Rapid Charging Electric Cars: How Fast, How Soon?

Before unveiling the concept version of its Model S sedan, an $57,400 electric car that Tesla Motors wants to build using loans from the Department of Energy, the startup said the Model S battery would be designed to handle rapid charging. Last week, at the Model S unveiling in Los Angeles, Tesla revealed that an optional “QuickCharge” battery would get a full charge in 45 minutes from a 480V outlet. For the standard version, Tesla plans to use a battery that can recharge at a typical 220V outlet in about four hours.

While the Model S is in the concept phase of development, rapid charging represents a very real focus for battery developers and electric car makers. Nissan is working on an electric car that it says is on track to have a 100-mile range and 26-minute charge time. Earlier this month, researchers from MIT said they had developed a process that within three years could lead to electric car batteries able to recharge in as little as five minutes. How quickly can we really expect the early generations of electric vehicles to recharge — and what does it mean for the practicality of EVs?

I asked Mike Omotoso, J.D. Power & Associates’ alternative powertrain specialist for North America, how realistic it would be for a driver to charge up at a 480V outlet during a long road trip. “A 480V outlet is a little unusual,” used mostly for higher-power industrial applications, Omotoso said. While some airports have 440V fast-charging stations, he said, a typical U.S outlet is 120V. We use 220-240V outlets for large home appliances like ovens, furnaces and clothes dryers.

The higher the voltage, the shorter the charging time — but not without a tradeoff. “It is also more dangerous to have higher voltage,” Omotoso explained. “Buyers of the Model S can play it safe (and have more flexibility in terms of where they can charge the car) by using the standard 120V outlet, but the charging will take longer.”

Since rapid charge times come on the condition of available outlets, higher-voltage charging infrastructure would need to be put in place — built over the course of years — to facilitate the charge times some automakers are shooting for. The Renault-Nissan Alliance launched a pilot project in Arizona earlier this month to test out a charging network ahead of the planned 2010 launch of its electric vehicle.

EV infrastructure startup Better Place, on the other hand, which has several countries on board with its plan to build large-scale networks of battery swap stations and charge points, has a different plan. The company says its charge spots would have voltage on par with standard household outlets. For on-the-go juice ups, the idea is to exchange your dead battery for a fresh one owned by Better Place.

Extended-range electric vehicles — such as the Chevy Volt, which GM says will recharge in three hours — offer another route, adding a small gas engine to keep drivers from feeling stranded without access to fuel. Which scheme wins may depend (in addition to financing hurdles) as much on our driving habits and patience as on advances in technology. How long would you be willing to wait for an electric car to recharge, and how much range would you need to have to feel secure hitting the road in an all-electric car?

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