Audi will be adding a 48-volt electrical system to its cars, with examples on how the 48-volt technology will be used in production cars to be revealed later.
“We are using the full bandwidth of electrification in our drive principles strategy. Running part of the vehicle electrical system at 48 volts plays a central role in this,” commented Prof. Dr. Ulrich Hackenberg, Member of the Board of Management for Technical Development at Audi. “It enables us to make more energy available. That paves the way for new technologies with which we can make our cars more sporty, more efficient and more convenient to use.”
According to Audi, the 12-volt electrical systems found in all cars are at the limits. Especially at low temperatures, all the various static?load consumers can account for the entire power generated by the alternator, which can deliver up to 3 kW. 12-volt battery power is no longer capable of meeting the demands of new devices such as electric compressors for forced induction.
The 48-volt system that runs separate from the 12-volt system is a solution. A higher voltage means smaller cable cross-sections are needed; this translates into lighter cable harnesses with lower power dissipation. The 12-volt lead battery’s equivalent is a compact lithium?ion battery supplies 48 volts as the energy source during engine?off phases, with a DC/DC converter supplying the 12-volt system. This is paired to a new efficiency-optimized 10 kW alternator.
A 48-volt electrical system was recently showcased with the Audi A6 TDI concept and RS5 TDI concept earlier this year. The concepts were fitted with an electrically-powered compressor for forced induction, which operates independently of the engine load.
In the concepts, an electric charger complements a normal exhaust gas turbocharger arranged in series. The electric charger’s turbine wheel is powered by a small 7 kW electric motor that can accelerate the compressor wheel up to maximum speed in just 250 milliseconds.
The electric compressor is downstream of the intercooler. At very low engine speeds with low exhaust gas energy at the turbocharger, the bypass valve closes and the air is routed to the electric compressor. This can be flexibly integrated into a variety of forced induction concepts.
The result is a 3.0 litre biturbo V6 that can do 385 horsepower and a peak torque of 750 Nm, which peaks from just 1,250 rpm. Boost pressure is available immediately after each change of gears thanks to the interplay between the electric and exhaust gas chargers.
Audi also says they’ve developed solutions to improve dynamic chassis control based on 48-volt technology as well, with applications in this field to showcased soon.