As part of the 25th Aachen Symposium in Germany, component major Schaeffler is showcasing its ‘High Performance 48 Volt’ concept vehicle. With a permanent, purely electric 20 kW performance, the concept provides an economical and efficient 48 Volt mild hybridisation.

Automobiles have had a 12 Volt on-board electric system for over 40 years. The voltage on tomorrow's automobiles will be changing from 12 to 48 Volts. Essentially, modern automobiles are using less and less fuel while the vehicle's demand for electricity is increasing due to number of electronic and elctromechanical components. Many functions which were previously purely mechanical are now increasingly electromechanical. Innovative active roll control, electrically controlled turbochargers, advance climate control without using the internal combustion engine as well as stop-start engine systems and mild hybrid architectures are the drivers for a 48 Volt power source. Hybrid concepts are a vital building block in the design of more efficient vehicles with combustion engines.

The concept’s electric axle

The Schaeffler High Performance 48 Volt concept vehicle features a drive architecture containing an ‘electric axle’ comprising an electric motor on the rear axle. Experts call this a P4 arrangement. The integral high-performance drive of the Schaeffler High Performance 48 Volt system provides 20 kW of permanent, purely electric performance. The electric axle complements the internal combustion engine which drives the front axle. In the demonstrator vehicle, it is connected to a belt-driven starter generator and also operates at a voltage of 48 Volts.

The Schaeffler electric axle produces a starting torque of up to 2,000 Nm. This provides purely electric driving up to 35kph as well as active ‘sailing’ at speeds of more than 70kph. A further feature of the integral two-speed electric axle is the possibility of torque vectoring, i.e. selectively distributing the drive forces to specific wheels. This improves the agility and safety of the vehicle and the electric axle provides the vehicle with all-wheel drive functionality when combined with the front-wheel drive. The energy generated during braking is fed back into the energy system via the recuperation function in most of braking operations which reduces consumption significantly. Furthermore, the electric motor and the power electronics are combined into one unit in the Schaeffler electric axle, making important savings in terms of space and mass.

It is already clear that concepts for 48 Volt hybrid drives are becoming increasingly important. High volumes are anticipated in the future. The hybrid structure will be defined by the position of the electric motor in the powertrain. The 48 Volt motor can be located in any number of different configurations in the vehicle, depending on the design of the system. Schaeffler says it is providing products for an electrified, 48 Volt future for all hybrid topologies (P0 to P4).