Thorsten Baumhöfer

Specialized battery emulator for automotive electrical systems

Complexity of the automotive electrical power system is continuously increasing. Greater amount of higher loads is added and active energy management is being introduced. The whole design of such power systems depends on the batteries being used. Since safety-related systems also need power to function, special care has to be taken considering voltage quality. However, there are a lot of parameters that can be modified, and all configurations need to be tested. Since testing is time consuming, the right tools must be used during different phases of the design process. Specialized battery emulator is a combination of a power electronics device with an advanced battery model. It is used for testing and verification of the vehicle electrical system at various battery behavior or ambient conditions. Design requirements for the hardware were identified by observing occurring current and voltage ranges as well as considering special needs in the automotive environment.

Diversion of Aging of Battery Cells in Automotive Systems

Automotive battery systems for hybrid or full battery electric vehicles have a voltage level of up to 400 V and therefore consist of a vast serial connection of battery cells. Hence, the worst cell in the string defines the overall pack performance and lifetime. A fact nowadays mostly neglected in system design is the spread in cell aging and also their initial behavior due to the production process, the cooling gradient and the position within the pack. This paper will show that it is mandatory to consider the diversification of the cells in system layout and packaging to optimize the lifetime on system level tremendously. Results of aging experiments with hundreds of cells regarding pack architectures under laboratory and therefore comparable conditions are given.