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Second life for used car batteries

Audi is testing factory vehicles powered by lithium-ion batteries at its main factory in Ingolstadt. Like all car builders, Audi is required by law to take back energy carriers after their use in cars. Because they still have a large amount of original loading capacity, an interdisciplinary project team is now investigating how the batteries of, for example, the test vehicles of the Audi e-tron or those of hybrid models such as the Audi A3 e-tron and Audi Q7 e-tron can be considerably longer used. A number of other benefits have already come to light during the test phase.
Until now, factory vehicles such as forklift trucks and tractors at the Audi sites have been powered by lead-acid batteries. When their batteries are empty, employees remove the battery packs that can weigh up to two tons from the vehicles and connect them to a charging station for a few hours. Lithium-ion batteries can, however, be charged directly at the place where the vehicles are parked during standby time or in between shifts, for example. This saves time and eliminates the high manual effort required to move the batteries. Audi would save millions if it had its entire fleet of factory vehicles switched to lithium-ion batteries at the 16 production sites worldwide.

“Manufacturing a lithium-ion battery is accompanied by high energy consumption and valuable raw materials that must be used in the best possible way,” says Peter Kössler, member of the board of directors for production and logistics at AUDI AG. “For us, a sustainable strategy for electric mobility also means a meaningful concept for second-hand use of energy carriers.” The remaining charge capacity of a lithium-ion battery after use in a car is more than sufficient for the requirements of transport vehicles. As a result of this use, their driving capacities actually improve considerably: they can keep their speed constant, even on slopes (factory vehicles powered by lead-acid batteries cannot). In addition, regular loading during breaks prevents downtime during working hours.

The battery of an Audi e-tron, for example, consists of 36 individual battery modules and is placed under the passenger cell between the axles in the form of a flat wide block. After batteries have been taken back, the project team checks each individual module in function of its further use. Then 24 modules are installed in each new battery drawer. It has the same dimensions and weight as the previous lead-acid batteries of the factory vehicles. This way, the company can continue to use all those vehicles without major investments. In the future, specialized employees could take over the assembly of second-hand batteries in the company’s own battery center.

The project team of the production, logistics, and development departments have been working for two years on the second-hand use of used battery modules. After the first tests were successful, they’re now testing the first converted factory vehicles in daily production. This progressive project is one of many that demonstrates Audi’s commitment to the meaningful and efficient further use of batteries from electric cars. It is also conceivable that used battery modules could be used in mobile charging containers for electric vehicles or in stationary energy storage systems. Audi also develops recycling concepts: at the end of the battery life cycle, valuable parts of it get a second life in other products and are thus reused.

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