Unlike Toyota's FCV, the A7 h-tron is all-wheel drive and noticeably more complex in the way power is produced or delivered. The familiar body of the 2014 four-door coupe has been stuffed with no less than four different tanks with carbon fiber shells that hold hydrogen. It also comes with plug-in hybrid technology borrowed form the much smaller A3 e-tron.
The hydrogen fuel cellIt was in spring that we learned Audi was working on its own fuel cell system. The stack is installed under the large bonnet of the A7 and includes 300 individual cells featuring a polymer membrane that has a platinum catalyst coating.
Here's how the hydrogen is used to power the A7. From the tanks, hydrogen is supplied to the anode of the fuel cells where it is broken down into protons and electrons. The protons go though the membrane to the cathode where oxygen is present from air that's been forced in by a sort of turbocharger. Together, they make water vapor. Each cell is then left with the a stream of electrons arriving at the pace of 0.6 to 0.8 volts. Together, the 300 cells deliver a voltage range of 230 to 360 volts.
Because it only has to deal with water vapors and not super-hot exhaust gasses, the exhaust system is not made from metal, but plastic, which we think is pretty cool.
Audi says that the A7 h-tron concept requires a around 1
g (2.2 lbs) or 3.7 liters of hydrogen for each 62 miles (100 km). The electrical power is used by all four wheels and delivered in a way that Audi says is very similar in feel to a normal quattro system. If the tanks are full, the hydrogen is supposed to last for around 310.7 miles (500 km).
The plug-in hybrid side of the A7The fuel cell works in combination with a 8.8 kWh lithium-ion battery pack sourced from the A3 Sportback e-tron installed beneath the trunk and granting 31.1 miles (50 km) of electric range. It's recharged whenever the regenerative braking system is activated or as a conventional PHEV. Using a normal power socket, the battery is full in four hours. Unless we're mistaken, the A7 hasn't been available with e-tron tech.
It's the electric motors, not the fuel cell, that drive the A7. So how much power do they actually have? There's two of them, one for the back axle and one for the front one. Both are rated at 85 kW or 114 kW when "overboost" is activated. The combined output is said to be 228 hp (230 PS or 170 kW) and 540 Nm (398 lb-ft), similar to a 3.0 TDI. Despite weighing 1,950 kg (4,299 lbs), the A7 h-tron quattro concept is said to accelerate to 62 mph (100 km/h) in 7.9 seconds before hitting a top speed of 111.8 mph (180 km/h).