NON-INVASIVE METHOD OF DETERMINING THE ELECTRICAL IMPEDANCE OF A BATTERY
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Abstract
A non-invasive method and device for determining the electrical impedance of an electrochemical system for electric power is disclosed. The voltage and current are measured at terminals as a function of time, and these measurements are converted to signals dependent on frequency. The signals dependent on frequency are subjected to at least one segmentation. For each segment, a power spectral density of the current signal ΨI dependent on frequency and the cross power spectral density of the voltage and current signals ΨIV dependent on frequency are determined for each segment. The electrical impedance of the electrochemical system is determined by calculating a ratio dependent on frequency of a mean of the power spectral densities ΨI dependent on frequency to a mean of the cross power spectral densities ΨIV dependent on frequency.
12 Citations
42 Claims
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1. -13. (canceled)
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14. A method for determining electrical impedance of an electrochemical system for electric power storage, comprising:
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acquiring voltage and current signals which are a function of time at terminals of the system and converting the voltage and current signals into signals depending on frequency; processing the signals depending on frequency into segments; determining a power density of the current signal depending on frequency and a cross power spectral density of voltage and current signals depending on frequency; and determining the electrical impedance of the electrochemical system by calculating a ratio depending on frequency of a mean of the power spectral density of the current signal to a mean of the cross power spectral density of the voltage and current signals depending on frequency. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37)
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38. A device for determining complex electrical impedance of an electrochemical system providing electric power storage, comprising:
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means for measuring voltage at terminals of the system as a function of time; means for measuring current at the terminals of the system as a function of time; software, executed on a processor, which converts measurements of the voltage and current into signals depending on frequency; means for converting the signals depending on frequency into segments; software, executed on a processor, which for each segment computes a power spectral density of the measured current depending on frequency and a cross power spectral density of a voltage and current signals depending on frequency; and software, executed on a processor, which computes the electrical impedance of the electrochemical system by computing a ratio of a mean of the power spectral density of the current signal to a mean of the cross power spectral densities of the voltage and current signals depending on frequency.
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39. A system of estimating an internal state of an electrochemical system for electric power storage including a device for determining complex electrical impedance of an electrochemical system providing electrical power storage comprising:
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means for measuring voltage at terminals of the system as a function of time; means for measuring current at the terminals of the system as a function of time; software, executed on a processor, which converts measurements of the voltage and current into signals depending on frequency; means for converting the signals depending on frequency into segments; software, executed on a processor, which computes for each segment a power spectral density of the measured current depending on frequency and a cross power spectral density of a voltage and current signals depending on frequency; and software, executed on a processor, which computes the electrical impedance of the electrochemical system by computing a ratio of a mean of the power spectral density of the current signal to a mean of the cross power spectral densities of the voltage and current signals depending on frequency; a memory for storing a relation between a property related to an internal state of the electrochemical system and electrical impedance of the system; and means, utilizing the relation, for computing the property related to the internal state of the electrochemical system.
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40. A smart battery management system comprising a system for estimating an internal state including a device for determining complex electrical impedance of an electrochemical system providing electrical power storage comprising:
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means for measuring voltage at terminals of the system as a function of time; means for measuring current at the terminals of the system as a function of time; software, executed on a processor, which converts measurements of the voltage and current into signals depending on frequency; means for converting the signals depending on frequency into segments; software, executed on a processor, which computes for each segment a power spectral density of the measured current depending on frequency and a cross power spectral density of a voltage and current signals depending on frequency; and software, executed on a processor, which computes the electrical impedance of the electrochemical system by computing a ratio of a mean of the power spectral density of the current signal to a mean of the cross power spectral densities of the voltage and current signals depending on frequency; a memory for storing a relation between a property related to an internal state of the electrochemical system and electrical impedance of the system; and means, utilizing the relation, for computing the property related to the internal state of the electrochemical system.
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41. A vehicle comprising a battery and a smart battery management system including a system for estimating an internal state including a device for determining complex electrical impedance of an electrochemical system providing electrical power storage comprising:
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means for measuring voltage at terminals of the system as a function of time; means for measuring current at the terminals of the system as a function of time; software, executed on a processor, which converts measurements of the voltage and current into signals depending on frequency; means for converting the signals depending on frequency into segments; software, executed on a processor, which computes for each segment a power spectral density of the measured current depending on frequency and a cross power spectral density of a voltage and current signals depending on frequency; and software, executed on a processor, which computes the electrical impedance of the electrochemical system by computing a ratio of a mean of the power spectral density of the current signal to a mean of the cross power spectral densities of the voltage and current signals depending on frequency; a memory for storing a relation between a property related to an internal state of the electrochemical system and electrical impedance of the system; and means, utilizing the relation, for computing the property related to the internal state of the electrochemical system.
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42. A photovoltaic system for electric power storage including a system for estimating an internal state of an electrochemical system including a device for determining complex electrical impedance of an electrochemical system providing electrical power storage comprising:
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means for measuring voltage at terminals of the system as a function of time; means for measuring current at the terminals of the system as a function of time; software, executed on a processor, which converts measurements of the voltage and current into signals depending on frequency; means for converting the signals depending on frequency into segments; software, executed on a processor, which computes for each segment a power spectral density of the measured current depending on frequency and a cross power spectral density of a voltage and current signals depending on frequency; and software, executed on a processor, which computes the electrical impedance of the electrochemical system by computing a ratio of a mean of the power spectral density of the current signal to a mean of the cross power spectral densities of the voltage and current signals depending on frequency; a memory for storing a relation between a property related to an internal state of the electrochemical system and electrical impedance of the system; and means, utilizing the relation, for computing the property related to the internal state of the electrochemical system.
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Specification