Automotive Design and Production

JUN 2013

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is positioned in the vehicle under the foorboard. Electrode material arrives in the Smyrna plant from Japan. It is in roll form. The roll is then cut into smaller rolls. The material is processed under humidityand temperature-controlled conditions. The air is fltered and workers handling the rolls wear clean-room suits (a.k.a., "bunny suits") to minimize the possibility of material contamination. Once the rolls of materials are dried, they are cut into individual sheets that are about the size and thickness of a piece of 8.5 x 11-in. paper. There is a high-speed robot used to stack layers of electrode material with a polymer-based separator between the anode (+) and cathode (-). There are 68 layers in a cell. The ends of the material are ultrasonically welded, and then the stacked sheets are wrapped in an envelope-like aluminum foil container. An electrolyte—the liquid material that facilitates the passage of ions in the cells—is injected into the cell. Then the cells age for several weeks. The package is cut so that gases created by this chemical aging are released, then it is permanently sealed. The cells are tested, trimmed to fnal dimensions, charged, and then tested again. A cell has a capacity of 33 ampere hours (Ah). A stack of four cells form a module. A module is placed in a steel case. Then the modules—48 of them—are assembled to form a 24 kilowatt-hour (kWh) battery pack for installation in the LEAF. That battery pack is capable of powering the car for approximately 84 miles (the mileage varies predicated on factors including driving behavior, temperature, and age of the battery). t The 2013 LEAF has been modifed in various ways to help improve range as well as to address customer concerns. What's interesting to note is that whereas midcycle enhancements generally occur after four years, the LEAF has been available on the U.S. market since December 2010. While all models have regenerative braking (when lifting from the accelerator or applying the brake pedal, the electric motor acts as a generator, sending energy to the battery), the SV and SL models have a "B-mode" (there are also "normal" and "Eco" mode) that provides more aggressive regenerative braking, to increase the amount of power sent back to the battery. q One of the customer-requested changes to the LEAF was putting the battery percent of charge in the center meter display. While people who drive gasoline-powered vehicles may pay comparatively scant attention to their fuel gauge, drivers of EVs like knowing precisely how much charge they have. There are other modifcations that help increase the range of the '13 by as much as 15% compared to the previous vehicle. There is a more effcient HVAC system. They've blocked off portions on either side of the grille to improve aero, according to Mike Higginbotham of the Nissan Product Planning Dept. The coeffcient of drag for the '13 is 0.28, compared to 0.29 for the '12. 39

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