A detailed review of the applicability of impedance measurement as a test of state-of-charge or state-of-health of battery cells has been performed in both scientific journals and technical conferences. The relationship between the various impedance parameters encountered in the literature has been investigated. Only studies concerning lead-acid and nickel-cadmium secondary battery cells, which are the most widely used batteries in industrial applications, have been considered. The rate capacities of the battery cells varied from 1 A h to several thousands of A h.