In the joint project "evTrailer2", researchers at the Fraunhofer Institute for Structural Durability and System Reliability (LBF) have developed a hybrid storage system for electric tractor-trailers. This was reported by Fraunhofer LBF recently. The system combines high-energy and high-power cells in order to shorten charging times, increase charging power, and prolong the life of the batteries. This increases the range of electrically powered tractor-trailers.
The project "Electrical Drive Cooperation and Energy System for Heavy Commercial 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 semi-trailers
with a gross vehicle weight of over twelve tons through innovative electric traction systems. According to Fraunhofer LBF, the use of hybrid storage helps to control energy flows more efficiently and reduce the load on the 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 align with the respective operating conditions of the vehicle, for example route length, road profile, or the charging and recuperation phases. Through the mission-specific regulation of energy flows, the storage can guarantee both high range and a longer
service 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 power
In tests, the researchers achieved charging powers of up to 350 kilowatts at fast charging stations and up to 500 kilowatts on overhead line routes or megachargers. The recuperation 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 extend the lifespan, the charge window 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 drive train, but also protects the high-energy cells from harmful current spikes. Transport and logistics companies benefit, according to the institute, from reduced operating costs and a better environmental footprint due to the increased efficiency and sustainability of the drive
