Method and apparatus for determining battery properties from complex impedance/admittance
First Claim
1. Apparatus for determining an electrical, chemical, or physical property of an electrochemical cell or battery comprising:
- measuring circuitry adapted to couple to said cell or battery and adapted to determine a real part and an imaginary part of complex immittance of said cell or battery at a measurement frequency;
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 determine said electrical, chemical, or physical property from one or more values of said elements.
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Abstract
A device includes a microprocessor or microcontroller and measures real and imaginary parts of complex immittance of a cell or battery at n discrete frequencies, where n is an integer number equal to or greater than 2. The device determines cell/battery properties by evaluating components of an equivalent circuit model comprising 2n frequency-independent elements. Equating real and imaginary parts of measured immittance to values appropriate to the model at the n measurement frequencies defines a system of 2n nonlinear equations. Introducing 2n intermediate variables permits solving these equations and leads to values for the 2n model elements. A table of element values contains virtually the same information as the spectrum of complex immittance over a wide frequency range but provides this information in a more concise form that is easier to store, analyze, and manipulate. Thus, the 2n element values may themselves comprise the desired result. If desired, however, a predetermined relationship between one or more of the elements and an additional electrical, chemical, or physical property of the cell/battery may be further invoked to determine the additional property.
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Citations
25 Claims
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1. Apparatus for determining an electrical, chemical, or physical property of an electrochemical cell or battery comprising:
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measuring circuitry adapted to couple to said cell or battery and adapted to determine a real part and an imaginary part of complex immittance of said cell or battery at a measurement frequency;
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 determine said electrical, chemical, or physical property from one or more values of said elements. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. Apparatus for assessing the ability of an electrochemical cell or battery to supply current to a load comprising:
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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. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A method for determining an electrical, chemical, or physical property of an electrochemical cell or battery comprising:
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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. - View Dependent Claims (15, 16, 17, 18, 24)
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19. A method for determining the ability of an electrochemical cell or battery to supply current to a load comprising:
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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. - View Dependent Claims (20, 21, 22, 23, 25)
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Specification