Fraunhofer Institute for Transportation and Infrastructure Systems IVI
Fraunhofer Institute for Transportation and Infrastructure Systems IVI

Underbody Charging System

© Fraunhofer IVI

Underbody Charging System UBCS

Automated charging: Saving costs, using space efficiently, increasing safety

To operate electric vehicles efficiently, large amounts of energy must  be transferred in a very short time, similar to conventional fueling

For this purpose, Fraunhofer IVI has developed a compact, safe underbody charging system meant specifically for vehicle fleets in logistics, municipal operators, and even in the private sphere. The charging process starts and ends at the push of a button – no manual plugging in is needed. The automated contact system connects vehicles and infrastructure in a space-saving way, is capable of high-current charging and complies will all safety standards.

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Key element for intelligent charging infrastructure

Compact and protected

The underbody charging sysatem requires no additional space for charging infrastructure at the charging point.

The system has no above-ground power lines and offers no points of attack for cable theft and vandalism.

Intuitive and safe

The charging process is automated and starts at the push of a button, which means that there is no need to handle heavy cables and plugs.

The system can be operated without contact with electrical components. No additional training is required.

Future-ready and scalable

The system is built for extremely high charging voltages (passenger cars: 1000 V, trucks: 1250 V) and very high charging power (passenger cars: 1.2 MW, trucks: 4.5 MW).

It is optimally suited for today's use cases and can be easily adapted to future fast charging requirements without any costly conversion or retrofitting. 

Fully automated fast charging

The underbody charging system's functioning principle explained.

UBCS Underbody Charging System
© Fraunhofer IVI
UBCS Underbody Charging System.

A range of different systems for charging electric vehicles are available at the market today. If high power levels are to be transmitted, only conductive, i. e., contect-based systems (charging cable with plug) are currently an option. These solutions are flexible, but they limit the performance of the system to ca. 130 to 150 kW charging power and are therefore not suited for fast charging systems with higher power levels.  

Fraunhofer IVI has developed a fully automated charging system for this specific operation scenario that overcomes the limitations of conventional plug-and-cable devices.

With this new technology, it is possible to transmit up to 1.2 MW of electrical power to passenger cars and up to 4.5 MW to trucks. Alls of this happens without the intervention of an operator and in a fully automated, safe and reliable way. The system is distinguished by 

  • only one interface for different charging power levels, 
  • no limitations regarding charging power, as well as 
  • high operating comfort through full automation.

This means that handling charging cables will soon be a thing of the past.

Areas of application

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Vehicle fleets

The underbody charging system provides automated charging for logistics enterprises, municipal services, emergency vehicles, and company cars without requiring additional space. Through its space-saving integration into the ground, it makes efficient use of existing parking spaces and lots. The system is operational today at lower power levels, and it can be expanded in the future for higher power levels without any costly conversion or retrofitting work, which makes it ideal for municipal waste disposal services or other enterprises with large vehicle fleets.

 

© Fraunhofer IVI

Practical test with municipal waste disposal service

Charging at the push of a button: Stadtreinigung Dresden tests underbody charging system

Fraunhofer IVI and Stadtreinigung Dresden GmbH are launching a practical test of an automated charging system that improves the efficiency and safety of charging electric vehicles in municipal logistics operations.

Read more
 

© Fraunhofer IVI

Agriculture, industry and construction

Electrically driven agricultural machines and devices require reliable and robust charging units that perform well even under difficult operating conditions. For this purpose, the underbody charging system can be integrated into vehicle trailers that allow charging at the edge of fields. Beyond that, similar options can be implemented for industry and the construction sector, e. g., for machines, cranes and other performance-intensive applications.
Read more
 

Filling station and charging parks

Due to the road-integrated charging solution's robust, durable construction and minimal maintenance needs, electric charging becomes as fast as conventional refueling. The compact charging unit is fitted into a shaft system and dug into the road, while vehicles can simply drive over it. This way, up to 20 charging processes per hour can be realized using only one contact system.

