High-Resolution Converter for Battery Impedance Spectroscopy

Monitoring the condition of a battery is beneficial in many applications. The internal impedance of the battery can be used to monitor battery health. The power converter for interfacing the battery bank can be used to measure battery impedance instead of using any dedicated commercial equipment, thus reducing system cost significantly. However, the power converter has some additional requirements in terms of control and power circuit to be able to measure battery impedance. This work analyzes the power circuit requirements and describes possible methods to meet them. These additional measures are necessary when the power level is medium or high. Advantages and disadvantages of each method are discussed. Among the suggested methods, the in-built phase-locked loop of field programmable gate array for enhancing pulse-width modulation (PWM) resolution and an interleaved PWM converter circuit approach are used to successfully measure battery impedance with a 3 kW converter. Requirements for the measurement circuit are also discussed and a suitable measurement circuit is proposed.