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Published on May 17th, 2019 | by Guest Contributor

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Correcting Audi: Tesla Model 3 Charges Over 2 Times Faster Than Audi e-tron

May 17th, 2019 by  


The article was written by Simon Barke and Myles Clark. They each hold a PhD in physics, work for an international space mission at the University of Florida, and understand scientific data quite well.

Matthew Mostafaei, Audi’s manager for e-tron, presented data taken from Twitter during the New York Auto Show without naming the source. (That’s plagiarism.) The data was misrepresented by plotting it on a different axis. (That’s a falsification.) He then used the data to show the e-tron’s charging superiority over the Model 3, when it actually proves the opposite. (That’s deception.) You may call this good marketing. I call it a brazen lie. At best, it is a highly misleading accident.

A chart presented by Audi’s manager for e-tron and connected vehicles in the US, Matthew Mostafaei, made the rounds this week. During a New York International Auto Show presentation, he pointed out how much longer Audi’s new all-electric “e-tron” SUV can sustain a 150 kW charge rate. The point of the chart: in many situations, the e-tron charges faster at a 150 kW charger than a Tesla at the upcoming 250 kW “Supercharger V3.” And the faster you charge, the quicker you arrive. Right? No, not quite…

There is a lot of confusion about electric vehicles. Different test cycles, range, state of charge, efficiency, charging power, and charging rate. This lack of general knowledge helps companies make unsubstantiated claims about their cars.

I got on the phone with Mark Dahncke (Director, Product/Technology/Motorsports Communications of Audi USA) about this. He confirmed the source of the data and admitted that Audi never contacted or credited the original author. He further regretted that Audi (accidentally) falsified the underlying data. Although he was now denying that the presented chart implies that the e-tron can charge faster, he was still defending Audi’s basic claim that a high charging power helps you reach your destination faster. Oversimplified statements like these are not only purposefully misleading. They also add to general EV confusion, which is bad for everyone.

Let’s set the record straight, try to understand what Audi did, and find out what the data really shows. Below is the slide Audi showed during the New York Auto Show presentation. The chart shows the charging power (20 to 250 kW) of different electric vehicles over battery state of charge (0 to 100%). The first indication that something is terribly fishy here is the fact that the unspecified Tesla at a third-generation Supercharger starts charging at negative 1%. (The black line and red arrow/text was added by me.)

Audi got the data from Twitter — and did not know how to read it.

When I confronted Audi with the charges of plagiarism, I was told they used an image published by Electrek. However, Electrek is not the author of the data and instead itself names the original Twitter source. It was published 2 months ago by user “@privater” on Twitter (“u/privaterbok” on Reddit).

On reddit here.

Audi’s mysterious charging profile is a perfect match. What is striking, however, is that the data posted on Twitter was plotted on a non-equidistant horizontal axis. Notice that 28%, 30%, 40%, and 44% are spaced by the same distance on the chart while being different by 2%, 10%, and 4%, respectively. Audi blatantly ignored that, simply copied and pasted the v3 trace onto its traditional, equidistant axis, and stretched it arbitrarily so that it somehow worked with the rest of Audi’s chart. The company never cared to check the underlying data. No wonder they got confused to the point that their version now starts with the car in a negative state of charge!

Luckily, u/privaterbok used Reddit to post the original data in a spreadsheet. I managed to create a corrected version of Audi’s chart that also includes a new charging profile for the upgraded 150 kW Tesla Supercharger V2.

It is important to note that the 250 kW Supercharger system is still in a testing phase and further improvements are likely. Both Tesla charging profiles do not include any automated battery preheating, which will increase charge powers at low charge states. So, the Tesla charging profiles shown here can be seen as conservative. Anyhow, now that we have corrected data to work with, we can answer the question of what this data is actually telling us.

In its current form, it is purposefully misleading. Don’t get me wrong — it is very impressive that the e-tron can sustain a higher charging power at a higher battery state of charge. But does this help you get anywhere faster? Not without the range and efficiency to back it up it won’t…

Charging power is not charging speed!

First of all, we have to adjust the horizontal axis. Who cares about battery percentage? The important information for the driver is how far they can go before they need to fill up. The battery of a low-range vehicle does not get me anywhere, no matter if it is fully charged or not. For the Audi, a 100% state of charge corresponds to 204 miles (EPA test cycle). The Tesla data Audi copied from Twitter was measured from a Model 3 Long Range, hence I will correctly use 325 miles for a 100% state of charge. The chart above highlights the 40 mile and 200 mile range equivalents for the e-tron and the Tesla, so we can rescale the traces accordingly and plot the charging power over electric vehicle range.

This version of the chart is slightly less misleading, but we still have another step before this is a real apples-to-apples comparison. That step is to take into account how fast the vehicles actually charge in units that are more relevant in the real world. For that, we need to adjust the vertical axis to reflect charging speed (charge rate in miles per hour). This metric not only depends on the charging power but also on the efficiency of the vehicle. The more efficient a vehicle is, the more range you add for any given charging power.

The Model 3 Long Range maxes out at a ludicrous 1000 miles per hour at 250 kW charging power. This translates to close to 600 miles per hour at the 150 kW level. If you do the math, these values include a roughly 8% loss (mainly due to heat). If we assume the same 8% loss for charging the e-tron, the picture looks very different. Audi’s entry in the electric vehicle market peaks at just above 300 miles of range added per hour at the charger due to its inferior efficiency: it needs to charge a much larger battery which provides significantly less range than the Model 3’s much smaller battery.


Finally, we can directly compare the speed at which the two cars can charge. The area below the charging profile is directly related to the time it takes to add drivable range to the car. As an example, I picked a realistic remaining range of 40 miles before we begin charging. We then charge both cars to 200 miles (since the Audi can’t get beyond 204 miles). You can see in the chart above in the highlighted area between 40 and 200 miles: the larger this area, the faster the charge process will be to add 160 miles of range. So, in reality, the Audi e-tron charges way slower than the Tesla Model 3 even at the older generation Supercharger.

How long does it take to add 160 miles of range?

@privater, the Twitter user who published the original data, also posted the charts for range vs time while charging.

From these charts, we know for certain that it took 15 minutes to charge from 40 to 200 miles on the third-generation Supercharger. This would translate to roughly 21 minutes when charging the same car at a V2 Supercharger. And the e-tron? Well, if our charge rate estimates are correct, it would take 36 minutes for the e-tron to add 160 miles of range.

Can this be true? Turns out, our estimate is spot on. User “Elbil24” published a video on YouTube charging the e-tron from 1% to 99% at a 175 kW rapid charger. For this charging session, it took exactly 36.7 minutes to charge from 20% to 98% (which corresponds to 160 miles on the EPA test cycle).

So let’s go back to Audi’s headline: “quick to charge = quick to arrive.” This is true, but Audi forgot to mention that the e-tron’s real-world charging is discouragingly slow.

Tl;dr

Here is what you should take away from this article: do not trust anything published by the Volkswagen Group. After all the coverups from the past few years, it comes as no surprise that Audi keeps deceiving the public with falsified data and twisted arguments. Some companies never learn. I just hope customers finally will. 
 
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