Read more
 

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Car parks and parking garages

The system's flexible, easily installed variant allows comfortable charging in public car parks and on industry premises. The system is simply placed on top of the road and can be easily integrated due to its compact dimensions. It can charge vehicles for up to 600 km range within 5 hours and is thus ideal for use in private and semi-public areas.

Read more
 

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Flexible charging solution

The flexible charging device provides a comfortable charging option in garages for car fleets, light commercial vehicles, caravans and private passenger cars. The compact system is simply placed on the road surface and can be easily integrated. 

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UBCS vehicle interface

ACD counterpart

view of UBCS vehicle interface from below
© Fraunhofer IVI
Compact, robust and easily integrated: the charging system's vehicle component.

During the development process, special attention was paid to the technology's simplicity and maintenance-friendliness. In accordance with the manufacturers, the vehicle component had to be particularly small, lightweight, and cost-effective due to the high number of units expected to be produced.

 

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Safety and standardization

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If the charging intervals are to be short, high system voltages of up to 1250 VDC and high charging currents of up to 2000 A and above are required. As aconsequence, the contact systems must be constructed in an especially safe and reliable way.

This applies to touch protection, the prevention of arcing or unwanted heating, and to safe and secure charging process control. In addition, fundemantal safety regulations regarding, e. g., getting caught and slipping, were observed.

Fraunhofer IVI supports the further development of their systems by active participation in the following standarization bodies and interest groups on a national and international level: 

  • Founding member of the DKE working group 353.0.13 (Automated Conductive Charging)
  • Member of the international IEC-TC69-WG14 mirror body (EV supply equipment with automated connection of a vehicle coupler), standardization mandate issued for IEC 61851-26 / -27 
  • Solution proposal "Automated Charging Device Underbody (ACD-U)" for private and public charging (Annex D of future IEC 61851-26 standard, currently in draft stage)
  • Deputy manager of working group "ACD-U" within Charging Interface Initiative e. V. (CharIn)
  • Founding member of DKE working group 542.4.8 (ACD-U interface) for IEC 61851-26
  • TS IEC 61851-27 published for comments, publishing of TS IEC 61851-26 imminent
  • Participation in DKE working group 353.0.02 (Mega Charging System MCS)
  • Member of project group IEC PT63644 (ACD-U Interface) for IEC 61851-26

 

Projects and references

MEGA-LADEN

  • Development of a comprehensive charging concept offering solutions for all aspects of the charging process
  • Solutions for vehicle integration, communication with vehicles, the infrastructure and fully automated charging
 

EDDA-Bus

  • World's first electric city bus with automated charging at terminal station
  • Tested in regular operation at Dresdner Verkehrsbetriebe AG
project website

AULA

  • Successful integration of an underbody charging system into a road surface
  • Integration of a vehicle interface into a series vehicle (VW E Golf) and demonstration of automated charging
project website

Charging Mobile UWB - CMUWB

  • Development of an independently positionable charging robot for the automated charging of electric cars in a garage scenario and of a vehicle interface for integration into the underbody of electric cars.
learn more

FAQ

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  • The system is a conductive energy transmission system. This means that electrical contacts are physically connected to each other. The Underbody Charging System (UBCS) uses the face-contact coupling principle. By way of this principle, the electrical contacts are pressed together with great force. To ensure that this electric connection is maintained throughout the entire charging process, an electromagnetic locking mechanism between the charging unit's road component and the UBCS vehicle interface is activated.

    This innovative technology significantly reduces transmission losses, which allows much more current to be transmitted via a contact point without active cooling.

  • Both variants of the system are automated solutions that require no manual handling of cables and plugs for charging.

    The flexible charging unit is suitable for a wide range of vehicles and applications. Its scope ranges from charging your own car in your home garage to industrial and mobile applications in the commercial vehicle sector.   

