribution across complex pack geometries. Counter-flow designs minimise outlet temperature rise, while conformable cooling ribbons maintain consistent thermal contact across cell surfaces. These mechanical solutions are increasingly paired with intelligent control systems incorporating realtime thermal sensors and adaptive algorithms that dynamically adjust cooling parameters in response to actual operating conditions. Immersion cooling using dielectric oils provides superior thermal performance by enabling direct contact with battery cells. This approach can simplify pack design by eliminating the need for separate cooling plates or channels. While the higher cost and integration challenges have so far limited its adoption to high-performance or specialised applications, this could soon change. Two-phase cooling systems using refrigerants offer rapid heat extraction, making them ideal for fast charging. However, they are more complex, requiring additional components like condensers and evaporators. Additionally, flammability concerns and regulatory restrictions on certain refrigerants further complicate their use. Calculating heat flux Determining the maximum heat flux a cooling system must handle begins with understanding cell behaviour under extreme conditions. Fast-charging events typically represent the most thermally demanding scenarios, requiring systems to dissipate substantial heat loads while maintaining safe cell operating temperatures. Engineers employ multiscale modelling approaches, starting with electrochemical analysis of individual cells and scaling up to full pack simulations. Modern thermal analysis combines several critical methodologies. Electrochemical-thermal models quantify heat generation from multiple sources including Joule heating and entropy changes during charge/discharge cycles. These models account for how internal resistance varies with both state of charge and temperature – a crucial factor because resistance decreases as the battery heats up (while electrical resistance in busbars and connectors increases with temperature), but the temperature must remain below the thresholds that accelerate degradation. Conjugate heat transfer analysis is used in the modelling of the complex interaction between solid components and cooling fluids, predicting interface heat fluxes Betamate TC thermal conductive adhesives are used for cell-to-cell bonding and other applications for battery pack assembly (Image courtesy of DuPont)
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