WITH electric cars and plug-in hybrids at last trickling into the showrooms of mainstream automakers, the dream of going gasoline-free is becoming a reality for many drivers. Cars like the Nissan Leaf and the Chevrolet Volt can cover considerable distances under electric power alone — certainly enough for local errands and even most daily commutes — while enabling their owners to shun gas stations.
Indeed, charging the car’s battery pack at home, or topping up at the office or shopping mall, will work fine for most drivers. But what about trips that are beyond the range of a single battery charge? Couldn’t a driver in need simply pull up to a charging kiosk and plug in for a rapid refill?
It’s not that simple.
Sure, there are already public charging stations in service, and new ones are coming online daily. But those typically take several hours to fully replenish a battery.
As a result, the ability for quick battery boosts — using a compatible direct current fast charger, the Leaf can refill to 80 percent capacity in 30 minutes — could potentially become an important point of differentiation among electric models.
But the availability of fast charging points has in part been held up by the lack of an agreement among automakers on a universal method for fast charging — or even on a single electrical connector. Today’s prevalent D.C. fast-charge systems are built to a standard developed in Japan by Nissan, Mitsubishi and Subaru in conjunction with Tokyo Electric Power.
Called Chademo, which translates roughly to “charge and move,” it uses a connector that is different from the plugs in most electric cars. As a result, a Chademo-compatible car like the Nissan Leaf requires two separate sockets.
Overcoming the limitation of a short driving range is vital to achieving acceptance by consumers who want uncompromised, do-everything vehicles. The potential solutions all have drawbacks. Larger batteries are expensive and saddle the car with added weight. An onboard generator turned by a gasoline engine, as used in the Volt plug-in hybrid and similar future models, are another possible solution, but such systems add cost and pounds — and compromise the emissions-free image that attracts consumers to electric cars in the first place.
Leisurely overnight recharging is no problem. All electric cars come with a standard charging cable that can plug into a common 120-volt household electrical outlet. More than just an extension cord, this cable incorporates various safety features.
“There is no energy flowing through the cord until the car talks to the box,” said Gary Kissel, an engineering specialist for General Motors, referring to the charging cord’s electronics. “It also has a G.F.C.I. and signals the car that the cable is connected, making it impossible for you to drive off if you forget that you’re plugged in,” he said, using the abbreviation for the safety provision known as a ground fault circuit interrupter.
The Leaf and the Volt, as well as future electric cars coming to the American market, can use these 120-volt cords interchangeably because they are all designed to the SAE J1772 standard. A task force assembled by SAE International, an organization of scientists and vehicle engineers, developed the design specifications for the J1772 standard through a committee of 150 carmakers, electrical equipment makers and utilities.
Other groups, including the American National Standards Institute, are also working on standards and codes for electric cars.
Charging an electric car on a 120-volt circuit, called Level 1 charging, is undeniably slow. The Volt requires about 10 hours to fully charge on 120 volts and the Leaf, with its larger battery, needs closer to 20 hours. For plug-in hybrids, which generally have smaller batteries, Level 1 charging works for overnight and at-work refills, but pure electrics need something stronger.
That next step, called Level 2 charging, uses a 240-volt circuit. Typically, this charging cable is not portable; instead, it’s hard-wired to a garage or charging station, though the actual charger is built into the car. These higher-voltage cables also cost extra — about $2,000, the majority of which goes to the installation.
“This is the type of charger we’ll be seeing in parking lots,” said Nancy Gioia, director for global electrification at Ford Motor. “The hardware on 120 volts won’t provide enough incremental range to satisfy customers.”
With a 240-volt unit, the Leaf can recharge a depleted battery in less than eight hours and the Volt can do it in about four. These chargers use the same SAE J1772 connection
As you might expect, with electric cars just starting to reach volume production these chargers are not yet common. Level 2 charging stations are planned for each of Nissan’s 1,100 dealers, but the Web site
lists on
ly about 1,350 charging stations of all types scattered across the 50 states, mostly in California and the Northeast. The Leaf’s navigation system can display nearby charging locations.
In the long term, however, commercial chargers will proliferate, especially as private companies get into the business. Among these is NRG, a power utility, which announced in April that it would install 120 Level 2 charging stations in Houston and Dallas-Fort Worth by the end of 2012. NRG will charge fixed monthly fees to use the stations, with a three-year contract. For unlimited usage the rate is $89 a month, or $1,068 a year — the equivalent of 7,000 miles in a car that gets 25 m.p.g. with gas costing $4 a gallon.
The NRG charging stations will incorporate not only Level 2 chargers, but also D.C. fast chargers. Fast chargers have complex hardware — a permanent installation, not an onboard system — that requires a connection to 480-volt three-phase alternating current. Sensitive circuitry is needed to convert this high-voltage A.C. power into direct current without frying the car’s battery. As you might expect, such chargers are expensive — at least $20,000 for the charger and another $20,000 for the installation.
The payoff is the ability to charge a Leaf’s battery to 80 percent capacity in half an hour, compared with six hours on a Level 2 charger or roughly 15 on a Level 1. Or put another way, 10 minutes on a D.C. fast charger can add about 30 miles of range.
The SAE committee is working on a modification of the J1772 connector to incorporate this high-powered D.C. charging as well as the existing Level 1 and 2 charging in a single connector.
“BMW prefers the SAE 1772 approach to having a single connector,” said Rich Steinberg, manager for electric vehicle operations and strategy at BMW North America, echoing the view of many carmakers.
The revised J1772 prototype will not be ready until this fall, according to the Peter Byk of SAE, and the final version is unlikely to be ready until late 2012.
At least in the view of the Leaf’s maker, there is no disaster in the offing.
“A Chademo charger could conceivably be reconfigured as an SAE charger,” said Mark Perry, product planning director at Nissan North America. “It could even have both plugs to accommodate all electric vehicles.”
As the only fast-charging game in town for now, 17 Chademo-type fast chargers, manufactured by AeroVironment of California, will be installed on Interstate 5 from the southern border of Oregon to the northern border of Washington this year. The plan is to eventually extend them all the way to the southern border of California.
Still, the experience will have its shortcomings. Consider a Nissan Leaf that can go about 70 miles at highway speeds on a full charge. At the 80 percent charge delivered by a fast chargers, that drops to 56 miles, which you’d cover in 48 minutes at 70 m.p.h. That means travelers would spend as much time charging as they would driving.
To match the convenience of a conventional car on the highway will require a combination of much greater electrical range with an even faster charging time, neither of which is around the corner. But for urban use, each new charger installation will improve the utility of all electric cars.
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