Why Doesn't the Jaguar I-Pace Go As Far As It Should on a Charge? Last week, Jaguar finally received the EPA fuel economy rating for its I-Pace electric crossover, and it probably wasn't what JLR was hoping for. According to the feds, the curvy ride is good for 234 miles of electric driving—a number that’s a few clicks shy of the 240-mile estimate the company had suggested would be the case. That’s disappointing, of course, but not so far off the mark that potential owners should feel particularly cheated. On the other hand, when your main competitor is Tesla—whose closest parallel to the F-Pace is the Model X 75D, which has a smaller battery and weighs more, yet offers similar range—and you have Mercedes, Audi, and BMW nipping at your heels with their own new or forthcoming electric SUVs, every mile counts. (It didn’t help that the difference looks bigger than it is, with the drop taking it from the 240s to the 230s.) Why that final estimate came in where it did, however, is a bit of a head-scratcher—especially because, in theory the results could have been even higher than the 240-mile projection.

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As to what caused the lower-than-expected outcome, the easy answer is, well, lower than expected efficiency. But where those efficiency losses occurred is an important question for Jaguar. According to researchers at Carnegie Mellon University’s Department of Mechanical Engineering, who dug into the available data over the last week, it doesn’t actually appear to be a problem with the most likely target—the 90-kWh battery pack. “What we’re seeing, even with the worst possible battery discharge efficiency, is that the numbers don’t check out,” said engineer Shashank Sripad, who conducted an initial investigation with colleague Venkat Viswanathan and others. “There is a chance that the motors are not efficient at all, or the way they have been incorporated into the powertrain might be causing the low efficiency.” The CMU engineers frequently analyze new electric vehicles: comparing them against models they’ve developed detailed knowledge of, while factoring in drag coefficients, frontal area, mass, the rolling resistance of the tires, the battery discharge efficiency, and the total powertrain efficiency. With that data, Viswanathan explains, they calculate the battery pack size that would be required to achieve the rated range published by the testing agency as a result of its drive cycle—that is, the speed and distance covered in the test. (In this case, the agency being the EPA.) “So if the battery pack we estimate matches the actual battery pack size, then the model [we created] checks out, and can be used to predict for another vehicle,” he says.

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