Audi is committed to mastering all stages of production for electric mobility and to optimizing these processes to meet the particular expectations of the customers. An “off-the-shelf” battery is therefore out of the question for the brand with the four rings. The Vorsprung that Audi represents can only be achieved in the future with proprietary expertise. It therefore became clear during at an early point in the development of the Audi e-tron that the comprehensive approach had to also include an in-house battery assembly facility.
Using battery systems the way Audi does requires aligning stringent and in some cases contradictory requirements. Agile road performance and enthralling handling require a lightweight, compact construction. At the same time, the battery should deliver as much energy as possible and thousands of charging sessions should function properly with no loss of power output. Efficient cooling is every bit a must as maximum safety of the batteries and their connections.
Expertise from other Audi locations is also channeled into battery assembly in the production network. Parts of the battery cover are sourced from Audi Hungaria’s Győr plant and parts of the battery housing from Neckarsulm, for example. New production technologies were developed specifically for the manufacture of the batteries, such as automated setting of the cell modules using dies allowing precision joining of modules in the compact housing. The individual elements are pressed and bolted to make optimal use of the space, to ensure the load-bearing function of the housing and to make the structure particularly safe.
Production employees have also performed pioneering work in these process steps, too. For example, the electrical connections for the modules are now flexible instead of rigid. The experts from production succeeded in completely automating this highly complex process. A patent application has been submitted for the process.
The Audi e-tron has an aluminum battery housing that is delivered to the assembly line from the body shop. There it is precisely and tightly packed with modules. In the Audi e-tron, there is no cooling system and thus no coolant inside the housing. Instead, a gap filler conducts the waste heat from the cells evenly into the cooling system, which is bonded to outside of the battery housing. This thermally conductive gel also prevents air inclusions, thus guaranteeing full contact with every surface. This construction is a particularly demanding task for production, as there is nothing else like it in the industry. The Audi specialists accomplish this with the largest bond in terms of surface area anywhere in the car.
Electric contacting is the step in which the cell modules are connected to one another. The developers designed a connection with two bolts per module pole to achieve outstanding contact resistance. This means extremely low heat-related energy losses and the maximum flow of current to where it is needed – the electric motors of the Audi e-tron.
After contacting, the voltage level in the system is nearly 400 volts. All employees are therefore appropriately qualified for working with high-voltage technology. Robots mount the cell modules in two layers, one atop the other. The employees then equip the units with the proper wiring and seal the housing. Each battery then undergoes a comprehensive test cycle in two test units. The complete unit is now ready to be precisely installed in the floor assembly of the Audi e-tron. An automated guided vehicle delivers the battery just in time directly to the line.
The equipment, data and prices specified in this document refer to the model range offered in Germany. Subject to change without notice; errors and omissions excepted.