Leaf to be sold with battery pack at C-segment price

  • 11-Mar-2010 08:14 EST

Laminar cells show through a cutaway of battery containers mounted in a tray that bolts to underbody.

It won't be an only car for most people, but the forthcoming Nissan Leaf and its "over 100 miles" range is being made market-ready as a 4/5-passenger electric vehicle (EV) sedan that can handle 95% of the daily driving needs of Americans. It could be the first EV sedan to reach the U.S. market when it becomes available later this year. It will be both leased and sold to fleets and individuals.

Despite earlier reports hinting otherwise, the Leaf's lithium-ion battery pack will be part of the price (to be announced imminently). Nissan has said the price will be about that of a well-equipped C-segment model.

The automaker plans to produce 50,000 units at a Japanese plant for worldwide sale starting later this year, later adding capacity at its plant in Smyrna, TN. Capacity at the battery plant in Japan is 65,000 packs annually, with a plant in Smyrna, TN, to come on stream in late 2012 capable of producing up to 200,000 sets of batteries. Battery plants also will be built in the U.K. and Portugal.

The "over 100 mi" (160 km) claim is derived from the U.S. EPA's LA-4 urban driving cycle, operation at well below the 90 mph (150 kph) top speed of the Leaf. The figure apparently does not include operation in an "ECO" mode, which could extend range about 15-20%, AEI was told. Also, there is the "running out of juice" mode, in which the car will operate at reduced power and accessory load.

What happens if the battery pack is "empty" and there is no place to plug in? The driver will get plenty of warning as capacity wanes—more than something akin to the "low fuel" icon, AEI was told by Mark Perry, Nissan Americas Director of Product Planning. Further, he said, Nissan is working with road service providers such as AAA to carry special charging packs that can recharge sufficiently in minutes "to get the car home or to a charging station."

The vehicle's navigation system has a map showing nearby public charging stations. Nissan is targeting initial EV distribution for those geographic areas with public and private support for electric vehicle charging.

How long will the Li-ion batteries last? California law requires a 10-year, 150,000-mi warranty, so even though the federal warranty may be only 8 years, 80,000 mi, the system is designed for the California regulations. Perry said the first-generation battery pack is expected to retain 70-80% of its initial life after 10 years. The Leaf reportedly will maintain a 100-mi range for 10 years, even with the 20-30% battery deterioration. That would indicate that the 100-mi range is a conservative specification.

The battery is high-density laminar-cell Li-ion type with manganese oxide in the cathode, characteristics of a design with low internal resistance, and as a result good thermal stability. The pack weighs 480 lb (218 kg) including the control module and is rated at 24 kW·h total capacity, with an energy density for the cells of 140 W·h/kg, indicating a weight for the cells alone of about 378 lb (171 kg). The front-drive motor is rated at 80 kW and 280 N·m (207 lb·ft).

Vehicle weight has not been disclosed. The weight of battery pack and tray, and the control system, is partly offset by the absence of an engine, exhaust system, and fuel tank. The transaxle, which has an electric motor, is simpler but perhaps no lighter. The vehicle itself sits on a 106.3-in (2700-mm) wheelbase and has a 175-in (4445-mm) overall length.

Nissan and battery partner NEC are in a joint venture called AESC (Automotive Energy Supply Corp.). AESC has had considerable developmental and testing experience with the battery design and is confident both in the durability and opportunities for cost reduction. So, Nissan will price the Leaf based on an optimistic view of battery useful life expectancy, Perry said.

There are two charge connectors, one for high-voltage household current (minimum 200 V), a second for a special quick-charger. Charging time is 6-8 h on high-voltage household current, 30 min for an 80% charge with the special unit, rated at 50 kW ac. It can be installed in a home as well as used for a public station.

The pack, as with the designs of other EVs, rests on a tray that bolts up to the vehicle underbody, creating a sandwich with the interior floorpan, so replacement is straightforward.

While the Leaf is plugged in, its onboard IT system can be programmed by cell phone to precondition the passenger compartment, activating either the positive-temperature-coefficient heaters and/or the air-conditioning system. In addition to the benefit of a comfortable interior for the driver upon entry, the climate-control system does not have to run at peak power draw once the vehicle is under way.

Like hybrids, the Leaf is designed for minimum road load power requirements, including low-rolling-resistance tires. At 0.29 Cd, the Leaf's air resistance is not as good as the Prius's 0.25 Cd, but packaging for interior comfort was a priority, Perry explained.

Nissan's next EV steps are in development. A light-commercial van will follow, based on one that has been on auto show display, and then a high-performance Infiniti four-passenger car. The van is slightly larger than the Ford Transit Connect, also going EV, so Nissan surely will watch the new Ford entry for a marketing clue.

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