Method and apparatus for determining battery properties from complex impedance/admittance

Apparatus for assessing the ability of an electrochemical cell or battery to supply current to a load comprising:

• measuring circuitry adapted to couple to said cell or battery and adapted to pass a periodic current through said cell or battery, to sense a periodic voltage across said cell or battery, and to determine a real part and an imaginary part of complex immittance of said cell or battery at a measurement frequency comprising a component frequency of said periodic current and said periodic voltage;
• control circuitry coupled to said measuring circuitry and adapted to command said measuring circuitry to select each one of n said measurement frequencies thereby defining n said real parts, n said imaginary parts and n said measurement frequencies where n is an integer number equal to or greater than two;
• and,
• computation circuitry coupled to said measuring circuitry and to said control circuitry and adapted to numerically combine values of said n real parts, said n imaginary parts, and said n measurement frequencies to evaluate one or more elements of a 2n-element equivalent circuit model and further adapted to assess said ability from values of one or more said elements.

A method for determining an electrical, chemical, or physical property of an electrochemical cell or battery comprising:

• measuring real and imaginary parts of complex immittance of said electrochemical cell or battery at n discrete frequencies where n is an integer number equal to or greater than two;
• evaluating linear electrical elements of an equivalent circuit model of said electrochemical cell or battery from said n discrete frequencies and said complex immittance at said n discrete frequencies, said circuit model comprising an interconnection of 2n linear electrical elements;
• and,
• determining said electrical, chemical, or physical property of said electrochemical cell or battery from values of one or more said linear electrical elements.

A method for determining the ability of an electrochemical cell or battery to supply current to a load comprising:

• measuring real and imaginary parts of complex immittance of said electrochemical cell or battery at n discrete frequencies where n is an integer number equal to or greater than two;
• evaluating linear electrical elements of an equivalent circuit model of said electrochemical cell or battery from said n discrete frequencies and said complex immittance at said n discrete frequencies, said circuit model comprising an interconnection of 2n linear electrical elements;
• and,
• determining said ability of said electrochemical cell or battery to supply current to a load from values of one or more of said linear electrical elements.