E-Mobility Five E-Charging Options Put to the Test

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Fast charging is the key to the suitability of e-mobility for everyday use. With the ELF project vehicle, Mercedes-Benz has now unveiled a charging laboratory on wheels that is designed to test the limits of what is feasible.

Charging is playing an increasingly important role on the road to widespread electromobility. Battery technology is generally trusted, but customers remain skeptical when it comes to charging. According to a recent Shell study, charging speed, convenience and reliability are the key criteria when choosing a charging location and have a significant influence on route planning and dwell time. Almost 60 percent of those surveyed are not yet convinced of the reliability of charging, and 84 percent of EV drivers would even accept longer distances if the charging point is reliable and convenient.

The charging experience is therefore also a decisive factor when it comes to purchasing an electric vehicle. Mercedes Benz is now trying to get to the bottom of the challenges of charging with a new project. The ELF experimental charging vehicle on wheels aims to combine vehicle innovations with infrastructural concepts to create the most pleasant charging experience possible. To this end, Mercedes-Benz has installed five charging options in a converted V-Class. ELF is capable of ultra-fast charging with over 1,000 watts, as well as solar, bidirectional, inductive and conductive charging.

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In the Megawatt Charging System (MCS), which was originally developed for heavy goods vehicles, the ELF team is primarily testing the thermal load capacity and performance limits of high-voltage batteries, power electronics and charging cables. In order to minimize charging losses, experiments are being conducted with water-cooled cables, as well as with charging robots that automatically connect the heavy cables to the charging socket.

Today, charging via CCS plug is standard. Here too, Mercedes-Benz is exploring the technical limits of the ELF in order to create the conditions for even higher charging capacities. Charging of the ELF mobile is to be carried out in a practical manner along highways or in city areas. Up to 900 kW charging power is already possible in the ELF, which means that 100 kWh can be topped up in ten minutes. Liquid-cooled cables are also used here.

Bidirectional Charging: Key to the Energy Transition

Mercedes-Benz describes bidirectional charging as the "strategic lever for the energy transition". The ELF charging lab on wheels is designed to explore the full potential of this technology. Real-life scenarios will be used to test how electric vehicles can become an active part of the energy system by supplying electricity to the home (vehicle-to-home, V2H), the grid (vehicle-to-grid, V2G) or directly to electrical devices (vehicle-to-load, V2L).

ELF is also testing charging entirely without cables, i.e. via contactless charging systems integrated into the floor. The charging capacity for inductive charging is currently a manageable 11 kW alternating current (AC), which corresponds to a typical wallbox. The focus is on suitability for everyday use, efficiency and compatibility with different vehicle heights. Conductive charging, on the other hand, uses charging plates in the floor that communicate with the vehicle and are connected directly via a connector in the vehicle floor. This requires targeted parking, which is handled by Park Assist. Here too, the charging capacity is currently 11 kW. The major advantages of both technologies are that they are aesthetically pleasing, as there is no longer any need for a charging port on the bodywork and there is no need to plug in a cable, which significantly increases convenience and safety in dubious charging locations.

Solar charging also works wirelessly. Here, the car is the carrier of solar cells, which are located on the roof, for example. When the sun shines, the car produces electricity that feeds the battery.