User-Centered Development and Evaluation of a Physical Ultrafast Charging Interface

IntroductionThe CoolEV consortium, consisting of Porsche, Hydac, ZSW, IFS and the University of Applied Science Esslingen (UAS Esslingen) is currently working on the fast charging station of the future. In this context, the UAS Esslingen is developing a new type of charging interface, which, in addition to the electrical lines, also provides fluid lines for temperature control of the vehicle battery. Main research areas of the current work are a user-friendly physical charging interface and the overall operating concept of the charging process. The novel interface and the evaluation of user-friendliness are highlighted in this contribution.ProblemState of the art CCS charging connectors have added cooling to the contacts and the electrical lines, in order to prevent overheating within the connector [1]. The remaining bottleneck in charging speed now is the vehicle battery. To control its temperature, the novel charging interface, developed in the CoolEV consortium, provides two fluid lines, adding the capability of externally cooling the vehicle. Disadvantage of this addition is an increase in size, weight and line stiffness, compared to current charging connectors. This could cause problems concerning handling or carrying for a user. There needs to be a verification, if the interface is still usable for everyone and for all types of electric vehicles. Another question in need of an answer is, if a person would prefer the combination of fluid and electrical lines in one plug or a solution consisting of two separate plugs, keeping the CCS connection and adding a second line for the fluid.Method of ResolutionTwo different trials were held to answer the questions that were brought up while developing the physical interface. At first, a test rig with an adjustable ergonomics model of the new hand piece was built. The sockets, simulating the vehicle side of the rig, are arranged in two different heights, both on opposite ends of a comfort zone, determined by means of the digital human-model RAMSIS® [2]. Using this rig, 30 participants were guided through the experiment, each using the new interface and subsequently answering a questionnaire about their experience. For an objective review of the experience, every participant was also filmed while conducting the charging process. Using the videos different problems were identified, mostly involving body position and sight of the vehicle socket, giving inputs for improvement of the hand piece. For the second trial, the rig was extended with an assembly containing the dual line solution. The improved hand piece was 3D printed and added to the single line solution. In a comparison experiment, 30 participants used both variants and rated their experience, resulting in the identification of a user favourite. The experiment results prove that a one line solution is usable for everybody and preferred to a dual line solution. The significance of the results were statistically tested and secured.[1] PHOENIX CONTACT Deutschland GmbH, “High Power Charging – die Technologie für Schnellladestationen,” 2021. [Online]. Available: https://www.phoenixcontact.com/online/portal/de?1dmy&urile=wcm:path:/dede/web/main/products/technology_pages/subcategory_pages/High_power_charging/b1c8a245-f088-4fad-b144-cea31e7f9a82.[2] Human Solutions GmbH, “3D-Menschmodell & Ergonomiesimulation,” 2021. [Online]. Available: https://www.human-solutions.com/de/produkte/ramsis-allgemein/index.html.