    The road-integrated variant of the system basically requires no installation surface and is therefore especially well-suited for depots and other environments where space is critical. In addition, it is a discreet solution for areas where no above-ground charging stations can be installed for reasons of urban planning (historical monument protection, sightlines). Because it is traversable, it cannot be crashed into. The system is securely protected against vandalism and cable theft. Due to its automated character, it is especially well-suited for automated vehicle applications. It is a safe investment into future applications because of its high potential charging capacity.

  • The system is compliant with the newly published IEC 61851-26 standard.

    The capacity of the road-integrated variant's electrical interface exceeds the requirements of a Megawatt charging system (MCS). It is capable of carrying out charging scenarios with capacities of 22 kW to 4.5 MW.

    The flexible charging unit is capable of carrying out charging scenarios with capacities of 22 kW to 300 kW.

    Both variants can be integrated into any vehicle.

  • The charging unit is integrated into the road via a plastic cable duct or shaft. The civil engineering work does not differ from conventional installation, for example in the area of broadband cable expansion. Drainage pipes and cable ducts also need to be planned for at the shaft.

    The road surface cover including the cover flaps is a special custom component. It has to be fitted in horizontal level into the road surface.

  • The installation surface should be flat and level. Concrete, asphalt, or tile floors are all suitable surfaces.

  • The charging interface connects directly to the charging station (road-integrated version) or a wallbox (flexible unit). This means that conventional charging cables are not needed.

  • Yes, both system variants are designed so that persons can step on them and vehicles can drive on/ over them.

    The road-integrated variant features a road cover with integrated cover flaps. The assembly was tested in conformity with DIN EN 124 for the D400 load class, which proves its suitability for road surfaces in public spaces. Depending on the specific use case, other load classes can also be achieved. The cover flaps are locked in idle state and protect the system from unauthorized access. Due to the fact that the charging cables lie securely under the road surface, cable theft is impossible.

  • The flexible unit is designed for outdoor use and can be operated on dirty road surfaces. However, we advise that you clean the installation surface regularly.

    The road-integrated variant is equipped with a drainage system that extracts rain water and dirt from the cable duct. The road cover is designed to prevent the accumulation of dirt in the area around the cover flaps. In case of strong contamination, the road cover can be easily cleaned with a broom. A heating unit also protects the road cover from freezing. In the event of flooding, critical water levels will be detected via an integrated float switch and the system will be shut down.

  • The flexible unit will independently adjust to the right postion underneath the vehicle. As a prerequisite, the vehicle must be parked so that the UBCS vehicle interface lies within a 50 x 50 cm area surrounding the charging unit.

    The road-integrated variant can compensate positioning tolerances of 70 mm and angle tolerances of 10 ° in each direction. It can be accessed from two opposite directions.

    Vehicles with ground clearances of 80 to 320 mm can be charged, which includes all vehicle classes from sports cars to trucks.

  • Vehicles must be in the correct position above the charging system and the parking brake must be engaged.

    Wireless communication between vehicles and charging station will initiate the charging process. The communication can either be carried out fully automatically or via the push of a button located inside the vehicle or on the charging station.

  • If the charging process is aborted, the charging contactors open automatically and the electromagnetic lock is disengaged. 

    The flexible charging interface will return into its initial position so that the vehicles can evacuate the charging area. During this process, the prescribed sequence for disconnecting the electrical contacts is observed.

    The road-integrated charging interface will retract into the charging duct and the road cover will close and lock automatically so that the vehicles can evacuate the charging area. 

    During this process, the prescribed sequence for disconnecting the electrical contacts is observed.

  • Yes. The charging interface stays connected to the UBCS vehicle interface via the electromagnetic locking mechanism. The system will compensate for all dynamic movements of the vehicle that occur during the charging process.

  • Fraunhofer IVI offers their industry partners diverse development and cooperation options. This includes:

    • Joint research projects: Development of innovative technology in the fields of transport engineering, mobility and automation.
    • Technology transfer: Support for the transfer of research findings into industrial application, including attractive licensing plans for our patented technologies.
    • Access to an expert network: We promote synergies and cooperation through our access to a broad network of experts and other enterprises.

    Please contact us to find the proper solutions for your challenges.

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