ChaoJi Charging Connector Thermal Performance Unveiled in New Study
The future of electric vehicle (EV) charging is rapidly evolving, driven by consumer demand for faster, more reliable, and universally compatible solutions. As the global automotive industry accelerates its shift toward electrification, the limitations of current charging infrastructure—particularly long charging times and fragmented standards—have emerged as critical barriers to mass adoption. In response, next-generation high-power charging technologies are being developed to address these challenges, with ChaoJi charging standing at the forefront of this transformation. A recent in-depth study published in Guangdong Electric Power has now provided crucial insights into one of the most pressing engineering challenges associated with ultra-fast charging: thermal management in high-current connectors.
The research, conducted by a team of engineers from Nari Technology Co., Ltd. and State Grid Shanghai Electric Power Company, focuses on the thermal behavior of the ChaoJi charging connector under extreme operating conditions. With charging currents projected to reach up to 800 amperes and voltages exceeding 1500 volts, managing heat generation within the connector is paramount to ensuring safety, longevity, and performance. The study presents a comprehensive thermal simulation model that not only advances the theoretical understanding of connector thermodynamics but also offers practical guidance for the design and optimization of future EV charging systems.
As EVs become more powerful and battery capacities increase, the need for rapid charging grows ever more urgent. Consumers expect charging experiences comparable to refueling a conventional vehicle, which necessitates power delivery in the megawatt range. The ChaoJi charging standard, developed with the goal of unifying global charging protocols, is designed to support such high-power applications. Unlike earlier standards that were region-specific or limited in power output, ChaoJi aims to provide a scalable, interoperable, and safe solution for both current and next-generation electric vehicles. However, delivering such high power levels introduces significant engineering challenges, chief among them being the management of resistive heating within the charging interface.
When high currents pass through electrical conductors, energy is lost in the form of heat due to the inherent resistance of the materials involved. In a charging connector, this heating occurs primarily at two locations: within the bulk of the conductor and at the contact interface between the plug and the socket. While the former is relatively straightforward to model, the latter is far more complex due to the microscopic nature of the contact points and the influence of surface conditions, oxidation, and mechanical pressure. If not properly managed, excessive heat can degrade the connector’s materials, increase contact resistance over time, and potentially lead to failure or safety hazards.
The research team, led by Li Yijie of Nari Technology, approached this challenge through a combination of theoretical modeling and advanced computational simulation. Recognizing the complexity of real-world connector geometries, they began by simplifying the physical structure of the ChaoJi connector’s contact elements into cylindrical models. This simplification allowed them to isolate and analyze the key variables influencing thermal performance without being overwhelmed by geometric intricacies. The contact components, typically made of high-conductivity metals such as copper alloys, were modeled as cylindrical conductors with defined electrical and thermal properties.
A critical aspect of their analysis was the distinction between bulk resistance and contact resistance. Bulk resistance, which depends on the material’s resistivity, length, and cross-sectional area, contributes to uniform heating along the conductor. Contact resistance, however, arises at the interface where two conductive surfaces meet. This resistance is influenced by several factors, including the actual contact area, surface roughness, oxidation layers, and the mechanical force pressing the surfaces together. The study highlights that even small increases in contact resistance can lead to disproportionate temperature rises due to the quadratic relationship between current and resistive heating (I²R losses).
To model the thermal behavior of the connector, the researchers employed a thermal resistance network approach, a method commonly used in electronics cooling and heat transfer analysis. In this approach, the flow of heat from the internal contact points to the external environment is represented as an electrical circuit, where temperature differences correspond to voltage drops and heat flow corresponds to current. Thermal resistances—such as those associated with conduction through insulation, convection to ambient air, and radiative heat loss—are treated as circuit elements. This analogy allows engineers to apply familiar circuit analysis techniques to predict temperature distributions within the system.
The thermal circuit model included multiple pathways for heat dissipation. Heat generated at the contact interface first conducts through the connector’s internal materials, including any insulating layers and the metallic housing. From there, it is transferred to the surrounding air through natural convection and thermal radiation. The effectiveness of this heat transfer depends on several factors, including the surface area of the housing, the emissivity of the material, and the ambient airflow conditions. The study assumed natural convection, which is typical for stationary charging scenarios, and used standard values for convective heat transfer coefficients and surface emissivity.
One of the most significant findings of the research was the confirmation of a quadratic relationship between the charging current and the resulting temperature rise in the connector. As the current increases, the power dissipated as heat increases with the square of the current, leading to a rapid escalation in temperature. This means that doubling the charging current results in a fourfold increase in heat generation, placing exponentially greater demands on the thermal management system. The simulation results clearly demonstrated this trend, showing that both the minimum and maximum temperatures within the connector increased in proportion to the square of the applied current.
This finding has profound implications for the design of high-power charging systems. It underscores the need for robust thermal management strategies, especially as the industry moves toward even higher current levels. Passive cooling methods, such as heat sinks and thermally conductive materials, may be sufficient for moderate power levels, but active cooling—such as forced air or liquid cooling—may become necessary for sustained ultra-fast charging. The study’s model provides a valuable tool for evaluating the effectiveness of different cooling approaches and optimizing connector design before physical prototypes are built.
