Battery Impedance Analysis Considering DC Component in Sinusoidal Ripple-Current Charging

Sinusoidal ripple-current (SRC) charging is a new charging technique that the sinusoidal current superposed with the direct current (dc) charges the battery at the frequency where the battery-alternating current (ac)-impedance reaches a minimum. However, in analyzing the effect on the SRC charging, the dc component of the SRC has not been considered until now. This paper presents a battery impedance analysis when the dc component is considered in the SRC charging. The real battery impedance is analyzed by using an electrical second-order RC battery model and overpotential voltage waveforms. The result shows that the real battery impedance is not minimized at the minimum-ac-impedance frequency. Due to this, in comparison with the constant current (CC)-constant voltage (CV) charging, the charging time, charging amount, and charging efficiency of the SRC-CV charging are not significantly different from those of the CC-CV charging. Rather, due to the ac component, the SRC-CV charging deteriorates the RMS current and maximum rising temperature by 22.5% and 18%, respectively. Also, this paper presents that the CC-CV charging using a slightly larger dc is more suitable for practical applications, since its current stress, charging time, and maximum rising temperature are improved by 2%, 9.7%, and 8.5%, respectively, in comparison with the SRC-CV charging.