The high-voltage battery in the BMW ActiveHybrid 5 supplies 320 volts nominal, which is constantly stressed through energy consumption (electric driving), energy recovery (braking), and during charging. The individual cells charge at different rates, depending on the degree of aging and the manufacturing tolerance of the cells.
The different charge states are equalized by a “passive balancing” system. This requires continuous monitoring of cell voltage and temperature by Cell Supervising Sensor Units and processing of the data by a Battery Management Unit, both developed by Preh.
During passive balancing, the charge of all cells is adjusted by specifically discharging them to the level of the cell with the lowest charge. In this way, the charging of the entire battery is done uniformly and optimal battery performance is achieved.
Preh Executive Vice President R&D and Purchasing Jochen Ehrenberg said, "We see ourselves as a highly flexible development and manufacturing partner for battery management control units. This would be of particular interest to those automobile manufacturers competent in electrical drive systems that do not want to give a complete package to a system supplier."
Founded in 1919, Preh is a globally operating group of enterprises with more than 2,800 employees. Headquartered in Bad Neustadt a.d. Saale, Germany, Preh’s development and production competencies focus on vehicle interior control systems, sensor systems, electronic control units and assembly systems for the world’s leading vehicle manufacturers.
Apart from the parent manufacturing and development center in Bad Neustadt, Preh oversees manufacturing facilities in Portugal, Mexico, Romania and China, as well as a customer support center in Novi/Detroit, U.S.A. Since the end of June 2011, the Joyson Group of Ningbo/China holds 74.9 percent of Preh GmbH shares, while the remaining 25.1 percent are held by the Deutsche Beteiligungs AG and Preh management. The company achieved revenues of about €412 million in 2011. For more information, please visit: www.preh.com.