The simulations were performed using FloTHERM 2021, a widely used computational fluid dynamics (CFD) software package for thermal analysis in electronics and electrical systems. The software allowed the researchers to create a detailed 3D model of the ChaoJi connector, assign material properties, define boundary conditions, and simulate the thermal response under various operating scenarios. The computational setup included realistic parameters such as an ambient temperature of 25°C, a maximum current of 800 A, and a contact resistance of 100 microohms—values representative of actual high-power charging applications.
The simulation results revealed a clear thermal gradient within the connector. The highest temperatures were observed near the contact interface, particularly around the pin and socket areas where current density is greatest. From there, the temperature decreased radially outward toward the outer housing, which acted as a heat sink and facilitated heat dissipation to the environment. This spatial distribution of temperature is consistent with theoretical expectations and confirms that the contact region is the most thermally stressed part of the connector.
An important practical outcome of the study was the validation of the ChaoJi connector’s ability to operate safely within specified thermal limits. Under the simulated conditions, the connector’s temperature rise remained below 65 K when subjected to a current of 800 A, meeting industry standards for thermal performance. This demonstrates that the current design, when combined with appropriate materials and cooling strategies, is capable of supporting the high-power charging demands of next-generation EVs. However, the study also cautions that prolonged operation at maximum current levels could lead to cumulative thermal stress, potentially accelerating material degradation and reducing the connector’s service life.
The research also contributes to the broader understanding of contact physics in high-current electrical systems. The model accounts for both constriction resistance—the resistance caused by the limited actual contact area between two surfaces—and film resistance, which arises from thin layers of oxide or contamination on the metal surfaces. These factors are often overlooked in simplified analyses but play a critical role in real-world performance. By incorporating them into the thermal model, the researchers provide a more accurate and comprehensive picture of the connector’s behavior.
From a design perspective, the study offers several actionable insights. First, it emphasizes the importance of maximizing contact area and ensuring consistent mechanical pressure to minimize contact resistance. This can be achieved through precision engineering of the contact geometry and the use of spring-loaded or compliant contact elements. Second, it highlights the value of materials with high thermal conductivity, such as copper or aluminum alloys, to facilitate rapid heat transfer away from the contact zone. Third, it underscores the need for effective external cooling, whether through increased surface area, improved airflow, or active cooling systems.
The implications of this research extend beyond the immediate application to ChaoJi connectors. As the automotive industry continues to push the boundaries of charging speed and power, the principles and methodologies developed in this study can be applied to other high-current electrical systems, including battery terminals, power distribution units, and onboard chargers. The ability to accurately predict and manage thermal performance is essential for ensuring the reliability and safety of all high-power electrical components in electric vehicles.
Moreover, the work addresses a notable gap in the existing literature. While there has been considerable research on general electrical connectors and their thermal behavior, specific studies on the ChaoJi standard have been limited. This paper fills that void by providing a detailed, physics-based analysis tailored to the unique requirements of the ChaoJi interface. It serves as a foundational reference for engineers and researchers working on next-generation charging technologies.
The study also has important implications for standardization and regulatory bodies. As new charging standards are developed and adopted, thermal performance criteria must be established to ensure interoperability and safety across different manufacturers and regions. The models and findings presented in this research can inform the development of such standards, providing a scientific basis for setting acceptable temperature rise limits and testing procedures.
In addition to its technical contributions, the research exemplifies the collaborative nature of innovation in the EV ecosystem. The partnership between Nari Technology, a leading provider of smart grid solutions, and State Grid Shanghai Electric Power Company, a major utility operator, reflects the integration of expertise across the energy and transportation sectors. Such collaborations are essential for addressing the systemic challenges of electrification, from grid integration to end-user charging experiences.
Looking ahead, the findings of this study will likely influence the next phase of ChaoJi connector development. Future work may focus on optimizing the connector’s geometry for better heat dissipation, exploring advanced materials with superior thermal and electrical properties, or integrating real-time temperature monitoring and adaptive control systems. The ultimate goal is to create a charging interface that is not only fast and powerful but also durable, safe, and user-friendly.
As the world moves closer to a zero-emission transportation future, the role of high-power charging infrastructure cannot be overstated. Technologies like ChaoJi represent a critical enabler of this transition, removing one of the last major obstacles to EV adoption: range and charging anxiety. By providing a deeper understanding of the thermal dynamics within these systems, this research helps pave the way for a more efficient, reliable, and sustainable electric mobility ecosystem.
The work by Li Yijie, Lu Xiaorong, Wu Dan, Lei Ting, and Zhang Kaiyu from Nari Technology Co., Ltd. and State Grid Shanghai Electric Power Company, published in Guangdong Electric Power, DOI: 10.3969/j.issn.1007-290X.2024.04.004, stands as a significant contribution to the field of electric vehicle charging technology. It combines rigorous scientific analysis with practical engineering insights, offering a roadmap for the development of next-generation charging solutions that are both powerful and safe.