Continental Starts Series Production of Lithium-ion Batteries for Hybrid Vehicles

NUREMBERG, September 24, 2008: Continental, the international automotive supplier, is the world's first manufacturer to start series production of lithium-ion batteries to be used in hybrid drive cars. The Powertrain Division has invested over three million euros in building up manufacturing capacity at the Nuremberg site. "This underlines Continental's claim that, by developing and manufacturing state-of-the-art drive technologies, it can contribute to a significant reduction in fuel consumption by vehicles in future and, consequently, to a reduction in CO2 emissions as well", said Dr. Karl-Thomas Neumann, Chief Executive Officer of Continental AG and head of the Powertrain Division. 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.

A generation of high-storage-capacity batteries
Compared with the battery technology currently in use in hybrid vehicles (nickel-metal hydride), lithium-ion batteries, the latest generation energy storage units, offer significantly greater storage capacity. The battery which Continental has developed weighs around 25 kilograms and requires an installation volume of some 13 liters. This allows the electric motor to boost the combustion engine by up to 19kW, making considerable fuel savings during acceleration or when starting off. The battery is charged when the vehicle brakes or decelerates, freewheeling up to a red light, for example. This regenerative braking or recuperation is controlled by the power electronics. Like the integral automatic start-stop function which automatically switches off the engine when the vehicle comes to a standstill and switches it on again when starting off, recuperation is included as part of Continental's hybrid modular system which combines all our hybrid technology expertise in a single package. The lithium-ion battery produced in Nuremberg, including the hybrid technology, will be installed as standard in the new Mercedes S400 BlueHYBRID, available from the middle of 2009. Thanks to the innovative technology, this luxury class sedan with its six-cylinder gasoline engine will achieve a consumption rate of 7.9 liters of super gasoline per 100 kilometers, equating to CO2 emissions of 190 grams per kilometer.

Highly demanding safety and assembly engineering
Using lithium-ion technology in vehicles poses particular challenges. "The battery has to operate safely and reliably for the whole of the life cycle stipulated by the vehicle manufacturer, and that's at least ten years", stresses Jörg Grotendorst, head of the Hybrid Electric Vehicles Business Unit in Continental's Powertrain Division. This is achieved by an elaborate battery management system which 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; and 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. So that cells are not permanently subjected to uneven loads, the CSC balances the charge levels of all the cells in the battery. This guarantees 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 preproduction series have been artificially aged in the course of exhaustive text cycles in order to simulate their use in vehicles over many years.

It is not just the safety and test engineering which is demanding; assembly poses its own challenges. Since the current inside the battery is not conducted via cables but along copper bus bars, a special welding process has to be used to join the bus bars. Only by using resistance welding which uses 16,000 amps is it possible to join the copper 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.

These new areas where lithium-ion batteries can be used also pose new disposal and recycling challenges. Continental is conscious of its responsibilities towards the environment and, together with its waste disposal partners, is developing innovative recycling ideas which will allow at least 50 percent of the content of lithium-ion cells to be recycled.

Production capacity of 15,000 units
Continental started preseries production of lithium-ion batteries last year in Berlin; then, in the space of twelve months, the series production equipment was planned and installed in the Nuremberg plant, at a total investment cost of around €3.3 million, creating 23 new jobs in the Production Department and related areas. 15,000 lithium-ion batteries can be produced annually in a production facility covering 300m²; and this capacity can be doubled at short notice.