Development and verification of impedance measurement equipment of high-voltage battery pack

Since the impedance of a battery is an important variant that can be used to estimate the state of the battery, such as the state of charge, current life expectancy, and remaining capacity, an accurate measurement of impedance is required, and the significance of impedance measurement becomes more pronounced when it comes to high-voltage battery packs, which are composed of numerous cells. However, previous studies have been developed focusing only on cells or low-voltage packs, making it difficult to find any study that can help measure the impedance of high-voltage battery packs, which are primarily used for electric vehicles/hybrid electric vehicles. Accordingly, this paper presents an impedance measurement system required to diagnose the state of high-voltage battery packs. Although the proposed system has low measurement accuracy, it uses data acquisition board, which can receive a wide range of voltage, and applies a digital lock-in amplifier to complement the measurement accuracy. The validity of the developed system is verified through the verification test of the reference board and the impedance measurement of high-voltage battery packs used for HEVs