EV Battery Cooling Technologies: Fundamentals of Battery Thermal Management
EV Battery Cooling Technologies: The “Thermal Code” Safeguarding the Power Core
In new energy vehicles, lithium-ion batteries are the core of the powertrain. Their performance, safety, and service life are highly dependent on operating temperature. Excessively high or low temperatures can lead to capacity degradation, increased internal resistance, and even serious safety risks.
As a result, the Battery Thermal Management System (BTMS) has become a critical element in EV system design, with cooling strategies playing a decisive role in vehicle reliability and energy efficiency.
1. Impact of Temperature on Lithium-Ion Battery Performance and Lifetime
Lithium-ion batteries offer high energy density and operating voltage but are particularly sensitive to temperature variations. Engineering practice and experimental studies indicate that:
High temperatures accelerate internal side reactions, causing electrolyte decomposition, SEI layer degradation, and active material loss. This leads to capacity fade and increased internal resistance. Under sustained thermal stress or insufficient heat dissipation, the risk of thermal runaway rises significantly.
Low temperatures reduce ion mobility, resulting in lower charge/discharge efficiency and increased lithium plating risk under improper charging conditions, negatively affecting cycle life and safety.
Industry experience suggests that the optimal operating temperature range for lithium-ion batteries is typically 25–40 °C, where capacity retention, power output, and lifespan reach a balanced optimum. With increasing power density and fast-charging demands, heat generation under high-current conditions has risen sharply, placing greater demands on cooling system performance.
2. Mainstream Battery Cooling Technologies and Engineering Characteristics
Current EV battery cooling solutions primarily include air cooling, liquid cooling, heat pipe cooling, and phase change material (PCM) cooling. Each approach differs in heat dissipation capability, system complexity, and application suitability.
2.1 Air Cooling: Simple Structure for Low to Medium Thermal Loads
Air cooling removes heat through convection, either via natural or forced airflow. Its advantages include simple structure, low cost, and ease of maintenance, making it suitable for battery systems with lower power density or strong cost constraints.
However, due to air’s low thermal conductivity and heat capacity, air cooling offers limited performance under high C-rates or high ambient temperatures. Achieving uniform temperature distribution within battery modules is also challenging. Future improvements will rely on optimized airflow design and module layout.
2.2 Liquid Cooling: The Mainstream Solution for High-Energy-Density Batteries
Liquid cooling utilizes the high specific heat capacity and thermal conductivity of coolants to extract heat through cooling plates or channels. It is currently the dominant solution for passenger EVs and high-power battery packs.
Liquid cooling systems can be classified into direct and indirect contact types, with indirect liquid cooling being more widely adopted due to higher safety and reliability. Compared with air cooling, liquid cooling offers superior temperature control accuracy and uniformity, albeit at the cost of increased system complexity, weight, and sealing requirements. Key design priorities include flow channel optimization, sealing reliability, and energy consumption control.
2.3 Heat Pipe Cooling: Localized High-Efficiency Heat Transfer
Heat pipes transfer heat efficiently through phase-change mechanisms, featuring low thermal resistance and fast response. In battery systems, heat pipes are typically used as auxiliary solutions to address localized hotspots, often in combination with liquid or air cooling.
Their application is constrained by packaging space, contact area, and manufacturing complexity. Heat pipe cooling is best suited for compact systems with high local heat flux. Future development trends focus on miniaturization and modular integration.
2.4 Phase Change Material (PCM) Cooling: Passive Peak Heat Absorption
PCM cooling absorbs heat through phase transitions, effectively suppressing temperature fluctuations without additional energy consumption. Its primary function is peak shaving during short-term high heat loads.
Due to the inherently low thermal conductivity of most PCMs, standalone PCM solutions are insufficient for sustained high-power operation. In practice, PCMs are typically combined with liquid or air cooling systems. Enhancing PCM thermal conductivity and system-level integration remains key to broader adoption.
3. Technology Trends: Synergy and System-Level Optimization
As battery systems evolve toward higher energy density and higher charge/discharge rates, no single cooling technology can meet all requirements. Future battery cooling systems will increasingly emphasize hybrid and collaborative approaches:
Air cooling: Extended applicability through structural and flow optimization
Liquid cooling: Higher integration, lower energy consumption, and enhanced reliability
Heat pipes and PCM: Localized enhancement and thermal buffering, working in coordination with primary cooling systems
The ultimate goal is to balance temperature control precision, system efficiency, and structural compactness.
RHI Busbars: Thermal-Optimized Battery Connections
Within battery thermal management systems, busbars not only serve as electrical conductors but also act as important internal heat transfer paths. Material selection, structural design, and insulation methods directly influence heat distribution and cooling efficiency.
Leveraging extensive experience in copper and aluminum busbar manufacturing, RHI provides engineering-ready busbar solutions tailored to different battery cooling technologies.
1. Busbar Design for Thermoelectric and Localized Cooling
For localized temperature control or thermoelectric cooling scenarios, RHI applies precision machining and customized structures to ensure stable contact between busbars and cooling components. This reduces thermal contact resistance and supports temperature sensor integration for real-time monitoring and control.
2. Structural Adaptation for Heat Pipe Cooling
RHI busbars can be locally optimized around heat pipe evaporator zones to efficiently transfer heat into the heat pipe system. Optimized bending radii and complex geometries enhance packaging flexibility in compact battery packs.
3. Universal Solutions for Liquid, Air, and PCM Cooling Systems
Liquid cooling: Optimized contact interfaces between busbars and cooling plates improve heat transfer efficiency, supported by mature insulation and sealing processes for enhanced reliability.
Air cooling: Surface treatments and structural optimization improve convective and radiative heat dissipation.
PCM systems: Surface roughening and corrosion-resistant treatments enhance long-term interface stability between busbars and phase change materials.
Manufacturing Capability Drives Thermal Reliability
RHI specializes in the design and manufacturing of copper and aluminum busbars and battery connection solutions, including rigid busbars, flexible connectors, copper-aluminum busbars, high-temperature insulated busbars, and PI-insulated rigid busbars. Integrated support is provided across material selection, structural design, and insulation processes to match diverse battery thermal management architectures.
In new energy vehicles and energy storage systems, busbars are not merely electrical components—they are integral elements of the thermal management system. RHI delivers safer, more reliable battery systems through deep industry expertise and manufacturing excellence. We provide customized busbar solutions—reach out to engineer your success.