Design
The Leaf's frontal style is characterized by a sharp V-shape design with large, up slanting light-emitting diode (LED) headlights that create a distinctive blue internal reflective design. The headlights also split and redirect airflow away from the door mirrors, which reduces wind noise and drag. The headlights consume 50% less electricity than halogen lamps.[33] Nissan sought to make the Leaf appealing to mainstream drivers by giving it a familiar sedan- and hatchback-like design.[34] The bottom of the car has aerodynamic paneling to reduce drag and improve aerodynamics as much as possible.[35]
Leaf interior
Leaf electronic control unit
Leaf lithium-ion battery pack
[edit] Powertrain
Nissan says that the car has a top speed of over 150 km/h (93 mph). Its motor is rated at 80 kilowatts (110 hp) and 280 newton metres (210 lb·ft).[36] Unofficially, 0 to 60 mph (0 to 97 km/h) performance has been tested at 9.9 seconds.[2]
The Leaf uses a front-mounted electric motor driving the wheels, powered by a 86 megajoules (24 kW·h) lithium ion battery pack rated to deliver up to 90 kilowatts (120 hp) power.[37] The pack contains air-cooled, stacked laminar battery cells with lithium manganate cathodes.[38][39] The battery and control module together weigh 300 kilograms (660 lb) and the specific energy of the cells is 140 W·h/kg.[36] Each battery pack costs Nissan an estimated US$18,000 (as of May 2010[update]).[40][41] Under its five-cycle testing, the United States Environmental Protection Agency found the Leaf's energy consumption to be 765 kJ/km (34 kWh/100 miles) and rated the Leaf combined fuel economy equivalent at 99 MPGe (2.4 L/100 km), with an equivalent 106 mpg-US (2.22 L/100 km; 127 mpg-imp) in city driving and 92 mpg-US (2.6 L/100 km; 110 mpg-imp) on highways.[7][8]
[edit] Battery
The 24 kWh battery pack consists of 48 modules and each module contains four cells, a total of 192 cells, and is assembled by Automotive Energy Supply Corporation (AESC) – a joint venture between Nissan, NEC and NEC Energy Devices, at Zama, Japan.[42][43][44] Since the battery is the heaviest part of any EV, Nissan housed the battery pack below the seats and rear foot space to keep the center of gravity as low as possible and also results in increased structural rigidity as compared to a conventional five-door hatchback.[2][44][45]
The battery pack is expected to retain 70% to 80% of its capacity after 10 years but its actual lifespan depends on how often fast charging (440-volt) is used and also on environmental factors.[39] Nissan stated the battery has a "lifespan of 5–10 years under normal use".[46] The Leaf's battery is guaranteed by Nissan for eight years or 100,000 miles (160,000 km)[47][48] (see Warranty sub-section below under United States for limitations).
In addition to the main battery, the Leaf also has an auxiliary 12-volt lead-acid battery that provides power to the car computer systems and accessories such as the audio system, supplemental restraint systems, headlights and windshield wipers.[49] The small solar panel on the Leaf rear spoiler (in the United States, only comes with SL trim[50]) helps to charge this accessory battery.[51]
Nissan recommends owners the following preventive actions to help maximize the lithium-ion battery’s useful life and its ability to hold a charge:[49]
* Avoid exposing a vehicle to ambient temperatures above 120 °F (49 °C) for over 24 hours.
* Avoid storing a vehicle in temperatures below −13 °F (−25 °C) for over 7 days.
* Avoid exceeding 70 to 80% state of charge when using frequent (more than once per week) fast or quick charging.
* Allow the battery charge to be below at least 80% before charging.
* Avoid leaving the vehicle for over 14 days where the Li-ion battery available charge gauge reaches a zero or near zero (state of charge).
Range
According to Nissan, the Leaf's expected all-electric range is 160 kilometres (100 mi) on the EPA city driving cycle and remains the same as the EV-11 prototype.[52] However, the United States Environmental Protection Agency official range is 117 kilometres (73 mi) based on the five-cycle tests using varying driving conditions and climate controls.[7][8] The Federal Trade Commission, which is supposed to label all alternative-fuel vehicles, disagrees with the EPA rating, and considers that the correct range is between 96 to 110 miles (154 to 180 km). Although the FTC does not conduct its own tests as EPA does, it relies on a standard set by SAE International and the results reported by automakers.[53] The Leaf has a range of 175 km (109 mi) on the New European Driving Cycle.[9]
Based on third-party test drives carried out in the US, reviewers have found that the range available from a single charge can vary up to 40% in real-world situations; reports vary from about 100 kilometres (62 mi) to almost 222 kilometres (138 mi) depending on driving style, load, traffic conditions, weather (i.e. wind, atmospheric density), and accessory use.[54][55] Nissan tested the Leaf under several scenarios to estimate real-world range figures, and obtained a worst case scenario of 76 kilometres (47 mi) and a best case scenario of 222 kilometres (138 mi). The following table summarizes the results under each scenario tested using EPA's L4 test cycle and presents EPA rating as a reference:[56][57]
Summary of the Nissan's results using EPA L4 test cycle
operating the Leaf under different real-world scenarios[56][57]
Consumer Reports tested a Leaf loaner under cold-weather driven as a daily commuter. The average range obtained was 105 kilometres (65 mi) per charge with temperatures varying from 20 to 30 °F (-7 to -1 °C). The magazine also reported one trip under a temperature of 10 °F (−12 °C) that began with the range panel indicator showing 32 kilometres (20 mi) remaining. After 13 kilometres (8 mi) the Leaf drastically lost power and dropped its speed and continued to run slower until the last stretch was completed almost at walking speed. Consumer Reports concluded that the Leaf works as designed under cold temperatures but a more accurate range indicator is desirable.[58]
In June 2011 Nissan reported, based on data collected through the Leaf's advanced telematics system, that most Leaf owners in Japan and the United States drive distances less than 60 miles (100 km) per day.[59] Nissan also found that on average owners charge their electric cars for two hours a night, and occasionally some owners drive two days on one charge.[60]
Recharging
The Leaf has two charging receptacles: a standard SAE J1772-2009 connector for level 1 and 2 charging (120/220 volts AC)[61] and a JARI high-voltage DC connector designed by TEPCO for DC fast charging (480 volts DC 125 amps)[62] using the CHAdeMO protocol.[63]
The Leaf's charging port with two inlets is located at the front of the car.
