A battery management system (BMS) based on a digital signal processor (DSP) was designed for the nickel-metal hydride (Ni-MH) battery pack used in ISG medium hybrid electric vehicles(HEV). The BMS samples every module's voltage and the total voltage of the battery pack in a time-sharing, periodic way, with the application of complex programmable logic device and the array of photo couplers. As for the data acquisition of current and temperature, the sensor signals are converted and modified by effective hardware circuits. In the software design, these signals are filtered to acquire accurate results. On the basis of accurate data acquisition, the maximum charge power and discharge power of the battery pack are calculated by the query table-linear interpolation method. Meanwhile, the state of charge (SOC) is estimated with the application of a Kalman filter. The power state and SOC can reflect the energy state of the battery pack precisely. It is benefit for ISG HEV to distribute its energy properly.
