intends to use the high-voltage battery ,located centrally in the drive and
literally in the middle of the Audi RS Q e-tron, to set the next milestone in
the world’s toughest rally and prove “Vorsprung durch Technik” in the desert as
battery embodies the heart of the innovative electric drive with energy
converter. “With our drive configuration
in the RS Q e-tron, Audi is a pioneer in the Dakar Rally,” says Lukas Folie,
the high-voltage battery engineer, adding that “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 endurance
Design for unknown requirements
to the Formula E World Championship, which Audi last contested with a battery
electric drive, the standards at the Dakar Rally are different: daily stages of
many hundreds of kilometers, the enormous driving resistance in the soft desert
sand, plus high outside temperatures and a minimum vehicle weight set by the
regulations at two tons are extreme values in motorsport.
is not possible with today’s battery technology to realize an all-electric BEV
off-road vehicle for the Dakar Rally under these conditions,” says Lukas Folie.
The engineering team led by Axel Löffler, Chief Designer of the RS Q e-tron,
therefore had to define basic benchmarks for the overall concept of the vehicle
with electric drive and energy converter without any previous empirical values.
Due to the short project development time, Audi relied on proven cell
technology. The capacity of the high-voltage battery is 52 kWh and is therefore
sufficient for the maximum expected requirements on each leg of the rally. The
weight of the high-voltage battery including the cooling medium is around 370
required energy capacity and performance, as well as control and safety
mechanisms, made Audi resort to proven round cells as the basis of the
high-voltage battery. The battery system is designed in such a way that Audi
Sport drivers Mattias Ekström, Stéphane Peterhansel and Carlos Sainz do not
feel any difference between a new and a used battery.
the rally drivers leave the bivouac in electric drive on the morning of each
stage with a charged high-voltage battery, a highly complex control system
begins. Only a few minutes before the start of the stage do the teams learn any
details about the route at all when the road books are handed out. The Audi RS
Q e-tron with its innovative drive must always be prepared for all conditions
in terms of distances, speeds, difficulty of the terrain and other factors.
engineers and electronic technicians have programmed algorithms to keep the
State of Charge (SoC), i.e. the charge level, within defined ranges depending
on the energy demand. Energy extraction and battery recharging 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 state of
charge drops within a controlled range. The reason: The drive power of the
engine-generator units on the front and rear axles is limited to a maximum of
288 kW in total under the regulations. However, the energy converter can only
provide a maximum charging power of 220 kW. In extreme cases, therefore,
consumption is briefly higher than energy generation. “Something like this is
possible for a limited time,” says Lukas Folie. “But over a longer distance, it
always results in a zero-sum game: We then have to regulate the power
consumption down so that the battery’s state of charge remains within a
corridor. The absolute amount of energy available on board must be sufficient
to cover the day’s leg,” says Folie.
Energy recovery as an important factor
order to realize maximum efficiency, Audi is also relying on a principle in the
desert that has already been used in the Le Mans sports cars and in Formula E:
The RS Q e-tron recovers energy during 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 recuperate the maximum energy. The power flow in this
reverse direction is not subject to the same power limitations as when
accelerating. What sounds so simple requires a complex Intelligent Brake System
(IBS). It combines the hydraulic braking function with the electric
to this targeted design, the RS Q e-tron has an exceptional position in the
starting field. This applies not only to the basic system topology of all
assemblies, but also to the energy control system. Although it has to move a
larger mass due to the regulations, the RS Q e-tron manages with less energy
than the competition. The smaller tank volume for the energy converter
specified in the regulations proves that the rally car with the four rings is
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