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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. (Earlier post.) 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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

Comments

Davemart

150kw based on the CCS standard blows away notions that only the Tesla supercharger will do.

The 150wh/kg at the pack level of this is also in the same ball park as Tesla's Panasonic batteries.

electric-car-insider.com

Yes, if they will build them in volume, and roll out a few thousand of those 150wK charging stations all over the world, Tesla may have to look in the rear view mirror. It appears though, that Tesla has at least a 10 year head start. Unfortunate that the R8 is hand built, special order only, apparently will not be offered in the US.

All hope is not lost, looking forward to driving the A3 e-tron this fall.

Davemart

@eci:

What in the world are you talking about now?

It is taking six months to roll out a fast charging network appropriate to the vehicles it intend to serve across a medium sized country, about one and a half times as big as California.

The install will have taken into account possible future upgrades, so that it is relatively easy to go to 100kw or 150kw by feeding new cables into blank pipes and so on.

So that becomes ten years lead in the wonderful world of Tesla?

HarveyD

Quick charge (evolution) charging RE and/or Grid connected stations are not a real problem. It can be done very quickly. France is doing it by end of 2015.

Improved 2X batteries at $150/kWh are around the corner and will be on the market place by 2017/2018 or so followed by 3X to 4X batteries at under $100/kWh by 2020 or.

Extended range BEVs of all sizes, speed and cost will soon bloom in great quantities.

ICEVs will have to improve their performance by 6X or so, like the demonstration Ford RE (VW) Diesel unit, capable of a cross country (USA) trip on a single tank of RE diesel fuels.

Lad

This is a huge heavy battery with a cockpit built around it. A double density battery would improve it in all areas immensely.

HarveyD

Yes, and they are coming soon.

electric-car-insider.com

DM> ...possible future upgrades...

I applaud Audi for making progress and announcing their intent to build and sell the R8 e-tron to those very few lucky Europeans who are able to get their hands on one. Impressed enough to put it on the cover of Electric Car Insider magazine in the current issue. But it is really a bit of a tease, and we said so in the profile.

Audi does a better job with EV press releases than any other company. Alluring, tantalizing. But mostly only in your dreams.

Tesla, on the other hand, is building both cars and the network at an astonishing clip for a new market entrant. Not maybe sometime in the future. Now, today.

And it will apparently be a decade or more until anyone else delivers an equivalent capability.

James McLaughlin

A low volume fast two seat EV with good range? Looks like they caught up to and passed the Tesla Roadster. This is probably more comfortable and has faster charging (at least potentially). Nice. I expect they will learn something useful from the effort. There will not be enough volume to affect the market much though. Still, good effort.

SJC

The R8e has been on and off over the years, I am glad they finally decided to build them even if this is nothing more than corporate image.

ai_vin

@ James

Actually, Tesla Motors' CEO Elon Musk has announced the Roadster will be eligible for a retrofit package upgrade. It will allow buyers of his first car to get a range of 400 miles.

http://www.cnet.com/news/tesla-roadster-getting-battery-upgrade-for-400-mile-range/

HarveyD

TESLA is reading the future correctly with extended range (400+ miles) BEVs and very quick charging facilities (150+ KW). Wouldn't be surprised to 200 KW charging units on many highways by 2020 or so.

Of course, most home charging units will be much smaller, 8.8 KW units would do the job for overnight charging.

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