A closer look at Audi’s new R8 e-tron EV and battery

The model line-up of the second generation of Audi’s high-performance R8 sports car, unveiled at the Geneva Motor Show earlier this year, includes the new R8 e-tron battery-electric vehicle. The new R8 e-tron delivers 340 kW (456 hp) of power; acceleration from 0 to 100 km/h (62.1 mph) in 3.9 seconds; and a driving range of up to 450 km (279.6 mi). Range for the first generation R8 e-tron was was 215 km (133.6 mi).

Available for order this year upon customer request, the new R8 e-tron uses a newly developed high energy density Li-ion technology optimized for a purely electric vehicle drive. Li-ion cell energy density was increased from 84 to 152 Wh/kg; in comparison to the first technology platform, the battery capacity has grown from 48.6 kWh to 90.2 kWh—without changing the package.

R8 Overview. Visually, the 4.40 meter (14.4 ft) long Audi R8 e-tron is recognizable by its unique lighting solutions on the air inlets, front apron and sideblades. Its exterior skin, painted in Magnetic Blue, combines body parts made of aluminum and carbon fiber reinforced polymer (CFRP), such as the front and rear lids.

The R8 e-tron Audi Space Frame (ASF) is based on the multimaterial design of the V10 version, which is extended by a rear body module made of CFRP. Despite its low weight, the corrugated bulkheads that conceal the luggage compartment can absorb a lot of energy in a rear-end collision.

With aerodynamic modifications to its cooling air inlet, rear spoiler, diffuser, underbody and sideblades, the drag coefficient (Cd) of the R8 e-tron is just 0.28.

The T-shaped Li-ion battery is structurally integrated in the middle tunnel and is mounted behind the occupant cell—this location offers a low center of gravity and an axle load distribution of 40:60 (front/rear). The liquid-cooled lithium-ion battery pack consists of 52 modules. Compared to the first e-tron technology platform, the energy capacity of the new 595 kg (1,311.8 lb) battery system was boosted from around 48.6 kWh to 90.3 kWh without requiring any package modifications.

The two electric motors on the rear axle each output 170 kW and 460 N·m (339.3 lb-ft) of torque—i.e., combined torque is a massive 920 N·m (678.6 lb-ft). The R8 e-tron, which weighs just 1,841 kg (4058.7 lb) empty (without driver) has an electronically governed top speed of 250 km/h (155.3 mph). Targeted Torque Vectoring—a need-based distribution of drive power between the rear wheels—gives the car maximum stability and dynamism.

Intelligent energy management and an electromechanical brake system at the rear axle ensure high rates of energy recuperation. The suspension springs consist of glass fiber reinforced polymer (GFRP), and the anti-roll bar is made of CFRP.

The R8 e-tron rides on aerodynamically optimized, high-gloss 19-inch aero wheels that were specially developed for this car. At the front axle, size 225/40R19 tires enable precise steering response. Size 275/40R19 tires transfer the torque of the electric motors to the road. The tires were specially developed for the requirements of an electric supercar, and they combine sporty driving properties with efficient rolling resistance values. Extremely sporty 20-inch wheels of the production R8 are available via the Audi Genuine Accessories program.

The R8 e-tron offers illuminated door sill trims, folding bucket seats and a specially configured Audi virtual cockpit. A heat pump removes waste heat from electrical components for thermal management and for interior climate control—an important efficiency module of the overall concept.

Audi also uses the latest development stage of the R8 e-tron as a high-tech laboratory—it also continues to play an important role in developing electric mobility of the future.

The R8 e-tron will be produced in the small-scale production facility of quattro GmbH at the Audi Neckarsulm site in the Böllinger Höfe.

The battery. The new battery cells are primarily responsible for the new performance and driving range of the Audi R8 e-tron. Audi has systematically adapted its high-voltage battery system to the specific needs of electric cars; the primary focus was on achieving an optimal ratio between power and energy.

In developing the high-voltage battery, Audi followed the principle of maximum flexibility without losing sight of synergies in electrification. The flexible cell module concept allows Audi to be situated for future market developments, while the modular concept also enables Volkswagen Group-wide use across different car models.

The battery operates with 385 volts of nominal voltage. The T-shaped battery system measures 235 cm (92.5 in) long, 136 cm (53.5 in) wide and 70 cm (27.6 in) high, including the junction box on the cross-bar of the “T”. This junction box is responsible for monitoring, switching and transmitting an electrical current of more than 1,200 amperes. The highly complex battery system consists of more than 10,000 individual parts.

The 7,488 cells are packed in 52 modules of 144 cells each. Each module weighs 7.8 kg (17.2 lb). They are arranged on two and five levels (“floors”) in the tunnel battery and in the rear battery. Aluminum plates separate the “floors” from one another while creating the supporting structure for the battery.

Coolant circulates in a cooling system of aluminum shells. In a crash, high-strength floor plates and impact plates redirect the crash forces into the multimaterial ASF (Audi Space Frame) of the R8 e-tron in a defined way.

The 595 kg (1311.8 lb) battery system is joined to the ASF with bolts in the middle tunnel and behind the occupant cell, making it an integral part of the vehicle structure. Its mounting position results in a low center of gravity and an axle load distribution of 40:60 (front/rear), which is ideal for a mid-engine sports car.

The Combo 2 charging interface of the Combined Charging System in the Audi R8 e-tron enables charging with AC or DC electricity. When charging with AC from an industrial electrical outlet with 7.2 kW of charging power, a full charge is reached in just around 12 hours.

Charging with DC electricity shortens the time to 95 minutes at a charging power of 50 kW. Audi is demonstrating charging equipment that can charge this battery system with up to 150 kW of charging power.

For the driver of the R8 e-tron, this means that a driving range of around 150 km (93.2 mi) can be attained after just 15 minutes of charging time. The customer can manage charging remotely as well, using a smartphone on which the customer has installed the relevant Audi connect app.