Tesla: Five Minute Recharging On The Way, Without Battery Swap

By · July 16, 2013

Tesla SuperCharger

How fast, in theory, could a Model S driver fully charge and return to the highway? (Photo: Brad Berman)

California-based Tesla Motors is streets ahead of the competition when it comes to both the range of its electric cars and the speed at which they recharge. But Tesla isn’t content to simply maintain that lead: it wants to refill a battery pack in just five minutes, without battery swap technology.

Speaking with the MIT Technology Review, Tesla’s Chief Technical Officer JB Straubel said that in the future, Tesla cars will be able to refuel at its supercharger stations as quickly as five minutes. “It’s not going to happen in a year from now,” Straubel said in a recent interview. “It’s going to be hard. But I think we can get down to five to 10 minutes.”

Currently, the company's 120-kilowatt DC supercharger stations provide Model S owners—at no additional cost—up to 200 miles of range in about 30 minutes. Tesla also recently announced plans to offer battery swap capability at select Tesla superchargers for drivers who can’t—or don’t want to—wait for their car to recharge. The swaps, which would come with a fee, would provide a fully-charged pack in about 90 seconds (not including any time spent in queues).

Tesla isn’t the first company to explore the option of super-fast DC recharging. Last month, PluginCars.com reported on the Silex Hypercharger—a 1.5 megawatt ultra-fast recharging solution for the as-yet-to-be-built Silex Chreos. The grid-connected Hypercharger is hyperbole at this stage, but Tesla’s interest in super-fast charging provides more legitimacy to the concept. For example, to recharge an 85 kilowatt-hour Tesla Model S battery pack from empty to 80 percent full in five ten minutes would likely require a 720 kilowatt supercharger. That's half the power of the theoretical Silex Hypercharger.

Moreover, Tesla’s plans to introduce grid-tied energy storage (via stationary batteries) at its supercharger stations means it’s possible to provide high power to recharge an electric car quickly without dramatic impacts on local grids.  When not charging a car, these battery packs would be gradually replenished to prepare for the next customer, either through on-site solar panels or by a more modest flow of electricity from the grid.

Awareness of Hurdles

Summoning 720 kilowatts of power to supercharge a Tesla is theoretically possible, but there are significant technical hurdles, such as managing heat. The faster you charge a battery pack, the hotter it gets. While the Model S features an active liquid-coolant thermal management system capable of maintaining optimum temperature in the pack, the amount of heat generated by charging at 720 kilowatts is much higher.

Straubel is aware of the challenges. “To do that kind of charging, everything has to be designed and working in perfect synchrony,” Straubel explained.

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