P3 EV Charging Index: Mercedes EQS gets furthest
The Mercedes EQS is the electric car that gets furthest of them all (266 km) after a fast-charging session of 10 or 20 minutes, outpacing Tesla Model 3 Long Range (221 km), Volkswagen ID.3 (220 km), and the Porsche Taycan (217 km). That is the outcome of the 2021 P3 Charging Index published by eMobility consultancy firm P3 Automotive.
P3 is a German organization that monitors technologies in the fields of mobility, digitalization, and energy. One area of expertise is the charging infrastructure for electric cars, and they take a close look at fast-charging technology in their P3 Charging Index.
P3 starts from the perspective of the EV driver and is mainly based on two parameters. How many kilometers can you really drive (highway included) with one battery charge, and how many kilometers can you recharge in 20 minutes?
Average charge rate
All manufacturers are hammering us with figures, and the DC charging speed increases with every market introduction of a new EV model. P3 investigates whether the cars actually achieve these charging speeds.
Although a car can achieve a (top) charging speed of, say, 200 kWh, it turns out that the average charging speed (measured over a 20-minute charging process) is often significantly lower.
In the attached graph, it is noticeable that the Porsche Taycan, which promises a maximum charging speed of up to 270 kWh, is indeed the fastest of the bunch, but the car does not reach this charging speed during the entire charging process.
With an average of 184 kWh, it is by far the fastest, ahead of the Mercedes EQS, which also peaks at over 200 kWh, but averages 164 kWh. The Audi e-tron 55 shares third place with the Tesla Model 3 at 146 kWh.
The charging speed of a battery depends on several factors. For a start, the temperature is crucial. If it is too low or too high, (quick) charging will not be possible, and the storage speed will drop. Cooling or heating is a solution, but that takes time (and energy).
The second important element is the charge level of the battery. The cells can only be charged quickly when the remaining capacity is between 10 and 80%. This charging window varies from manufacturer to manufacturer. When the battery is empty or almost full, the charging speed is lower.
Voltage also plays a role because an 800 Volt system, such as that of the Porsche Taycan, is fast because resistance (Ampere) is lower under the influence of Ohm’s law. On the other hand, batteries with a larger capacity also charge faster because resistance and temperature rise during charging.
The P3 index is interesting from a technical point of view. It is essential for electric vehicles that often drive long distances in one go (+300 km) and need to recharge during their trip to reach the destination. Due to the limited distances in Belgium, this is less relevant in this country because most EV drivers will mainly charge at home and at their destination.
Moreover, the DC charging capacities that manufacturers make possible today are rarely available. Not all fast chargers deliver the specified charging current because the grid cannot always provide the same amount of current everywhere. When several vehicles charge simultaneously in the same zone, the speed drops as well.
It does not look like this (grid) problem will improve soon. That is why we see EV manufacturers, such as Tesla, investing in brand-specific charging infrastructure. Porsche, too, has plans in this direction.