A high-power dc fast-charging station equipped with liquid-cooled charging cables designed to support sustained currents above 350 A for rapid energy transfer.
Electric-vehicle (EV) connectors and charging cables must safely handle increasingly high currents and power levels. Conventional air-cooled cables and connectors begin to reach practical limits around 250 A continuous, with some designs capable of short bursts near 300 A before heat buildup, weight, and stiffness become significant concerns.
However, many new dc fast chargers exceed these levels, pushing toward 350 to 500 A to deliver higher charging power. This shift is driving renewed focus on liquid-cooled systems that can dissipate more heat, maintain smaller cable diameters, and sustain high-current operation without overheating.
How liquid-cooled systems differ
At high currents, resistive heating in cable conductors and connector contacts becomes a significant concern. The connector must manage the electrical connection and safely dissipate heat while maintaining insulation and operator-safety requirements. As charging power increases beyond 300 kW in dc fast-charging applications, typical air-cooled systems require thicker cables and larger airflow paths or forced-air cooling. This adds cost, weight, and packaging complexity.
Liquid-cooled charging systems offer an alternative. In these systems, the conductor or connector body incorporates embedded channels or an external jacket through which coolant flows. The coolant, typically a water-glycol mixture, dielectric oil, or other compatible fluid, absorbs heat from the conductor and transfers it to a heat exchanger.
This approach provides a direct and highly efficient thermal path from the heat source to the coolant, lowering the overall thermal resistance of the system. Effective liquid circulation prevents localized hot spots that can accelerate conductor oxidation or contact wear. As the fluid moves, thermal resistance between conductor and ambient is reduced compared with air cooling.
A liquid-cooled CCS-type connector design concept similar to what’s used in current 475-kW ultra-fast dc chargers. (Image: Gilbarco Veeder-Root)
This allows smaller cable diameters, prevents overheating, and maintains ergonomic handling during high-power charging.
From a design perspective, lighter, thinner cables improve user experience and reduce load on cable-management systems. In fact, one recent market report from Introspective Market Research finds that liquid cooling “allows the charging cables to be lighter and thinner, reducing their weight by approximately 40%.”
What’s more, the smaller, lighter cables improve ergonomics and reduce strain for users, while simplifying the integration of automated charging systems.
Engineering trade-offs and system considerations
Adopting liquid-cooled connectors is more complicated than simply switching designs. Engineers must address:
- Coolant selection and insulation: The coolant must not degrade insulation or react with contact materials while withstanding thermal cycling and voltage stress.
- Sealing and leakage risk: The presence of fluid paths increases the importance of reliable seals and leak detection.
- Thermal interface design: The path from conductor to coolant must minimize thermal resistance. A structural study of liquid-cooled cable cores highlights how cable geometry directly impacts cooling efficiency. (ScienceDirect)
- Connector durability: Mating cycles, vibration, and temperature changes must not compromise seals or electrical performance.
- Cost and compatibility: Additional cooling components and infrastructure can increase cost and limit interoperability with existing charging networks.
The shift to liquid-cooled systems
The move toward liquid-cooled charging systems is driven by a need for sustained high-current operation, improved efficiency, and greater reliability. Active cooling allows fast chargers to deliver high energy levels in shorter times without overheating or derating. By keeping cable cross-sections manageable, liquid cooling enables sustained charging currents above 500 A without overheating.
Phoenix Contact 500 A liquid-cooled charging cable assembly showing integrated temperature sensors within the power contacts for precise thermal monitoring during high-current dc fast charging. (Image: Mouser)
In systems without sufficient cooling, connectors can enter a protective derating mode, often called thermal throttling, where charging current is automatically reduced to prevent temperature rise beyond safe limits. Liquid cooling mitigates this behavior by maintaining stable thermal conditions, ensuring the charger operates at full rated output for longer durations. The result is more consistent station uptime and predictable performance under continuous heavy use.
Additionally, it’s important to keep up with demands.
“Charging speeds are increasing, necessitating connectors capable of handling significantly larger currents and heat dissipation,” according to Market Report Analytics. “This trend pushes the development of liquid-cooled systems that can safely and efficiently manage these high power demands. Simultaneously, the growing need for interoperability among different charging networks and vehicles is leading to efforts towards standardization.”
Liquid-cooled charging technology is advancing in step with evolving global standards such as IEC 62196, UL 2251, and ISO 17409, which govern insulation, touch-temperature limits, and safety during high-voltage charging. These standards also define testing criteria for coolant containment, dielectric integrity, and post-failure discharge to ensure user protection in fault scenarios.
Standardization ensures consistent performance across regions and enables compatibility between different charging networks and vehicle platforms.
Conclusion
For engineers designing high-power charging systems, liquid-cooled connectors offer a practical solution to the thermal and mechanical limits of conventional air-cooled designs. While these systems add complexity and cost, they enable faster charging, lighter cables, and improved operational stability.
As current levels climb into the hundreds of amps and beyond, liquid cooling is emerging as a key enabling technology in advanced EV charging infrastructure. Market data reflects the trend. The global liquid-cooled fast-charging cable market is projected to reach USD 7.86 billion by 2033, growing at a CAGR of 20.8%, according to research firm, DataIntelo.
“As battery capacities and charging rates for EVs continue to rise, there is a pressing need for charging cables that can efficiently handle higher currents without overheating or compromising safety,” their report states. “Liquid-cooled fast-charging cables are uniquely positioned to meet this demand, as they leverage advanced thermal management systems to dissipate heat effectively, enabling ultra-fast charging speeds that are essential for both passenger and commercial EVs.”
References
- “Electric Vehicle Liquid-Cooled Charging Connector Market Report 2024–2033,” Market Report Analytics.
- “Liquid-Cooled Charging Station for Electric Vehicle Market,” Introspective Market Research.
- “Liquid-Cooled Fast-Charging Cable Market Report,” DataIntelo.
- “Liquid-Cooled Charging Cables: The Future of Fast, Safe, and Efficient EV Charging,” Joint Charging.
- “Experimental Study on Liquid-Cooled Cable Core Structures for High-Power Electric-Vehicle Charging,” Applied Thermal Engineering, ScienceDirect.
- IEC 62196: Plugs, Socket-Outlets, Vehicle Connectors, and Vehicle Inlets – Conductive Charging of Electric Vehicles, International Electrotechnical Commission, Geneva.
- UL 2251: Plugs, Receptacles, and Couplers for Electric Vehicles, Underwriters Laboratories, Northbrook, Illinois.
- ISO 17409: Electrically Propelled Road Vehicles – Conductive Power Transfer – Safety Requirements, International Organization for Standardization, Geneva.
Filed Under: Charging, FAQs