Leaf incorporates features to prevent range anxiety

  • 10-Feb-2011 09:33 EST
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Charging stations are being installed in parking lots.

Range anxiety has been cited as a major concern among potential buyers of the new Nissan Leaf and forthcoming all-electric vehicles (EVs) from other makers. However, as the pioneer, Nissan has taken many steps to ensure the term is more one of early conjecture than a real-world issue.

Leaf has several “range awareness” features in its display panels, including a sophisticated version of the “low fuel” warnings on gasoline engine cars. Further, there are indicated ways—including an “ECO” mode, to extend range, equivalent to what the driver of a gasoline engine car might do if the low-fuel light goes on and he or she is nowhere near a filling station.

The U.S. Department of Energy, state and local governments, and private investors expect to have a reasonable charging infrastructure in place this year. Nissan anticipates a network of 13,000 charging stations by 2012, primarily in areas where the EVs will be sold (about 10% of the number of gasoline filling stations for the entire country). At first, many will be free. But as the EV population builds and more stations are built with little or no governmental assistance, the driver will have to swipe a credit card or pay a premium in a parking facility.

Early EV buyers will have read all the data and will make the purchase work. They are unlikely to run out of “juice” and have to be flat-bedded to a charging station. Nissan says at least 75% of the early adopters will have a garage and install a 240-V charger, which permits recharging in 6 to 8 h, as the cost will be covered by federal and other rebates (120-V recharging takes as long as 20 h). The 120- and 240-V charging uses a charge-cord-to-receptacle that meets SAE J1772.

Further, many “green” companies have announced they will provide on-site charging at their facilities. Additionally, even many apartment dwellers may see charging stations in their building parking facilities.

Nissan believes Leaf’s range should satisfy an overwhelming majority year-round. Although the U.S. EPA’s window sticker number is 73 mi, range is likely to be measurably higher in spring and fall, lower in winter and in peak temperature periods of summer. Nissan has been rating the Leaf for about 100 mi (160 km), with a drop-off to perhaps 60 mi (96 km) in winter cold when the resistance heaters are on, and low ambient temperatures also reduce battery output. However, these numbers do not factor in range-extending features.

Mark Perry of Nissan product planning, has noted more than 72% of motorists drive fewer than 50 mi (80 km) on weekdays (this distance also applies to over 66% on weekends). Further, buyers likely are families who have a second car for longer trips. Ford and Mitsubishi, two other manufacturers who will be introducing all-electric cars this year, have looked at the same numbers, as they will have similar EV range.

Range awareness, extenders displayed

Nissan’s range awareness features include:

• Continuous update of range, in miles.

• Climate control off algorithm. An algorithm calculates the increase in range if A/C or heat is turned off and displays that. Motorists often turn off A/C with gasoline engine cars to improve fuel economy, so they should accept this step.

• Reachable area shown on navi map. There is a white circle for an area easily reached, a gray circle for a larger area, but still well within the vehicle’s capability. These circles also can be expected to be well within the driver’s daily mileage pattern, so should be confidence builders.

• A “how am I driving” display. If the vehicle is being driven conservatively, digital “trees” will “grow” (up to three), and the numeric display will show greater range.

The Leaf has range extenders:

• “ECO” mode. “Pushback” from the accelerator encourages light-footed driving, and regenerative braking becomes more aggressive (the car slows more dramatically when the driver takes his foot off the accelerator). Other EV manufacturers will have similar systems.

•“Preconditioning.” The cabin can be made warm in winter or cool in summer while plugged in. So when the motorist unplugs and drives off, initially he or she does not have to use much A/C or heat. Preconditioning can be preset or even enabled remotely with a smartphone app.

• Cold-weather package, available later this model year. Heated seats and steering wheel reduce need for cabin heat. A battery “blanket” keeps the battery pack warmer, so it can deliver more of its charge. This concept is similar to the insulating blankets many people install on the 12-V battery in their gasoline engine cars to ease cold starting.

• Low-battery warning. With approximately 12 to 13 mi (19 to 20 km) of range remaining, a low-battery warning will come on, (top speed will have been reduced by a complex algorithm to about 55 mph (88 kph) and continue to drop as the vehicle is driven. The driver presses a navi system button and a list of the nearest charging stations is displayed. Initially, of course, there is no guarantee the motorist is within range of a charging station, but as the charging infrastructure builds, the navi software could tie an alert to the distance to a station vs. a programmed destination, if the trip is beyond the EV range. Even when the battery is too depleted for normal operation, the EV will retain the ability to slowly pull safely off the road vs. a gasoline engine car just rolling to a stop.

The Leaf also has “security blanket” features:

• Continuous updating of charging system locations and driving directions to the chosen one. As the navi screen fills with more and more symbols indicating locations of charging stations, driver confidence will rise. With many charging stations located in parking lots, the EV commuter will be assured he can add more side trips to his normal daily routine.

• Free roadside assistance for two years, so the driver is never stranded. Cross Country Automotive Services, Nissan’s service provider, initially will flatbed the Leaf but, as volume increases, may add roadside charging.

• Smartphone app reports state-of-charge if Leaf is plugged in while the driver is at work or shopping. If the charge cord becomes unplugged, the phone displays a notice.

• Optional capability for dc fast charging, which can bring the battery pack from under 20% up to 80% in less than 30 min. One DOE-sponsorship, the EV Project, is paying the $700 option price for buyers who participate in its data-mining work. There are two approaches to fast charging, both are from a 480-V, three-phase A/C source. One standard already developed, “CHAdeMO” from Japan, requires a specific receptacle (the “TEPCO-JARI”), which will be used on the Leaf and Mitsubishi I-MIEV, and therefore is likely the choice for the stations initially deployed. A proposal to modify SAE J1772 to incorporate dc fast charging still is in development. Its appeal: a single receptacle for all three voltages.

The charging infrastructure is what will inspire the greatest confidence for those who are not early adopters. They will learn from reading articles, seeing TV reports, and actually seeing charging stations in areas in which they now drive their gasoline engine cars.

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