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LA show: Audi reveals A7 Sportback h-tron

Ready to go: Audi claims to have mastered fuel cell technology with its A7 h-tron concept, which makes few compromises in the quest for outstanding environmental and sports-luxury performance.

Audi’s unique high-performance quattro fuel cell prototype uses plug-in hybrid tech


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20 Nov 2014

AUDI revealed a unique hydrogen fuel cell electric vehicle based on its A7 Sportback at the Los Angeles auto show this week, claiming to have mastered fuel cell technology and to be now ready to enter production “as soon as the market and infrastructure are ready”.

A driveable technology demonstrator rather than a mere concept car, the A7 Sportback h-tron quattro was shown in LA as one of two new hydrogen-powered prototypes from the Volkswagen Group, with the Golf Sportwagon HyMotion prototype also making its world debut at the show.

The fuel cell system in both vehicles was developed in-house by the European auto giant and has a unique combination of both FCEV and plug-in hybrid, although the Audi has lashings of luxury, loads of power and quattro permanent four-wheel drive thrown in to prove that it will not compromise its core attributes in the name of zero-emissions motoring.

The upshot is a 1950kg vehicle that can produce 170kW of power and 540Nm of torque from two electric motors on board, accelerating from 0-100km/h in 7.9 seconds on its way to a top speed of 180km/h.

It can reportedly cover more than 500km before its hydrogen tanks need refuelling, with its lightweight plastic exhaust emitting “nothing more than a few drops of water”.

The primary energy source, the fuel cell stack, is under the bonnet in place of the conventional internal combustion engine and comprises more than 300 individual cells, each a polymer membrane with a platinum-based catalyst on either side.

Each cell’s output ranges from 0.6 to 0.8 volts, with the entire system operating in the voltage range of 230 to 360 volts.

Four hydrogen tanks with an outer skin made from carbon-fibre reinforced polymer are under the vehicle ahead of the rear axle and able to store about 5kg of hydrogen at a pressure of 700bar.

Audi has shown hydrogen test cars before with the A2 H2 and Q5 HFC, but the A7 h-tron marks a significant departure with the integration of the A3 e-tron plug-in hybrid’s 8.8kWh lithium-ion battery under the boot, acting as a performance booster.

Recharged via a cable and socket, or through regenerative braking, the battery is said to improve acceleration and can extend the vehicle’s driving range by up to 50km.

As the battery operates at a different voltage level to the fuel cell, a DC converter is included.

Four-wheel drive is provided by the two electric motors, one at each axle, using electronic control – there are no mechanical connections. Each motor has an output of 85kW, or as much as 114kW if the voltage is temporarily raised, while peak torque is 270Nm per motor.

In presenting the prototype in LA, Audi’s technical development chief Ulrich Hackenberg described the A7 h-tron as “a genuine Audi – at once sporty and efficient” and a vehicle that was conceived as an “e-quattro” with its two electric motors driving all four wheels.

“The h-tron concept car shows that we have also mastered fuel cell technology,” he said.

“We are in a position to launch the production process as soon as the market and infrastructure are ready.”

Audi says that in fuel cell mode, the vehicle needs only about 1kg of hydrogen to cover 100km – an energy content equivalent to that of 3.7 litres of petrol, based on the NEDC cycle.

It also claims the fuel cell reaches its maximum output within one second at full load – “a more dynamic response than a combustion engine because the entire drive system involves only a few mechanical components”.

Just as with the exterior, no great changes have been made to the cabin in the transition from conventional to h-tron powertrain, although it does have a few unique features.

A power meter takes the place of the tacho in the instrument cluster, informing the driver of the momentary power flow. The outer sections show the fuel level in the hydrogen tank and the level of battery charge, while graphics on the MMI monitor visualise the energy flow.

The vehicle can be driven solely on battery power through the use of an EV button, while switching the transmission mode from D to S increases the level of energy recovery when braking – a function designed to be employed during spirited driving.

The A7 Sportback h-tron was shown alongside the Prologue concept at the LA show, a flagship coupe that represents a new design direction and model niche for the luxury brand.

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