Researchers at the Fraunhofer Institute for Structural Durability and System Reliability (LBF) have, in the joint project "evTrailer2", developed a hybrid storage system for electric tractor-trailers. The system combines high-energy and high-performance cells to shorten charging times, increase charging power, and extend the life of the batteries. This increases the range of electric tractor-trailers.
Project to improve efficiency in freight transport
The project "Electric Drive Cooperation and Energy System for Heavy-Duty Vehicles – evTrailer2" is funded by the Federal Ministry for Economic Affairs and Climate Action. The aim of the research is to improve the energy efficiency of heavy tractor-trailers with
a gross vehicle weight rating of over twelve tonnes through innovative electric traction systems. According to Fraunhofer LBF, the use of hybrid storage helps to manage energy flows more efficiently and reduces the load on battery cells.
Mission-adapted control of energy flows
According to the researchers, the concept is based on an optimal distribution of storage capacity between high-energy and high-power cells. This control should be oriented to the vehicle's operating conditions, such as route length, road profile, or the charging and recuperation phases. Through the mission-specific control of energy flows, the storage can ensure both high range and a longer
life.
Two storage types for different power requirements
The developed system uses two drive axles. The high-energy storage supports the vehicle during steady driving, while the high-power storage becomes active during acceleration and on inclines. Through dynamic load distribution between the two components, outputs of up to 600 kilowatts can be delivered during acceleration.
High charging and recuperation powers
In tests, the researchers achieved charging powers of up to 350 kilowatts at fast charging stations and up to 500 kilowatts on overhead contact lines or megachargers. The recovery of braking energy is up to a maximum of 348 kilowatts. The total
storage has a capacity of 122 kilowatt-hours, of which 98 kilowatt-hours are usable. To increase the lifespan, the charge depth is limited to 50 percent of the gross capacity. This should enable the system to achieve a mileage of more than 700,000 kilometers.
Contribution to efficiency improvements in freight transport
According to Fraunhofer LBF, the hybrid storage system not only improves the efficiency of the electric drivetrain but also protects the high-energy cells from harmful current peaks. Transport and logistics companies benefit from reduced operating costs and a better environmental balance through the increased efficiency and sustainability of the drive system.
