A method for extracting the equivalent circuit parameters of a lead-acid battery from sparse (only three) impedance spectroscopy observations at three different frequencies is outlined. The method is ideal for finding the parameters in an equivalent circuit consisting of bulk resistance, a reaction resistance and a constant phase element (CPE). Electrochemical impedance spectroscopy (EIS) measurements were made on spirally wound 2.5 Ah lead-acid cells. The equivalent circuit parameters found using our method closely compare with those extracted from the EIS measurements. The complete EIS spectrum calculated using the estimated circuit parameters at all other frequencies also closely matched the actual measurements.