|The battery which Continental has developed for the Mercedes-Benz hybrid weighs around 25 kilograms and requires an installation volume of some 13 liters. Click to enlarge.|
Continental has begun series production of lithium-ion battery packs to be used in hybrid-electric cars. The initial packs produced at Continental’s plant in Nuremberg, Germany, will be installed as standard in the new Mercedes S400 BlueHYBRID, available from the middle of 2009. (Earlier post.) The 120V battery-powered electric motor in the Mercedes hybrid can boost the combustion engine by up to 19 kW.
The Continental battery pack, with cells from Johnson Controls-Saft (earlier post), weighs around 25 kg (55 lbs) and requires an installation volume of some 13 liters (0.46 cubic foot).
Continental’s Powertrain Division invested more than €3 million (US$4.4 million) in building up manufacturing capacity at the Nuremberg site. The company held a joint celebration this Wednesday in Nuremberg together with customers, suppliers and political and media representatives to mark the start of series production.
Continental’s battery management system (BMS) monitors the battery so that it is always within the optimum working range. The electronics compare the battery’s overall condition, temperature and energy reserves against its age; safety circuits prevent the energy storage unit from becoming too hot. A Cell Supervision Circuit (CSC) monitors the individual cells and ensures their optimum interaction.
The CSC balances the charge levels of all the cells in the battery to prevent cells from being permanently subjected to uneven loads. This helps to ensure that the lithium-ion batteries will really last—with unimpaired functionality, power and safety—for the required ten years or 160,000 to 240,000 kilometers. Batteries produced since last year as part of the pre-production series have been artificially aged in testing to simulate their use in vehicles over time.
|A resistance welding process joins the copper bus bars. Click to enlarge.|
Since the current inside the battery is not conducted via cables but along copper bus bars, a special welding resistance welding process (using 16,000 amps) is used to join the bus bars so that the current can then flow unimpeded past the welding seams and avoid power losses. The lithium-ion batteries are fully enclosed in a laser-welded, stainless steel housing.
Continental says that it, together with its waste disposal partners, is developing recycling ideas which will allow at least 50% of the content of lithium-ion cells to be recycled.
Continental started pre-series production of lithium-ion batteries last year in Berlin. The Nuremberg site, which was prepared for series production in 12 months, can produce 15,000 lithium-ion battery packs annually—this capacity can be doubled at short notice, according to the company.