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Range anxiety, or slow chargers? Faster electric car chargers are on the way

Consumer Reports News: December 07, 2011 03:23 PM

Clearly, the main problem with electric cars is “range anxiety”--drivers’ fear of running out of electricity before they reach their destination and ending up stranded by the side of the road. (Read: “Nissan Leaf: Commuting and justified range anxiety.”) But the problem may not stem from the limited range alone.

After all, ordinary cars can run out of gas too, just after a lot more miles. Compounding the range anxiety is the time it takes to “refill” electric cars. It takes hours to recharge electric cars and faster charging locations are scarce, making EV operation quite different than living with a gasoline-fueled car that can be refilled in 5 minutes from a gas station at near any street corner.

Surveys reveal that even the short 35-mile electric range of the Chevrolet Volt will suffice for most Americans’ daily trips. The Nissan Leaf, which can go 75 miles on a full charge, should cover the regular commuting needs of more than 90 percent of the driving population. (Read: “Survey: Car owners want better fuel-economy, support increased standards.”)

The added cause for anxiety, then, is the need for a prolonged recharging process on those occasions when an electric car can’t meet your needs. Even if you find a place to charge, say at the shopping mall, the gain is hardly worth it. You might get a few more miles in 45 minutes of charging, but that is likely not enough to get home or continue running errands.

Research shows that range anxiety causes EV drivers to charge at every opportunity, even if their cars actually can get them where they’re going without the extra juice. To address this concern, the next wave of electric cars will have faster on-board chargers that can get more out of a few minutes charging than today’s models. Every EV has an on-board charger that funnels the electricity that comes out of the grid into the car battery. The larger the funnel, the faster the charging.

The new electric cars on the way, including the Ford Focus EV and the 2013 Nissan Leaf, will include 6.6-kW on-board chargers, rather than the 3.3-kW chargers in today’s Nissan Leaf and Chevrolet Volt. (For the record, Mark Perry, Nissan’s director of product planning in North America, says no faster charger was commercially available for automotive-grade mass production in time for earlier Leafs.) As a point of reference, figure the current 3.3-kW charger draws a little more current than two large hair dryers; a 6.6-kW charger pulls twice that.

In practical terms, this will cut the charging times for these new electric cars in half, from six hours on a 240-volt, Level 2 charger for the Leaf to just three hours. (If the Chevy Volt had a 6.6-kW charger, it could recharge fully on 240 volts in less than two hours.) This advance can cut the time it takes to charge the Leaf fully on a standard 120-volt outlet to just overnight, reducing the need for a special 240V wall-mounted unit for some people. Now it takes 16 hours or more.

A useful way to look at the improvements in charge time is to consider the number of miles you could gain in an hour of charging. Such a calculation represents the errand-running situation when you may discover you’re running low on juice. For now, the best outlet you’re likely to find on the run will be 120 volts. In an hour, on their 3.3-kW chargers, the Leaf or the Volt can regain about six miles. A car with a 6.6-kW charger could gain about 12-1/2 miles, perhaps enough to ease any range anxiety and expand your radius for errands.

If you live in an area with a public network of Level 2 (240 volt) chargers, you could get 24 miles in an hour of charging, or perhaps more relevantly, you could regain those 12-plus miles in just a half hour. (Widespread installations of so-called “DC fast chargers” that can recharge the batteries to 80 percent capacity in a half hour are still several years away.)

For reference, here’s a chart of how many minutes it takes on a charger miles of range gained for today’s electric cars and estimates for those on the way:

EV charge time/mile Onboard charger Tested/
120 volts (Level 1) 240 volts (Level 2)
Min. charging / mile range Miles per 30 min. charge Full
Min. charging / mile range Miles per 30 min. charge
2012 Ford Focus EV* 6.6 kW 75 7.5 6.0 5.0 3 2.4 12.5
2013 Nissan Leaf* 6.6 kW 75 7.5 6.0 5.0 3 2.4 12.5
2011 Nissan Leaf 3.3 kW 75 16 12.8 2.3 6 4.8 6.3
2011 Chevrolet Volt 3.3 kW 35 10 17.1 1.8 4 6.9 4.4
2012 Mitsubishi I* 3.3 kW 64 12.5 11.7 2.6 5 4.7 6.4
2011 Ford TransitConnect EV* 3.3 kW 64 12.5 11.7 2.6 5 4.7 6.4
* based on estimated range and charge times

Ultimately, 6.6 kW chargers may not be enough, even at Level 2, to facilitate a mass transition to EVs. But these faster chargers point to progress and might help some potential EV intenders to get over the hurdle to driving electric cars.

For more on alternative fuels, see our special section.

Eric Evarts

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