Abstract: An apparatus and method for the characterization of electricity-producing cells using broadband impedance spectroscopy are provided. A method includes injecting a broadband signal having a plurality of superimposed waveforms at different frequency set points across a frequency range into an electricity-producing cell. A distribution of the frequency set points is determined using a function which, for a predetermined number of frequency set points, spaces lower value frequency set points closer together and higher value frequency set points further apart so as to tune the frequency set point distribution optimally for the cell. One or both of a voltage and current response are measured, including obtaining the response at each frequency set point simultaneously. An impedance of the electricity-producing cell is calculated using the broadband signal and the response.