Audi is upgrading part of its vehicle electrical system from 12 to 48 volts in a bid to increase the power and efficiency of its cars. The move also represents another technical building block for facilitating the integration of new automotive technologies.
The 48-volt system operates independently of the engine load and therefore fundamentally improves the acceleration performance. Moreover, 48-volt technology is ideal for realising convenience systems for dynamic chassis control and Audi will shortly be unveiling a variety of applications in this field.
Audi claims current technology has taken 12-volt electrical systems to their limits, especially at low temperatures, where 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.
As such, Audi's solution is a second subsidiary electrical system running at 48 volts, to complement the 12-volt power supply. The higher voltage means smaller cable cross-sections are needed - which translates into lighter cable harnesses with lower power dissipation. The 48-volt electrical system features new storage technologies and delivers much more power than the 12-volt system with lead batteries.
In the current highest development version, a compact lithium-ion battery supplies 48 volts as the energy source during engine-off phases - a DC/DC converter - integrates the 12-volt electrical system. The lithium-ion battery operates in conjunction with a new, efficiency optimised alternator that qualifies the drivetrain as a mild hybrid.
Within this concept there are diverse ways of starting, controlling and deactivating the combustion engine as needed. The powerful alternator achieves an energy recovery output of 10kW, far more than it is possible at present. That adds up to a saving of up to 10g of CO2 per kilometre, equivalent to fuel consumption of around 0.4L/100km.
