66 September/October 2025 | E-Mobility Engineering The energy overhead of thermal management systems represents a significant design consideration, with typical consumption ranging from 0.5% to 10% of the total battery energy depending on system type and operating conditions. Liquid-cooled systems generally achieve the lowest parasitic losses, with welldesigned implementations consuming less than 0.5% of energy throughput for pumping power alone. Air-cooled systems, while simpler in concept, typically require several percent of the total energy owing to air’s low heat capacity and the high volumetric flow rates needed for effective cooling. Several factors influence overall energy consumption. Pressure drop in liquid systems dominates pumping power requirements, driving innovation in low-loss channel geometries and hydraulic optimisation. Fluid selection also plays a role, with low-viscosity dielectric fluids gaining favour for their ability to reduce pumping losses while maintaining excellent thermal performance. At the system level, variable-speed pumps and smart control strategies that match cooling capacity to immediate thermal loads can reduce energy consumption by 15– 25% compared with fixed-flow designs. Extreme conditions present additional challenges. Fast charging in hot climates may temporarily increase cooling energy demands beyond 10% of pack capacity when active refrigeration is required. Cold weather operation introduces complementary challenges, with battery heating requirements sometimes exceeding cooling loads. These scenarios have spurred development of integrated thermal management systems that share resources between battery cooling and vehicle HVAC systems, as well as increased use of passive thermal storage elements to smooth peak demands. The field continues to evolve rapidly in response to three competing imperatives: handling increasing heat fluxes from 3C+ charging, minimising parasitic losses to meet efficiency targets, and maintaining safety margins throughout cell lifespan. Recent innovations include novel dielectric fluid formulations that optimise the balance between thermal performance and electrical safety, along with additivemanufactured cooling structures featuring optimised flow paths impossible to produce with conventional methods. Digital twin approaches are gaining traction for their ability to support real-time thermal optimisation, while advanced control algorithms increasingly incorporate predictive capabilities that anticipate thermal transients rather than simply reacting to them. Extreme cases Designing thermal management systems that perform reliably across temperature extremes ranging from -30 to +50 C requires addressing fundamentally different challenges at each end of the spectrum. In cold climates, the primary obstacle involves maintaining cell temperatures above critical thresholds that enable charging and discharge. Modern systems employ several strategies to combat sub-zero conditions, beginning with preconditioning protocols that heat batteries before charging commences. Lack of adequate pre-heating can double charging times, so optimising the process is crucial. The thermal path from heat source to battery cells presents multiple barriers in conventional systems. Traditional water–glycol cooling architectures require heat to traverse several interfaces: throughout the body of the cell, across thermal interface materials and through the cooling plate. This tortuous path reduces efficiency and slows response times. Dielectric fluids in immersion cooling systems offer distinct advantages here, providing direct omnidirectional heat transfer to cell surfaces while requiring less energy to raise fluid temperatures compared with waterglycol mixtures owing to their lower specific heat capacity. At the opposite extreme, high ambient temperatures demand robust cooling capacity to handle peak heat loads in 50+ C environments. System designers employ various techniques including two-phase cooling with refrigerants, radiative heat shields to reduce ambient heat ingress and advanced control algorithms that dynamically adjust cooling parameters. Material selection becomes critical at both extremes – polymers for seals and gaskets must maintain mechanical properties across the full temperature range, while metals in cold plates require careful thermal stress analysis to prevent fatigue failure during repeated cycling. Product focus | Battery cooling Cold plates must be compatible with a wide range of fluids, from water–glycol mixtures to dielectric fluids to ensure corrosion resistance and pressure containment etc. (Image courtesy of Baknor)
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