An apparatus for determining a rate of charge/discharge, C rate, or state of charge, SOC, of a battery having unknown characteristics comprises a circuit for applying at least a two-pulse current load to said battery. A change in voltage, .DELTA.V, resulting from the application of the second or a subsequent pulse is used to determine the C rate of the battery as a function of .DELTA.V. An Open Circuit Voltage, OCV, of the battery a time interval after the completion of the application of the second or subsequent pulse is used to determine the SOC of the battery as a function of OCV.