Ingenieur Vol. 74 Ingenieur Vol 72, April-June 2018 - Page 27

Tesla car battery Powerful Battery Cells Inside a Tesla Model S battery pack (Source: Electrek) cells, but thousands of small, cylindrical, lithium- ion commodity cells like those used in consumer electronics. It uses a version of these cells that is designed to be cheaper to manufacture and lighter than standard cells because of the advanced thermal management system and an intumescent chemical in the battery to prevent fires. Panasonic is the sole supplier of the cells for Model S, Model X, and Model 3 and co-operates with Tesla in its huge battery factory called Gigafactory in Nevada, USA. Battery cells are simple devices consisting of three basic components: two electrodes, the negative anode and the positive cathode separated by a chemical “soup”, called the electrolyte. When Lithium ion batteries are charged, Lithium ions are forced to migrate to the negative electrode where they are deposited. During discharge the Lithium ions reverse direction for the Cathode. Tesla has managed to pack more and more battery cells to power its cars. The first generation 18650 form battery cells, used by the company in Tesla’s first-generation Roadster, are still used in the Model S and Model X. The latest 21700 cells are used exclusively in the Tesla Model 3 and in energy storage products. They are a huge improvement over the 18650 battery cells with regard to energy density (by as much as 30%) and packaging possibilities. The 21700 cells have a diameter of 2 1mm, length of 70mm and volume of 24.245mm³. This is 46% more than the 18650 cells. “They are also about 15% more energy efficient,” according to a statement by J. B. Straubel, Tesla’s chief technology officer. Energy density is said to be 877.5Wh/L and cell capacity is 21.275Wh. 25