Anyone who regularly drives longer distances in an e-car knows that maximum charging power is just one of many factors to ensure the fastest possible charging. Ultimately, what really counts is the “recharged range”. A recent ranking provides an insight into this.
Charging is not the same as fueling – that much is clear. But what precisely is the difference between charging a battery and filling a tank with fuel? What are the technical obstacles to fast charging, and which electric cars have best mastered the discipline of fast charging? A recent ranking by the engineering services consultancy P3 gives the low-down on this. The “P3 Charging Index” was first published in 2019, and has now been updated for 2021. The ranking is notable for its particularly realistic comparison, since not only does it list maximum charging power, but it also calculates the recharged ranges (i.e. actual ranges) of various electric cars. In this key ratio, the ranking establishes the power charge delivered within a specified time range as a proportion of the car’s average real-use consumption.
In doing this, the ranking makes a series of assumptions in order to map actual experience in as realistic and user-oriented a manner as possible. Hence the specified charging time was set as 20 minutes, which is considered a viable time-frame for fast charging – the “standardized coffee break”, so to speak. To measure charging performance within these 20 minutes, a charging curve was drawn up for each of the twelve electric car models taking part. The charging curve starts at ten percent state of charge (SoC) and ends at 80 percent. Two values are calculated from this charging curve: The average charging power over the full charging curve (10 - 80 percent SoC), and the recharged power within the first 20 minutes (starting at 10 percent SoC). The recharged power is then converted into the actual range (the recharge range), using the car’s real-use consumption (according to the ADAC Ecotest), and this forms the basis of the Index.However, average charging power is not a component of the Index, but is provided as additional information.
To measure the charging curves, the twelve cars taking part were connected to commercial fast chargers that enable a maximum charging power of 350 kW. However, the vehicles were often only able to maintain their maximum charging power for just a short time. The reason for this is that fast charging represents a high load on the cars, and it heats up the batteries more and more as the charging time extends. Key to a fast charging process is therefore, above all, the battery’s ability to accommodate that load, using suitable management and cooling systems. How well this is achieved can be seen from the charging curves. The subsequent ranking indicates the actual range, first after ten minutes and then after the full 20 minutes, to map how charging power changes over time.
The best-ranking car in the Charging Index 2021 is the Mercedes-Benz EQS. The fully-electric S-Class from the Stuttgart-based manufacturer achieves an actual range of 266 kilometers in the indicative 20 minutes. One reason for this good result is its above-average sized battery, with a range of close on 770 kilometers. It makes it easier for the car to maintain consistently high charging power over the 20 minutes. As a result, the EQS achieves a peak charging power of over 200 kW and an average value of 164 kW (measured from 10 to 80 percent SoC). At the end of the charging procedure, the battery’s SoC was 62 percent. Its top ranking sees the EQS demonstrating it is particularly suitable for long-distance travel.
With 221 actually-charged kilometers, second place in the Charging Index goes to the Tesla Model 3 LR. This mid-class car scores well for its maximum charging power of around 250 kW, although over time this steadily drops away and ultimately results in an average figure of 146 kW. This curve means that at the ten-minute mark the Model 3 was still top-ranking, but after the full 20 minutes it has been overtaken by the Mercedes EQS in first place. At the end of the 20-minute charging procedure, the SoC had climbed from ten to just on 70 percent. So that coffee break has paid off!
It was close, but just behind the Model 3 comes the ID.3 , with an actually-charged range of 220 kilometers. In its largest battery option, the electric car compact offers a battery capacity of 550 kilometers (WLTP) and a maximum charging power of 125 kW. Over the full charging curve (10 to 80 percent SoC), the car achieves an average figure of 102 kW. That’s a good score, which is only topped by the ID.3’s particularly modest consumption. According to the ADAC Ecotest, the ID.3 is actually the best-performing of all the vehicles tested, in terms of power consumption.
In 2019, the Porsche Taycan ranked as number one, and this year it comes out in fourth place, with an actually-charged range of 217 kilometers. If charging power alone is taken into consideration, however, the Taycan is still the best-rated vehicle: Its peak charging power of 270 kW and average power of 184 kW remain unbeaten. The reason this is only good enough for fourth place in the P3 Charging Index is that this electric sports car naturally goes into the race with high consumption figures. Compared to the other models, this reduces the actually-charged range. After 20 minutes, the Taycan’s SoC is 77 percent.
With 197 kilometers for actually-charged range and an Index score of 0.66, the Tesla Model S takes fifth place in the fast charging ranking. Particularly noteworthy on this electric sedan is that the Model S charges most consistently, with 99 kilometers in the first ten minutes and 98 kilometers in the second ten. That’s testimony to the vehicle’s outstanding charge management, which takes its 100-kWh battery to a 57 percent SoC over the time.
The other cars taking part in the ranking were similarly able to demonstrate strong performance. Places six to twelve went to the following models: Audi e-tron 55 (187 kilometers), Tesla Model X 100D (185 kilometers), Mercedes EQA 250 (180 kilometers), BMW iX3 (173 kilometers), Volkswagen ID.4 Pro (171 kilometers), Polestar 2 LR (163 kilometers) and Ford Mach E LR (155 kilometers).
(Stage photo: © Ionity)
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