Audi Centre Brisbane Audi News

Sep 16, 2009

Frankfurt – Audi presents the highlight of the IAA 2009: the e-tron, a high-performance sports car with a purely electric drive system. Four motors – two each at the front and rear axles – drive the wheels, making the concept car a true quattro®. Producing 230 kW and 4,500 Nm of torque, the two-seater accelerates from 0 to 100 km/h in 4.8 seconds, and from 60 to 120 km/h in 4.1 seconds. The lithium-ion battery provides a truly useable energy content of 42.4 kilowatt hours to enable a range of approximately 248 kilometres.

The performance figures are by no means the only evidence of the consistent and holistic strategy. The design makes it clear that the e-tron belongs in the major leagues of sports cars, and the package takes into account the specific realities of an electric vehicle. The battery is directly behind the passenger cabin for an optimal centre of gravity and axle load distribution.

The e-tron is able to freely distribute the powerful torque of its four electric motors to the wheels as required. This so-called torque vectoring allows for dazzling dynamics and an undreamed-of level of agility and precision when cornering.

Audi has taken a new and in some cases revolutionary 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 an innovative thermal management system that is a crucial component for achieving the car’s range without compromising its high level of interior comfort. Networking the vehicle electronics with the surroundings, which is referred to as car-to-x communication, opens new dimensions for the optimisation of efficiency, safety and convenience.

Electric drive systems are still very much outsiders. The first vehicles of this type took to the roads around 1900, yet in 2009 no volume car manufacturer has a car powered exclusively by batteries in its lineup. Fewer than 1,500 electric vehicles are currently registered in Germany, corresponding to only 0.035 percent of all registered vehicles.

Yet electric driving potentially offers numerous advantages. Electric cars reduce the dependence of transportation and the economy on the raw material petroleum. They produce no direct exhaust emissions and thus ease the local burden on the environment. Electric drive systems are also significantly more efficient than combustion engines, consequently making them easier on the customers’ wallets. Other strengths include sportiness and the fun they bring to driving. All of the torque is essentially available the moment the driver steps on the accelerator, allowing for breathtaking acceleration.

There is still a lot of work to do before electric cars are ready for volume production, however. The greatest challenge is the integration of the energy storage system. Acceptable range and performance requires a traction battery that is heavy and takes up a lot of space. Audi is taking a new approach to offset these disadvantages – a holistic approach with a specific vehicle package, a systematic lightweight construction concept and an optimal configuration of all components for the electric drive.

Audi e-tron – The Holistic Approach

The most important development related to batteries for electric drives are lithium-ion cells. Numerous experts throughout the world are working on their further development for use in cars, with the primary objectives being to reduce weight and increase capacity and performance. Audi has also opted for this technology, both for use in a hybrid production vehicle, such as the upcoming Q5 hybrid, and in the e-tron test platform.

The requirement specification for the concept vehicle goes far beyond battery technology and the replacement of the combustion engine with an electric drive system, however. The Audi development engineers decided back in the concept phase to design practically every component and technology based on the new requirements of electric mobility. The interaction of all elements has a decisive influence on the factors efficiency, range and practicality.

The Audi team therefore focused its attention on the total vehicle, which is reflected in the comprehensive requirement specification.

- 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.
- Vehicle safety is on par with the best of today’s production vehicles.
- 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 modelled such a solution in Ingolstadt as part of its “travolution” project.

Design and Package

The caliber of the car is apparent to the observer at first glance. The Audi e-tron has a wide, powerful stance on the road. The car body seems almost monolithic; the closed rear end appears powerful and muscular. The trapeze of the single-frame grille dominates the front end and is flanked by two large air intakes. The top of the grille merges into the flat strips of the adaptive matrix beam headlamp modules with their clear glass covers. High-efficiency LED technology is used for all lighting units – a matter of honor for Audi as the worldwide pioneer in this field.

The headlamps are the core of a fully automatic light assistance system that reacts flexibly to any situation. The new technology recognizes weather conditions and adapts the illumination to rain or fog. The technology at the heart of the light assistance system is a camera that works together with a fast computer to detect oncoming traffic, recognise lanes and measure visibilities, such as in the event of fog.

A new design element unique to the e-tron is the air intakes in the single-frame grille and in front of the rear wheel wells. They are closed flush under normal circumstances and opened by means of flaps when additional cooling air is required. Maximum efficiency is also the reason behind this measure.

The vehicle body is compact. The sweeping line of the front end and the flat curved roof immediately identify the two-seater as an Audi.

The two electric motors, which have their own cooling system, are mounted behind the rear axle. The front electric motors are mounted on the front axle, with their cooling system arranged in front of them. This special package, which features a 42:58 weight distribution, ensures perfect balance, which contributes to the driving dynamics of the e-tron.

Systematic lightweight construction is an even more important prerequisite for efficiency and range with electric vehicles than for conventionally powered automobiles. The Audi development engineers drew on the core competence of the company for the e-tron. The body structure is based on Audi Space Frame (ASF) technology and was realised as a hybrid construction.

