LC Resonant Battery Equalizer

Switch-capacitor battery equalizer (SCBE) is widely used because of its simple structure, small PCB area, and no inductance components. Its balance current is sawtooth or trapezoid waveform is significantly different from traditional charger's DC waveform. From many non-DC charging literatures, it can be found that different frequency and waveform shape will cause the significantly different battery charging performance. Therefore, this paper explores the near-optimal balance current frequency and waveform shape of the SCBE from electrochemical impedance to optimize its battery balance performance. Further, the LC resonant battery equalizer (LC-RBE) is proposed to perform battery balancing with a sine wave. Experiments have shown that the better efficiency and lower battery temperature rise are obtained when the LC-RBE work with the battery minimum ac impedance frequency.