Systematic and user-oriented development of physical interface for vehicle ultrafast charging
Authors: Alexander Mueller, Simon Buck, Fabian Schmiel, Lampros Tsolakidis
Abstract: Status Quo: Electric vehicles currently available on the market have a real maximum range of approx. 400 - 500 km at low temperatures (source: Electric Vehicle Database). The shortest charging time of an electric vehicle is currently approx. 22 min. to charge the vehicle battery with max. 270KW from 5% to 80% (source: PAG).Problem: The range and the time required to refill the energy storage of electric vehicles are not yet as long as those of vehicles powered by internal combustion engines. For the user, these deficits are associated with a loss of comfort, especially on long-distance journeys.Method of Resolution: A promising approach is to significantly reduce the charging time by increasing the charging power with simultaneous and efficient dissipation of the waste heat. Technically, this is to be implemented with a vehicle-external cooling fluid, which is provided by the charging infrastructure. The question arises how the novel thermal interface then necessary can be physically integrated into the charging process, into the vehicle and into the charging infrastructure with special consideration of user requirements. The paper presents the design of three prototype connectors, using the standardized product development method described in VDI 2221. Requirements are defined from the analysis of the competitive environment and the required integration of a thermal interface. On the one hand, the focus lies on the technical and physical requirements related to the electrical and thermal power transmission, on the other hand, the human-product requirements related to the physical use are assigned special importance. For the conception, the derivation of Function Structures and subsequently the identification of all sub-functions serves as an essential basis. Partial functions of the interface that have proven themselves in the electrical power transmission of the standardized CCS interface (source: IEC 62196-3 / SAE J1772) are adopted. Essentially, the sub-functions "leakage-free coupling / decoupling", "overcoming closing resistances" and "user-friendly connector handling" are identified as design-critical. By defining and selecting suitable versions of the sub-functions, three interface concepts are systematically derived and evaluated against each other in test person studies. The result shows that vehicle ultrafast charging with electrical and thermal power transfer and with only one connector is possible for all users and all vehicle types from an ergonomic point of view. A test person study shows that the users prefer the handling of the new interface compared to the charging standard currently used on the market and a separate, hydraulic power transmission.
Keywords: Ultrafast charging, fast charging, electric vehicle, EV, automotive ergonomics, user-centered vehicle design, RAMSIS, function structure
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