Extended e-powering

The Audi e-tron quattro is powered only by electricity

Power is transmitted to the front and rear axles by two-stage planetary gear units via differentials. Two motors on the axles with maximum outputs of 265 kW and 126 kW deliver a torque of 314 Nm on the rear axle alone. What more could you ask for nowadays?

But the weightiest feature first: Yes, it tips the scales at a mere 2,565 kilograms empty! But this is not entirely unusual for an all-electric vehicle, especially when it comes in this format and promises a range of more than 400 kilometers. Even at a maximum speed of 200 km/h at times. And, moreover, it achieves half of this inside just 6.6 seconds. 

With these specs, it becomes clear that the Audi e-tron quattro has set itself the goal of downscaling the well-known disadvantages of battery-powered mobility – i.e. primarily the limitation of range – to a minimum and allowing its owners an electric vehicle compatible with everyday demands.

Double battery power

The 4.90 meter long SUV is bi-batteried, with a main battery in the vehicle floor and an extra one under the rear seat. The boxes for the latter are manufactured in Neckarsulm by KS HUAYU AluTech GmbH where development of the battery packs began as early as December 2016. This was fresh terrain also for KS HUAYU, but still one in which the then classic caster of engine blocks, cylinder heads and its first structural components was able to inject a full range of competences.

The boxes have a wall thickness of a mere 2 millimeters

And this fitted the bill according to Jörg Völler, Technical Customer Consultant and Project Manager at KS HUAYU for the development of the new battery boxes – the latter had to be done in just 18 months: “We cast parts here that are 1,350 millimeters long, 550 millimeters wide and 100 millimeters high, with extremely thin wall thicknesses of only 2 millimeters. That was also a great challenge for us.” It involved a die-casting process that first has to be mastered and requires many years of experience with aluminum. This is especially important because one essential condition has the highest priority for the battery boxes: the castings must be absolutely leak-proof. In addition, Völler explains, “parts could get distorted in the manufacturing process due to the thin walls. For this reason, all finish-cast battery boxes first undergo a straightening process, during which they are adjusted if necessary. Only then do they receive a cathodic dip coating from an outside contractor. On the one hand, this protects against contact corrosion. On the other hand, in the event of any ignition, the coating material (as used in defence technology) displaces the oxygen within the battery.

Faraday cage principle

After this “excursion”, the boxes return to KS HUAYU. But before they go to the customer, they have to pass through another process. Völler explains why: “Together with its cover, the battery box forms a kind of Faraday cage. So the contact between the cover and the box must be 100 percent tight, which, in turn, would prevent dip painting.” 

For this reason, the trays are subjected to a clean laser process in which the contact surfaces to the later deep-drawn cover are re-exposed, thus ensuring the conductive connection between the two parts and external protection against the high voltages.  But that’s not the end of the story, because the production of the battery boxes required an investment of 35 million euros in a new shop and in modern machines with a corresponding closing force, which KS HUAYU put into operation last year. This was mainly necessary due to additional orders for components beyond the combustion engine and including mounts for shock absorbers and suspension struts as well as crossbeams from aluminum.

After completion, the battery boxes are shipped to the Audi plant in Brussels, where the battery cells are fitted and the entire vehicle is assembled from the C-BEV modular system. However, the Audi developers in Neckarsulm were in charge of developing the battery boxes for the customer. Völler: “The short distances here in Neckarsulm helped us a lot in the development work”. Audi also gives a battery warranty of 100,000 kilometers or 8 years for its SUV, which costs a good 80,000 euros, and thus ensures many years of trouble-free e-motoring with the e-tron.