57 Megawatt charging | Deep insight E-Mobility Engineering | May/June 2025 Cooling Charging at such high levels of power generates substantial heat. To keep cables lightweight and flexible, less copper is often used, which increases electrical resistance. When high currents flow through these resistive components, a significant amount of heat is produced. This excess heat can damage components, reduce efficiency and pose safety risks. Consequently, effective cooling technologies are essential for maintaining the durability and performance of a charging system. As current levels rise, advanced cooling systems become essential for effective design, says Mathieu Chaligne, project and product manager, charging systems at connector developer Stäubli. When choosing a cooling technology, two main factors must be considered: the cooling medium and the cable technology. Water–glycol mixtures are commonly used in EV systems because of their efficient heat exchange and environmental safety. Oil-based coolants, while effective in state-ofthe-art high-voltage static applications, require more complex infrastructure for maintenance and disposal. Stäubli favours water-based solutions for their ease of handling and overall efficiency. The choice between direct and indirect cooling also impacts on both performance and cost. In direct-cooled cables, the cooling fluid directly contacts the cable conductor, allowing for efficient heat exchange. This reduces the amount of copper needed and results in thinner, lighter cables. However, the fluid cools the cable conductor through an isolated tube and is never in direct contact with the copper. For indirect cooling, the cables are cooled via an external heat exchanger. While the cables tend to be heavier, this method generates less heat, thereby allowing smaller coolers to provide the necessary cooling – ultimately reducing both operational and capital costs. Indirect cooling is generally the more cost-effective approach because it consumes less energy and requires less cooling power. Extensive testing to develop cooling solutions that balance performance and cost mean Stäubli is open to using both direct and indirect cooling systems with water–glycol fluid for the MCS connector. Both technologies provide reliable performance and can be tailored to meet various system requirements. The connectors, scheduled for release in parts in mid-2025, are designed to be scalable and adaptable, ensuring compatibility with both current and future MCS infrastructure. Thermal compatibility The connectors also need to work with the inlets, and these have been tested at the NREL using a thermal interoperability test bench. The connector, consisting of a cable approximately 2 m in length provided by the participant and terminated at one end with an MCS connector with SAE J3271 standard is a TIR, none of the prototype MCS stations are compliant but they do constitute part of the validation process during development. An early MCS–NACS dual-output functional prototype was unveiled in October 2023, with a 1800 A liquidcooled Rema MCS charging cable. Eight MCS charging cable and inlet manufacturers are planning to participate in coordinated communication interoperability testing of couplers and inlets at the Argonne National Laboratory. Three iterations of the CharIN MCS task group coupler design (V1, V2, and V3) led to the final v3.2 design described in the SAE J3271 standard. Three rounds of testing were conducted at the US National Renewable Energy Laboratory (NREL) with prototype and pre-production test articles, up to 3000 A, including elevated ambient test conditions. There are three charging configurations indicating charging power capability: • Configuration 1 is a non-cooled connector cable and non-cooled vehicle inlet for 500 A • Configuration 2 is a cooled connector and non-cooled vehicle inlet for 1500 A • Configuration 3 is a cooled connector and cooled vehicle inlet/conductors for 3000 A SAE J3271 extends the MCS standard with balanced differential signalling over twisted-pair communication wiring that differs from the CCS single-ended power line communication (PLC). The PLC technology is not part of the MCS, which will instead use CAN FD/XL communication. Extensive work is underway to develop vehicle and EVSE communication controllers under the SAE J3271 (harmonised with IEC 61851-23-3) standard. SAE J3271 is also harmonised with IEC TS63379 and ISO 5474 standards to ensure global compatibility and future interoperability. A 4.5 MW MCS manual dispenser for charging marine and construction equipment (Image courtesy of Cavotec)
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