Buying An Electric Car: What You Need to Know

By Larry Williamson

Larry Williamson

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6,772 views Apr 26, 2010

2011 Nissan Leaf

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2011 Nissan Leaf

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2011 Nissan Leaf

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2011 Nissan Leaf

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2011 Nissan Leaf

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2011 Nissan Leaf

Enlarge Photo

2011 Nissan Leaf

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Everyone pretty much knows what to look for when buying a gasoline vehicle. But what about an all-electric vehicle, of the sort that will go on sale at the end of the year?

Here's some background information on the technologies used, and the few differences in the instrument panel you'll see.

First, there are two motor types used in electric vehicles: alternating current (AC) or direct current (DC).  Electric cars from major automakers like Nissan, Chevrolet, and Toyota are exclusively AC, while the DC motors remain with the hobbyist.

AC motor systems are widely available, but they're more expensive due to the need for more electronics. The motors have higher speeds: 8,000rpm to 10,000rpm versus 6,000rpm to 7,000rpm with DC motors. And they require less maintenance because they lack mechanical brushes.

AC motors are also sized differently than DC ones; the larger the diameter of a DC motor, usually the more powerful it is.

Second, the motor controllers are one package all inclusive on the AC system, but a separate controller is required with the DC system.  The controllers are the brains of the system and the controller electronics have different voltages and amp ratings for the variety of AC motor available, while the DC motor selection is much less and voltage amp ratings become less of a requirement.

Lastly, the battery packs that power the motors have different voltages. Most DC systems run battery packs from 72 to 144 Volts, while AC packs can run at various DC voltages that are converted to the specific AC voltage chosen by the manufacturer for use in their specific vehicle.

Charging the battery packs has to be considered as well; each vehicle requires a charger from the manufacturer. While there is now a universal connector (known as the J-1772 standard) for the charging cable, there is no single universal charger.

Now that we have the basics of all electric vehicles, how does a driver determine what is happening with the vehicle?

The all-electric vehicle is not that different to a gasoline vehicle.  Gauges are mostly the same; EVs too need a speedometer, and warning lights for the 12-Volt electrical system, brake system, seat belts, and airbags. There may also be a motor-speed indicator (similar to a tachometer), and a volt meter for the auxiliary 12V battery.

But you're not likely to see a temperature gauge, oil pressure gauge, check-engine light, or warning lights for the oil system, cooling systems, or emissions control system.

The real difference is with the battery pack and its monitoring.  A state-of-charge (SOC) meter indicates the battery pack's capacity in amp-hours. In many electric cars, about 80 percent of the useable charge on the battery pack is consumed in normal operation, with 20 percent kept in reserve to protect the pack against damage from total discharge.

The number of amp-hours consumed determines the vehicle range.  The faster you use energy, the less range there is. It's just the same as in a gasoline car, where the higher your speed, the lower your gas mielage.  Just like in a gasoline car the faster you drive the less mpg.

A State of Charge gauge indicates how fully the car is charged compared to its to capacity; some may be calibrated in miles of range rather than SoC percentage.

Driving an all-electric vehicle is comparable to driving a gasoline vehicle, but without noise or emissions, along with much lower maintenance costs. And drivers will have just a few new gauges to become familiar with.

Keep these few things in mind when you buy your first all-electric vehicle, and it should be an enjoyable experience.

And what are those electric vehicles? By the end of this year, the 2011 Nissan Leaf and 2011 Coda Sedan will be the first all-electric vehicles offered for sale in the U.S. for almost a decade.