DECODING ELECTRIC VEHICLE CHARGING MYSTERY
Charging time of an electric vehicle depends on various factors and more often the estimated data provided by car companies only maps ideal-case scenarios
How long does it take to “fill up” an electric car? Well, that depends on the car, and the charger, and how many other cars are plugged into the charger, and how full the battery is to begin with, and the weather matters too. If filling up a gas vehicle is a game of tic-tac-toe, charging an electric vehicle is 3D chess-or a 10-letter version of Wordle.
Mind you, it doesn’t have to be this tricky. For each specific model, car companies have carefully mapped just how much electricity it can accept and how quickly it can generate, assuming a best-case scenario. The resulting plot is called a charge curve. “It shows you the sweet spot of when to plug in,” said Tom Moloughney, who maps charging curves for his YouTube channel, State of Charge.
The x-axis plots how full the battery is on a scale from 0 to 100%; the y-axis records how much electricity the machine is gobbling up at any given time. As the battery gets full, it accepts less electricity and charges more slowly, which is why the line recording the spectrum of charging generally descends.
What this means is that a 20-minute charge when the battery is close to empty generally adds more miles than one when only half of the range has expired — though that can depend on the particular vehicle. The refuelling chart on a Tesla starts relatively high, but drops quickly after just five or 10 minutes, Moloughney explained. Most others step down gradually. Audi and Porsche, meanwhile, have the best charging patterns: “a flat line all the way to 80%”.
The problem is, charging curves are still not published — at least by carmakers. “I think they’re concerned about making their electric vehicles look too complicated,” Moloughney explained. Instead, auto executives try to turn this spectrum of extremely nuanced data into a couple of quick data points, focusing on miles and minutes. Porsche, for example, says its Taycan battery charges from 5% to 80% in 22.5 minutes. Ford Motor, in turn, talks about charging from 15% to 80%. However, Kia says it takes 18 minutes for its EV6 to juice from 10% to 80%.
The carmakers may be handling the heavy math, but without a standard benchmark, comparison shopping is difficult. With electric vehicle ranges improving all the time, the future of the market will be determined in no small part by how quickly and reliably these machines juice up. “It’s not necessarily range anxiety anymore as much as it’s time anxiety,” said Charles Poon, director of electrified systems engineering at Ford Motor.
However, charging curves might give customers unrealistic expectations as they are performed under perfect conditions in a lab with batteries preconditioned to an ideal temperature. Mercedes-Benz Group is hoping the issue is rendered moot, both by vehicles that can travel far on a charge and by a navigation system that automatically calculates optimal refuelling stops given the machine’s charging curve. General Motors is taking a similar approach, assuming the driver’s app and the vehicle’s controls will game the curve for any given trip.
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