Abstract - In this paper the main principles and the general structure of battery monitoring and management systems (BMS) are explained. Furthermore, a newly developed, highly accurate and inexpensive data acquisition system for BMS is presented. The modular measuring system consists of two different types of monitoring units, a battery block-voltage monitoring unit and a battery current- and temperature monitoring unit. Following the discussion of the measuring hardware, a LabView realization of a universal BMS software is described in detail. Due to the flexible design of the LabView BMS, the system is able to perform control and surveillance activities for any kind of battery application and battery technology (e.g. Pb, VRLA, NiCd, NiMH etc.). The BMS was originally designed for VRLR batteries in uninterruptible power supply systems (UPS), but was also tested in electric vehicles (VW CityStromer, BMW). In a second step, a universal battery management system (BMS) was realized as a LabView application. The use of a personal computer instead of a microcontroller leads to much higher flexibility of the BMS and allows easy adaptation to various kinds of battery applications and battery technologies. The LabView-based BMS controls data acquisition, performs data processing, visualization and storage and provides a graphic user interface. Apart from monitoring features, the BMS evaluates the measured data and interacts with external components, such as the charger, the temperature regulation system and the inverter controller. A modem battery management system, in contrast to simple battery monitors, is capable of actively affecting battery operation. Before the presentation of the new measuring hardware and the LabView-based battery management system, the main principles and general structure of a BMS are discussed.
Strong requirements concerning battery life-time, reliability and energy-efficiency are imposed on modem battery applications, e.g., on batteries in unintermptible power supply systems (UPS) or batteries in electric vehicles (EV). These high demands can only be met by employing sophisticated battery monitoring and management systems. At present, battery users (e.g. in telecommunication energy supply or in power stations) know too little about the state of their batteries to draw economically optimized decisions concerning maintenance and replacement. The employment of a battery monitoring and management system helps finding the right time for battery maintenance and replacement and, in addition, will lengthen the service intervals due to taking active influence on battery operation.
GENERAL STRUCTURE OF A BMS
Fig. 1 shows the general structure of a battery management system and divides the tasks to be performed into logical blocks [2, 8, 91. Battery management systems require battery data (battery block-voltages, current and temperature) and environmental data (temperature). Furthermore, application depending system data is needed. To obtain these values, a specialized data acquisition system is used. An example of a suitable data acquisition system for BMS is pre1. sented in chapter 1 1 The following logical block of a BMS (see Fig. 1) performs the data processing. Apart from decoding the transmitted measured values, this block calculates battery quantities (e.g. entire battery voltage, average battery temperature, etc.), integrates quantities like the battery current and performs statistical analysis (e.g. distribution of block voltages, deviation of block voltages from the average block voltage, etc.). Furthermore,...