The testing of batteries linked to supercapacitors with electrochemical impedance spectroscopy: A comparison between Li-ion and valve regulated lead acid batteries

► SoC testing of Li-ion or VRLA batteries with supercapacitors at 2 F:1 Ah ratio. ► Only slight improvement in the charge capacity acceptance for Li-ion systems was observed. ► Good improvement in the charge capacity acceptance for VRLA systems. ► EIS study confirmed the role of supercapacitor at various SoC.