Interior and Control Concept

The dash appears to float and has a curve that extends laterally into the door panels. With no need to allow for a transmission, shifter and cardan tunnel, the designers took advantage of the opportunity to create a particularly slim and lightweight centre tunnel and centre console. The flush gear selector, with which the driver chooses between the modes forward, reverse and neutral, emerges from the tunnel when the vehicle is started.

The MMI is controlled via a scroll pad with a touch-sensitive surface on the steering wheel (“MMI touch”) – an element inspired by modern smartphones.

Characteristic for the concept of the Audi e-tron is the near total elimination of switches and small components such as the ignition. The climate control unit is located to the right above the steering wheel. The display provides temperature and ventilation information.

The racing-inspired lightweight bucket seats combine excellent lateral support with comfort. To contrasting colours – snow white and cognac – delineate the various zones of the interior. The colors and the high-quality materials combine elegance and sportiness.

Drive System and Energy Supply

Four asynchronous motors with a total output of 230 kilowatts give the Audi e-tron the performance of a high-output sports car. The concept car can accelerate from 0 to 100 km/h in 4.8 seconds if necessary, and goes from 60 to 120 km/h in 4.1 seconds. The torque flows selectively to the wheels based on the driving situation and the condition of the road surface, resulting in outstanding traction and handling.

The top speed is limited to 200 km/h, as the amount of energy required by the electric motors increases disproportionately to speed. The range in the NECD combined cycle is approximately 248 kilometres. This good value is made possible by the integrated concept: technology specially configured for the electric drive system combined with state-of-the-art battery technology. The battery block has a total energy content of roughly 53 kilowatt hours, with the usable portion thereof restricted to 42.4 kWh in the interest of service life. Audi uses liquid cooling for the batteries.

The energy storage unit is charged with household current (230 volts, 16 amperes) via a cable and a plug. The socket is behind a cover at the back of the car. With the battery fully discharged, the charging time is between 6 and 8 hours. A high voltage (400 volts, 63 amperes) reduces this to just around 2.5 hours. The inductive charging station, which can be placed in the garage at home or also in special parking garages, is activated automatically when the vehicle is docked. Such technology is already used today in a similar form to charge electric toothbrushes.

The battery is charged not only when the car is stationary, but also when it is in motion. The keyword here is recuperation. This form of energy recovery and return to the battery is already available today in a number of Audi production models. During braking, the alternator converts the kinetic energy into electrical energy, which it then feeds into the onboard electrical system.

The Audi e-tron, which is slowed by four lightweight ceramic brake discs, takes the next large step into the future. An electronic brake system 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.

Making its Automotive Debut: The Heat Pump

The heat pump – used here for the first time ever in an automobile – also serves to increase efficiency and range. Unlike a combustion engine, the electric drive system may not produce enough waste heat under all operating conditions to effectively heat the interior. Other electric vehicles are equipped with electric supplemental heaters, which consume a relatively large amount of energy. The heat pump used by Audi – and commonly used in buildings – is a highly efficient machine that uses mechanical work to provide heat with a minimum input of energy.

A high-efficiency climate control system is used to cool the interior. It works together with the thermal management system to also control the temperature of the high-voltage battery.

Driving Dynamics

The normal distribution of the tractive power is clearly biased toward the rear axle in accordance with the weight distribution of the e-tron. Similarly to a mid-engined sports car, roughly 70 percent of the power goes the rear and 30 percent to the front. If an axle slips, this balance can be varied by means of the four centrally controlled electric motors. The electric vehicle from Audi thus enjoys all of the advantages of quattro® technology.

As befitting its status, the Audi concept car rolls on 19-inch tyres with a new blade design. 235/35 tyres up front and 295/30 tyres in the rear provide the necessary grip.

Car-to-x Communication

The electronics development engineers at Audi not only aimed to make the e-tron as efficient and fun to drive as possible, they were also very concerned with safety and traffic management. The technical concept car includes a prototype of an information processing system. Future generations of these systems will usher in a new era in the networking of road traffic, particularly in regions and countries with a high volume of traffic. This progress is made possible by the rapid advancements in computing power, software and communication technology.

The buzzword “car-to-x communication” refers to the direct exchange of information in flowing traffic and to the traffic environment. The letter “x” is a free variable that can refer just as easily to other vehicles as to fixed infrastructure such as traffic lights. In contrast to today’s telematic systems, car-to-x communication no longer requires a central service provider too quickly and effectively pool and process information. The participants themselves perform these tasks by spontaneously networking with one another.

The future car-to-x network still needs some time before it becomes reality on the roads. This obstacle is one that can be overcome, however, as nearly every carmaker in Europe, the U.S.A. and Japan has decided to develop a common standard for hardware and software. Once all new cars are equipped with this technology, a functional network of automotive transmitters will soon be available, at least in large population centers.

These transmitters can be used to open up many new practical applications.