Nissan has launched production in its new battery plant in Smyrna, Tenn. The plant, which is making battery components for the ramp-up of production of the 2013 Nissan LEAF early next year, is located adjacent to Nissan’s existing vehicle assembly plant in Tennessee, which itself has been retooled to accommodate production of the Nissan LEAF.
Combined, the construction of the battery plant and modification of the Smyrna manufacturing facility represent an investment of up to $1.7 billion when built to full capacity. The project is supported by a US Department of Energy (DOE) loan for up to $1.4 billion, issued as part of the Advanced Technology Vehicles Manufacturing Loan Program, program authorized by Congress as part of the Energy Independence and Security Act of 2007. (Earlier post.)
The facility is capable of expanding to produce modules for up to 200,000 battery packs annually depending on market demand. Those batteries can serve as the power source for the Nissan LEAF and for future vehicles that could be added to the portfolio, Nissan said.
Since December 2010, Nissan has delivered more than 18,000 LEAFs to US customers and more than 46,000 worldwide.
|Technicians at Smyrna prepare equipment to unload an electrode mother roll in the unpacking room. Click to enlarge.
Each battery pack consists of 192 cells contained in 48 separate modules. One module contains four 33 Ah cells; the battery pack has total capacity of 24 kWh.
Each cell is a laminated structure. The electrodes arrive as a “mother roll” that is cut into smaller rolls to be dried thoroughly, cut to to correct size, and stacked as layers of anode-separator-cathode. The layers are connected by tabs that are welded, and then the stacked sheets are sealed in an aluminum foil material, thus creating the cell.
|Cells travel down a conveyor following completion of the aging process. Click to enlarge.
After lamination, the cells are injected with electrolyte, then aged to allow the cell chemistry to form properly. After final testing, they are trimmed to final size, and charged and tested.
The cells are then mounted in the module which is rigidly secured into the pack. It is then encased in a steel structure that is sealed to protect the components from hazards such as water, fire and impact from a collision.
The battery pack is located under the floorboards, which allows for more cabin space and lowers the LEAF’s center of gravity. This design results in better handling of the vehicle, and it adds another layer of protection to the battery pack.
|Assembling a battery pack at Smyrna. Click to enlarge.
Because of the compact cell design and layout structure, the battery pack also produces less heat overall, Nissan says. Rather than a liquid-based cooling system, the LEAF battery uses a convection-style cooling system where heat is transferred first from the cells to the modules and then to the mounting structure. Next it moves to the battery pack case and dissipates into ambient air. By not having a liquid-based cooling system, the vehicle weighs less, and the battery system is less complex.
The LEAF battery management system continuously monitors conditions, and the battery controller calculates the maximum output and remaining capacity based on battery pack voltage and current, individual module temperatures, cell voltage and bypass current.
The battery management system is able to optimize conditions to provide power on demand, and if necessary, it will respond to unexpected and extreme conditions by going to failsafe mode or in extreme cases, by completely shutting down. Once battery data comes through the battery controller, it is then transmitted to the vehicle controller, which directs the Nissan LEAF’s motor power.
The first batteries produced at the plant have completed the required aging process and are now ready to receive their first charge.
|Click to enlarge.
The Nissan LEAF is manufactured on the same line as Altima and Maxima so volume can readily be adjusted among the vehicles to meet demand. The 2013 model-year Nissan LEAF will receive a number of technological advancements and feature changes, which will be announced closer to the vehicle’s on-sale date in early 2013, Nissan said.
The recent growth of Nissan’s US manufacturing plants is part of a strategy to localize core-model production. By 2015, Nissan aims to have 85% of all Nissan and Infiniti products that are sold in the United States produced in North America. Nissan, which is in the middle of a product blitz launching five key models in 15 months, will report record sales for 2013 following a year of significant new vehicle introductions, such as the all-new 2013 Altima, Sentra and Pathfinder.