Audi makes the leap to (partial) 48V supply

August 25, 2014 // By Christoph Hammerschmidt
Carmaker Audi has announced to partly equip its cars with an 48V electrical system. The split-voltage system gives automotive electrics and electronics designers the option to electrify additional units for the sake of overall efficiency.

The company recently demonstrated prototypes of existing models A6 TDI and RS 5 TDI equipped with the 48V technology. Both vehicles featured an electrically driven air intake ompressor which works independently of the engine rpm and thus offers "fundamental" improvements in terms of acceleration behaviour, the company says. Now a company spokesperson said the technology will enter series production within the "next two years."

And this is the rationale of electrifying more and more units in the vehicle: Electrically-driven oil and coolant pumps, power steering and other dynamic subunits provide higher overall efficiency if they are driven by electric motors; and since the plethora of electric loads in cars increasingly drives the 12V power system to its limits, automotive electric system developers see the solution in an additional, separate 48V system. Such systems have been advocated by electric system designers for years; in 2011 top developers from Audi, BMW, Daimler, Porsche and Volkswagen have announced the introduction of such systems at an engineering congress in Ludwigsburg, Germany.

Now it seems that at least Audi has driven the development to series maturity. "In our drive principles strategy we are utilising all options of electrification", explained Ulrich Hackenberg, Member of the Management for Technical Development at the Ingolstadt, Germany, based carmaker. "Running part of the vehicle electrical system at 48 volts plays a major role in this strategy. It enables us to provide more energy to these systems (than with conventional 12V system). This is a precondition for the introduction of new technologies that help us to make our cars more sporty, efficient and comfortable."

With today's 12V systems, the high number of static loads in a car brings the alternator with a maximum output power of 3 kW to its limits, especially at low temperatures. The alternator power is typically not sufficient to supply innovative dynamic loads. The 48V subnetwork can supply such loads such as the abovementioned rpm-independent compressor. In