– Design for unknown requirements in the Dakar Rally

– Demanding charging process in complex off-road operation

– Intelligent energy management with recuperation when braking

The high-voltage battery is located in the center of the drive and literally in the middle of the Audi RS Q e-tron. It embodies the heart of the innovative electric drive with energy converter. With this, Audi wants to set the next milestone in the toughest rally in the world and also to prove “Vorsprung durch Technik” in the desert.

“With our drive configuration in the RS Q e-tron, Audi is a pioneer in the Dakar Rally,” says Lukas Folie, high-voltage battery engineer. “Defining the challenges for this type of competition was very demanding. There are simply no empirical values ​​in motorsport for such a concept and for this type of long-distance competition. “

Longevity and high energy density

The required energy capacity and power as well as control and safety mechanisms let Audi fall back on tried and tested round cells as the basis of the high-voltage battery. The battery system is designed so that Audi Sport Driver Mattias Ekström, Stephane Peterhansel and Carlos Sainz Don’t feel the difference between a new and a used battery.

Demanding charging in the area

When the rally drivers leave the electric bivouac with a charged high-voltage battery on the morning of each stage, a highly complex control system begins. Only a few minutes before the start of the stage do the teams find out details about the route when the road books are issued. The Audi RS Q e-tron with its innovative drive must always be prepared for all conditions in terms of distances, speeds, terrain difficulties and other factors. The engineers and electronics technicians have programmed algorithms to keep the State of Charge (SoC), i.e. the state of charge, in defined ranges depending on the energy requirement. Energy consumption and battery charging are always in balance over defined distances. If, for example, a difficult dune passage with high driving resistance requires maximum energy for a short time, the charge level drops to a controlled range. The reason: According to the regulations, the drive power of the motor-generator units on the front and rear axles is limited to a maximum of 288 kW. However, the energy converter can only provide a maximum charging power of 220 kW. In extreme cases, the consumption is therefore briefly higher than the energy generation. “Something like this is possible for a limited time,” says Lukas Folie. “But over a longer distance, there is always a zero-sum game: We then have to regulate the power consumption down so that the state of charge of the battery remains within a corridor. The absolute amount of energy available on board must be sufficient to cover the leg of the day. “

Energy recovery as an important factor

In order to achieve maximum efficiency, Audi also uses a principle in the desert that was already used in Le Mans sports cars and in Formula E.: The RS Q e-tron recovers energy when braking. The MGU units on the front and rear axles can convert the rotational movement of the wheels into electrical energy. The aim is to regain the maximum amount of energy. The power flow in this reverse direction is not subject to the same power limits as when accelerating. What sounds so simple requires a complex Intelligent Brake System (IBS). It combines the hydraulic braking function with the electric regenerative brake.

Efficiently on the go

Thanks to this targeted construction, the RS Q e-tron occupies an exceptional position in the starting field. This applies not only to the basic system topology of all assemblies, but also to the power control system. Although it has to move a larger mass due to the regulations, the RS Q e-tron uses less energy than the competition. The smaller tank volume for the energy converter stipulated in the regulations proves that the rally car with the four rings is very efficient.

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