Like many automobile manufacturers, Audi plans to compete in the electric car market. It recently unveiled its Audi A2 Concept, a pure electric vehicle. The Audi A2 is a five-door, four-passenger city car with small external dimensions It has an overall length of just over 149 inches, about 25 inches shorter than the Nissan Leaf. The Audi A2 Concept can accommodate a special city bicycle between the seats and in the rear cargo compartment.
Audi’s A2 Concept uses a lithium-ion battery pack that stores 31 kilowatt hours of energy, of which 24 kilowatt-hours is usable. Typically, about 80 percent of an EV's battery capacity is available for propelling the vehicle. Lithium-ion batteries packs prefer a partial cycle rather than a deep discharge, since deep discharging can reduce battery life. They don't have the ‘memory effect’ found in some other battery chemistries.
The battery powers an electric motor rated at 116 horsepower of peak power and 199 lb-ft torque. This gives the lightweight, 2535 pound EV a governed top speed of 93 mph with 0 to 62 mph acceleration of 9.3 seconds. The lithium-ion battery pack is located in the sandwich floor and the electric motor is transversely mounted in the front of the vehicle, driving the front wheels via a single-speed transmission. The A2 Concept features electric steer-by-wire and brake-by-wire systems.
A driving range of 124 miles is achieved under the European driving cycle. It takes roughly 1 1/2 hours to fully recharge the battery using 400 volt, three-phase European current and about four hours when using 230 volt household current. It is also designed for Audi Wireless Charging. Here, a driver pulls the car over a parking spot that contains a primary coil. Electrical energy is automatically transferred inductively to a secondary coil in the EV, which in turn transfers power to the battery pack. Audi says contactless Audi Wireless Charging takes about the same amount of time as other charging technologies.
The car's relatively light weight is achieved through the use of Audi Space Frame (ASF) technology combined with hybrid multi-material construction. Here, very different materials are combined to achieve ultra light weight. For example, the superstructure is made largely of aluminum components and complemented with carbon fiber-reinforced polymer (CFRP) components. The 18-inch wheels are fabricated using cladding technology, in which the alloy base wheel and cladding are manufactured separately and bonded together, to greatly reducing the amount of material used. In the Audi A2, this saves about 4.4 lb per wheel.
The Audi A2 Concept car features an opaque glass roof finished in flat Electric White that becomes transparent at the push of a button. When an electric voltage is applied, small particles integrated into the glass align so the light can pass through the glazing unhindered. When the glass roof is darkened it blocks infrared sunlight almost completely. This helps temperature management of the interior, important in battery electric vehicles.
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