Using the on-board 3.3 kW charger[64] the Leaf can be fully recharged from empty in 8 hours from a 220/240-volt 30 amp supply (5.2 kW allowable draw[65]) that can provide the on-board charger its full 3.3 kW of usable power.[66][67]
In North America and Japan using a standard household outlet (120-volt, 15 amp breaker, 12 amp maximum allowable draw,[65] 1.4 kW) and the 7.5-meter (25 ft)[68] cable included by Nissan, the Leaf will regain approximately 5 miles of range per hour. This type of charging is intended for convenience use when making stops or for emergency charging if you are within a short range of the charging destination.[66]
United States electrical regulations require a 240-volt charging station to be permanently wired to an AC outlet unless proper interlock mechanisms are available to ensure the charging current can be safely turned on and off.[65] Nissan selected AeroVironment to supply its charging dock and installation services in North America[69] (see the United States section below for more details).
Using DC fast charging, the battery pack can be charged to 80% capacity in about 30 minutes.[70] Nissan developed its own 500-volt DC fast charger that went on sale in Japan for ¥1,470,000 (around US$16,800) in May 2010 and plans to install 200 at dealers in Japan.[71][72] Nissan warns that if fast charging is the primary way of recharging, then the normal and gradual battery capacity loss is about 10% more than regular 220-volt charging over a 10-year period.[39] Other companies make compatible charging stations, and companies and local government have various initiatives to create networks of public charging stations[66][73] (see electric vehicle network).
Nissan plans to double the power of the on-board charger to 6.6 kW by sometime in 2012 (2012 or 2013 model year). They are also studying the possibility of offering upgrades for the 2011 year model.[74][75]
[edit] Technology
Nissan Leaf SL spoiler-mounted solar panel
The Nissan Leaf employs an advanced telematics system called "Carwings" which originally was only available in Japan.[76][77] The system sends and receives data via a built-in GPRS radio similar to the connectivity of mobile phones. Carwings is connected any time the car is in range of a cell tower and it makes possible several user functionalities, such as position and possible range on a map and which charging stations are available within range. The system also tracks and compiles statistics about distance traveled and energy consumption and produces daily, monthly and annual reports of these and several other operational parameters. All information is available in the Leaf's digital screens.[76][78] Users' mobile phones can be used to turn on the air-conditioner and heater, and reset charging functions even when the vehicle is powered down. This remote functionality can be used to pre-heat or pre-cool the car prior to use while it is still charging so that less energy from the battery is used for climate control. An on-board remote-controlled timer can also be pre-programmed to recharge batteries at a set time such as during off-peak rates.[79] The Leaf's SL trim has a small solar panel at the rear of the roof/spoiler that can trickle charge the auxiliary battery.[80]
Leaf's dashboard panel showing driving range (on right) and other performance parameters
Due to significant noise reduction typical of electric vehicles that travel at low speeds, the Leaf includes digital warning sounds, one for forward motion and another for reverse, to alert pedestrians, the blind, and others of its presence.[81][82] For this purpose Nissan created the Vehicle Sound for Pedestrians (VSP) system, which also will be used in the upcoming Nissan Fuga hybrid, due in 2011. The system developed makes a noise easy to hear for those outside in order to be aware of the vehicle approaching, but the warning sounds do not distract the car occupants inside. Nissan explained that during the development of the sound, they studied behavioral research of the visually impaired and worked with cognitive and acoustic psychologists.[82][83][84] The sine-wave sound system sweeps from 2.5 kHz at the high end to a low of 600 Hz, an easily audible range across age groups. Depending on the speed and if the Leaf is accelerating or decelerating, the sound system makes sweeping, high-low sounds. The sound system ceases operation when the Nissan Leaf reaches 30 kilometres per hour (19 mph) and engages again as car slows to under 25 kilometres per hour (16 mph). The driver can turn off sounds temporarily through a switch inside the vehicle, but the system automatically resets to "On" at the next ignition cycle. The system is controlled through a computer and synthesizer in the dash panel, and the sound is delivered through a speaker in the front driver’s side wheel well.[82][83][85] After the new sounds were publicized, the US National Federation of the Blind commented that "while it was pleased that the alert existed, it was unhappy that the driver was able to turn it off."[82]
Safety
The Nissan Leaf qualified as winner of "Top Safety Pick" by the Insurance Institute for Highway Safety. The Leaf received the top ratings of "Good" for front, side, and rear impact crash tests, and also on rollover protection. All injury measurements except one were rated good, indicating a low risk of significant injuries in crashes according to the scale of severity employed in the IIHS’s testing.[86][87] The European New Car Assessment Programme (Euro NCAP) awarded the Leaf the highest five star car safety rating. The Leaf earned an 89% rating for adult safety, an 83% rating for child protection and an 84% rating for its on-board safety assist systems. It also earned a higher-than-average 65% score for pedestrian safety.[88]
