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Audi electrifies in-car systems with 48V tech

Posted: 28 Aug 2014     Print Version  Bookmark and Share

Keywords:Audi  48V  electrical system  automotive 

Audi is wiring up its cars with 48V subnetwork, providing the electrical system with more voltage and power for the integration of new automotive technologies. The split-voltage concept will give automotive electronics designers the option to electrify additional units, facilitating overall efficiency.

The carmaker recently demonstrated prototypes of existing models A6 TDI and RS 5 TDI equipped with the 48V technology. Both models were fitted with an electrically powered compressor operating independently of the engine load—the result was an improvement in acceleration performance. The technology is expected to enter series production within the next two years.

The rationale behind electrifying more and more units in the vehicle is to enable electrically-driven oil and coolant pumps, power steering and other dynamic subunits—convenience systems that drive dynamic chassis control. In addition, the 48V technology will particularly be beneficial since current technologies are taking 12V electrical systems to their very limits.

At low temperatures, for example, all the various static-load consumers can account for the entire power generated by the alternator, which can deliver up to 3kW. The battery power is no longer capable of meeting the demands of new, dynamic-load consumers such as high-performance electric compressors.

A second subsidiary 48V electrical system to complement the 12V power supply proves to clear up the mentioned bottlenecks. The higher voltage means smaller cable cross-sections are needed, giving way to lighter cable harnesses with lower power dissipation.

For years, automotive electrical system designers have advocated split-voltage systems, which were initially introduced in 2011 by top developers from Audi, BMW, Daimler, Porsche and Volkswagen at an engineering congress in Ludwigsburg, Germany.

Now it seems that Audi at least has driven the development of the technology to commercial application. "We are using the full bandwidth of electrification in our drive principles strategy," said Dr. Ulrich Hackenberg, member of the Board of Management for Technical Development at Audi.

Hackenberg said: "Running part of the vehicle electrical system at 48V 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."

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Benefits of the 48V system: additional power and efficiency. Source: Audi

The 48V electrical system is connected to the 12V system through a two-way DC/DC converter that employs innovative energy storage technologies and provides significantly higher power levels than the conventional system. Audi regards this technology as an important building block of its strategy to further drive the electrification of in-car systems. The carmaker said it has already developed a scalable modular platform concept that includes a version that integrates the electric compressor.

The highest version of the platform being developed utilises a 48V lithium-ion battery as energy source for phases when the engine is off. This battery works in conjunction with an energy-optimised alternator that provides an output of up to 10kW, effectively turning the car into a mild hybrid.

Within this concept there are diverse ways of starting, controlling and deactivating the combustion engine as needed. This adds up to savings of up to 10g of CO2 per kilometre, equivalent to around 0.4l of fuel per 100km.

- Christoph Hammerschmidt
  EE Times Europe

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