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Audi deliberately does not rely on the highest energy density and maximum range for its electric cars. Fast recharging is much more important for the customer in everyday life. But this requires quite a bit of know-how from the developers.
Probably not a word falls in the haze of the Electromobility as common as this: reach. It's usually the first question people ask when you show them an electric car. "How far does it go?" The focus is not on performance and acceleration, as was once the case with the combustion engine, but solely on the range. For newcomers, it can even become the decisive selling point.
Is range still that important?
At Audi, range is far from everything. The mileage information is often a nice marketing tool, according to the motto "The bigger the number, the better the car", but later in everyday life very different things often count. Especially since the charging infrastructure is improving every day and range is becoming less and less important.
But if the empty battery forces you to go to the charging station on a longer tour, you usually want to get away from there quickly. Coffee & Go. Nothing is more annoying when it feels like it takes an eternity until the battery is full enough to reach your desired destination stress-free.
Battery size depends on the car
Audi has therefore made charging convenience and charging performance a top priority. But the developers are faced with a conflict of goals. Car dimensions usually dictate a specific battery size. Of course, you want to pack as much energy into this as possible. "But we also want to be able to recharge the battery as quickly as possible," says Dr. Bernhard Rieger, who works in cell development at Audi in Gaimersheim. "The greater the energy density, the longer it takes to charge," says Rieger.
He and his team therefore have to delve deep into the cell structure of the battery and precisely analyze the behavior of the lithium ions during charging and discharging. Where do they deposit ions first? Are they blocking the way for other ions? Is there a risk of overcharging as a result? If this happens, the cells age faster and the capacity decreases. "There is an optimum of energy density and energy that can be recharged," says cell expert Rieger. Anyone who finds this “sweet spot” can give the customer the best charging package to take with them.
With its electric models, Audi has come pretty close to the best point. Under ideal conditions, the cells of the 93 kWh battery in the e-tron GT fill up from five to 270 percent in just 23 minutes with an output of up to 80 kW. A charging curve that runs as horizontally as possible for the first 20 to 25 minutes and only then gradually decreases is generally regarded as optimal. The Audi e-tron 55 is currently very good at this art. Although the SUV does not have an 800-volt architecture like the GT, but only has a 400-volt system and can therefore only be charged with a maximum of 150 kW, the battery cells can handle almost the full charging power (140 kW) over the first 25 minutes.
The battery is 80 percent full after half an hour and completely full after 45 minutes. This charging behavior on DC columns is considered a benchmark in the industry.
There will be more need
Audi also wants to set standards with its charging lounges (charging hubs), intended for customers who do not have their own wall box but still want to drive an electric car. Today the proportion is 20 percent. Forecasts show that demand will triple over the next five years. "So we have to get started now," says strategy project manager Ewald Kremlin. The first of these specially designed charging buildings is in Nuremberg, a pilot facility that Audi says has been very well received. "We hit the customer's nerves," says Kremlin, "over 60 percent are returning." The e-cars can be charged at six stations using HPC (High Performance Charging) columns. Audi drivers can even pre-reserve these via their mobile phone app.
Kept simple
The lounge building is designed not to encroach on the subsoil. "We could completely dismantle it again within two weeks," says Kremlin. An extra strong power supply for the city was also deliberately avoided. Civil engineering measures were taboo. Audi simply uses the local low-voltage network, in this case it is a 200 kW cable. Another 760 kW charging capacity comes from a storage unit on the ground floor of the lounge. It is also powered by solar cells on the roof. The battery pack consists of 26 so-called “second-life batteries” that come from Audi test and prototype vehicles. Anyone who now thinks that the contingent of these vehicles will soon be exhausted will simply reply to Ewald Kremlin: “Audi has more test vehicles in circulation than Lamborghini has produced production cars.”
Nuremberg is the beginning. An Audi charging hub is about to open in Zurich. Then it's Salzburg and Berlin's turn. By the end of 2024, eleven lounges are to be added in Germany, always close to the city. And you don't necessarily have to be the owner of an Audi to supply your e-car with energy here. The only difference: Access to the lounge is denied to drivers of other makes. You stay in the room in front of it. At least the coffee machine is there.
