The synchronous electric motor of the Audi A1 e-tron is mounted transversely at the front of the car. Its low mounting position has a positive effect on the vehicle’s centre of gravity. Continuous output is rated at 45 kW, with peak power of 75 kW available in short bursts. 150 Nm (110.63 lb-ft) of torque is continuously available, and peak torque is 240 Nm (177.01 lb-ft).
The electric motor sends its power to the front wheels via a single-speed transmission. The elegant, retractable selector lever on the console of the centre tunnel used to choose between “Drive,” “Reverse,” and “Neutral” was taken from the first Audi e-tron.
The power electronics are mounted in the engine compartment above the electric motor. The most important components are the pulse-controlled inverter, which serves as the controller between the electric motor and the battery; the DC converter, which connects the high-voltage network with the 14 volt electrical system; a breaker unit to protect the high-voltage components; and the charging module. The socket for the standard charging plug is located behind the rings in the single-frame grille of the Audi A1 e-tron. A fully depleted battery can be recharged in approximately three hours from the 380 volt grid. A display immediately adjacent to the plug-in connection shows the current charge status and the charging time remaining.
The concept of the innovative Mega City Vehicle requires the electrification of key auxiliaries. The refrigerant compressor of the climate control system, for example, is electrically powered by a high-voltage electric motor that supplies only the amount of power needed at the time.
This increases system efficiency substantially compared to conventional concepts. Thanks to a special circuit, the climate control loop also functions as a heat pump that regulates the temperature of the cabin and the battery.
The power steering of the Audi A1 e-tron is electro-mechanical and thus particularly energy-efficient. 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. In addition, the servo unit received a new, demand-controlled electric vacuum pump.
The large electric motor powering the A1 e-tron can convert braking energy into electric current and feed it back into the electrical system. The high degree of recuperation benefits overall efficiency. The electric control actions are imperceptible to the driver, who notices only the familiar, precise, and perfectly controllable pedal feel.
The battery pack: a compact T arranged below the floor
The energy storage unit is arranged below the floor, where it is ideal for the centre of gravity and weight distribution. The battery pack is shaped like a T, with the short “transverse beam” filling the rear section of the centre tunnel and the “cross-beam” filling that area in front of the rear axle where the fuel tank is otherwise located. The 380 volt lithium-ion rechargeable battery has a nominal energy content of 12 kilowatt hours. It comprises 96 prismatic cells and weighs less than 150 kilograms (330.69 lb).
The Audi A1 e-tron can drive 50 kilometers (31.07 miles) emission-free in city traffic on the powerful battery. On longer trips, the battery is recharged by a particularly compact internal combustion engine mounted below the luggage compartment.
The range extender
The A1 e-tron concept car has a Wankel engine as a range extender, but other compact concepts are also possible. The small single-rotor Wankel has a chamber volume of 254 cc and runs at a constant 5,000 rpm in its peak efficiency window. The electronics also consider navigation data such as the destination and route profile to automatically activate the range extender as needed. The driver can also turn the range extender on and off as necessary with the push of a button The fuel tank holds 12 liters (3.17 US gallons).
The great strengths of the Wankel engine are the nearly vibration-free and quiet operation, the small dimensions, and the extremely low weight. Together with the generator, which is powered by the Wankel engine and produces 15 kW of electric power, the complete assembly weighs only around 70 kilograms (154.32 lb). This weight also includes the special power electronics, the intake, exhaust, and cooling unit, plus the insulation and the subframe.