Battery management technology for an electric vehicle

Electric vehicles are expected to occupy a significant portion of the automotive market share in the near future. An electric vehicle has only an electric drive-train powered by a battery, and an electric vehicle should provide a dozens of mile driving distance with single recharge of the battery. The cost and performance of the electric vehicle is primarily determined by the battery and its management system. In this talk, we focus on one of the most promising secondary batteries, a Li-ion battery, and its management system that fulfill both cost and performance requirements. The goal of battery and its management technology is to extend the battery lifetime as well as to guarantee safe operation. We introduce key state-of-the-art solutions for the battery and management system together with an in-vehicle network technology. The battery management software is running on the top of a real-time operating system, such as OSEK, for robust operation and potability. We provide fast communication with a high-speed CAN (control-area network) among the battery management system and other vehicle electronics. The management software is designed to be reprogrammed though the CAN channel. We propose a master-slave architecture, which is scalable to accommodate more number of battery cells to manage. Monitoring Measures pack voltage, pack current and pack temperature. Reports cell voltage and cell temperature. Diagnostics Detects and reports over- and under-voltage, temperature and current. Checks leakage current using an active isolation method. Cell Balancing Provides a method for precise cell balancing. Communications Transmits measured data and diagnostic statuses over two 500 kbps CAN ports. Reprogramming Reprograms all the software components over the CAN ports for service purpose.