The Car and Truck Fleet and Leasing Management Magazine

Audi Reveals the Purely Electric e-tron

September 21, 2009

NGOLSTADT/FRANKFURT, GERMANY - Audi presented the e-tron, a high-performance sports car with a purely electric drive system at the 2009 Frankfurt Auto Show. Four motors - two each at the front and rear axles - drive the wheels, making the concept car a true quattro. Producing 313 hp and 3,319.03 lb.-ft. of torque, the two-seater accelerates from 0 - 62.14 mph in 4.8 seconds, and from 37.28 - 74.56 mph in 4.1 seconds. The lithium-ion battery provides an energy content of 42.4 kilowatt hours to enable a range of approximately 154 miles.

The e-tron is able to freely distribute the torque of its four electric motors to the wheels as required. Audi has taken a new approach to many of the technical modules. A heat pump is used to efficiently warm up and heat the interior. The drive system, the power electronics, and the battery are controlled by a thermal management system that is a crucial component for achieving the car's range without compromising its interior comfort. Networking the vehicle electronics with the surroundings, which is referred to as car-to-x communication, opens new dimensions for the optimization of efficiency, safety, and convenience.

The Audi team therefore focused its attention on the total vehicle, reflected by:

  • The reduction of road resistances and the resulting increase in range plays a major role with electric vehicles. Lightweight construction was therefore a top priority for the e-tron concept car. The body, in particular, combines low weight with supreme strength and rigidity. An intelligent aerodynamics concept with active elements helps to reduce consumption.
  • The package ensures the safe integration of the electric drive system and the battery. Placing the battery in front of the rear axle ensures an optimal axle load distribution without compromising the compact overall design and the generous amount of interior space.
  • Advanced battery technology enables a practical range. The battery system is water-cooled for optimal performance and service life.
  • A needs-based energy management system controls all functions for the chassis, convenience equipment and other auxiliary consumers.
  • The innovative thermal management system with optimally matched cooling and heating components considers the cooling requirements of the battery and the drive system in addition to the interior temperature.
  • Driving dynamics and road comfort are what Audi customers have come to expect in the sports car segment.
  • Vehicle safety is on par with the best of today's production vehicles.
  • The driver is provided with clear and comprehensive information.

The e-tron concept car uses car-to-x communication technology developed by Audi to improve the efficiency of conventionally powered vehicles. For example, information about traffic light cycle times and the flow of traffic - provided by the infrastructure and other vehicles - is used to compute an optimal driving strategy. Audi has already modeled such a solution in Ingolstadt as part of its "travolution" project.

Four asynchronous motors with a total output of 313 hp. The top speed is limited to 124.27 mph, as the amount of energy required by the electric motors increases disproportionately to speed. The range in the NECD combined cycle is approximately 154 miles. Audi uses liquid cooling for the batteries.

The battery is charged not only when the car is stationary, but also when in motion. During braking, the alternator converts kinetic energy into electrical energy, which it then feeds into the onboard electrical system.

The Audi e-tron, slowed by four lightweight ceramic brake discs, has an electronic brake system that makes it possible to tap into the recuperation potential of the electric motors. A hydraulic fixed-caliper brake is mounted on the front axle, with two novel electrically-actuated floating-caliper brakes mounted on the rear axle. These floating calipers are actuated not by any mechanical or hydraulic transfer elements, but rather by wire ("brake by wire"). In addition, this eliminates frictional losses due to residual slip when the brakes are not being applied.

This decoupling of the brake pedal enables the e-tron's electric motors to convert all of the braking energy into electricity and recover it. The electromechanical brake system is only activated if greater deceleration is required. These control actions are unnoticeable to the driver, who feels only a predictable and constant pedal feel as with a hydraulic brake system.


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