Battery cell impedance measurement method and apparatus
First Claim
1. A circuit arrangement for determining impedance of a battery cell, the circuit comprising:
- a first circuit configured to generate sample values representative of a sine waveform and a cosine waveform at a target frequency and sample rate, with each period of the sine waveform including N sample values and each period of the cosine waveform including N sample values;
a second circuit coupled to an output of the first circuit and configured to input a current into the cell in response to the sample values of the cosine waveform, the current having an amplitude proportional to the sample values of the cosine waveform;
a third circuit coupled to the cell and configured to sample voltage levels across the cell resulting from the current being input into the cell, the third circuit is configured to sample voltage levels at a sample rate equal to a sample rate of the cosine waveform; and
a fourth circuit coupled to an output of the third circuit and configured to separate each voltage level sampled by the third circuit into real and imaginary components.
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Accused Products
Abstract
A circuit arrangement for determining impedance of a battery cell is provided. A first circuit is configured to generate sine and cosine waveforms having N sample values per period. A second circuit is coupled to an output of the first circuit and is configured to input a current into the cell in response to the sample values of the cosine waveform. The current has an amplitude proportional to the sample values of the cosine waveform. A third circuit is coupled to the cell and configured to sample voltage levels across the cell resulting from the current being input into the cell. A fourth circuit is coupled to an output of the third circuit and is configured to separate each voltage level sampled by the third circuit into real and imaginary components.
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Citations
19 Claims
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1. A circuit arrangement for determining impedance of a battery cell, the circuit comprising:
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a first circuit configured to generate sample values representative of a sine waveform and a cosine waveform at a target frequency and sample rate, with each period of the sine waveform including N sample values and each period of the cosine waveform including N sample values; a second circuit coupled to an output of the first circuit and configured to input a current into the cell in response to the sample values of the cosine waveform, the current having an amplitude proportional to the sample values of the cosine waveform; a third circuit coupled to the cell and configured to sample voltage levels across the cell resulting from the current being input into the cell, the third circuit is configured to sample voltage levels at a sample rate equal to a sample rate of the cosine waveform; and a fourth circuit coupled to an output of the third circuit and configured to separate each voltage level sampled by the third circuit into real and imaginary components. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for determining impedance of a battery cell, the method comprising:
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generating sine and cosine waveforms at a target frequency and sample rate, each period of each of the waveforms having N sample points; for each sample point of the cosine waveform; injecting a current having an amplitude corresponding to a value of the sample point into a battery cell; converting a voltage level across the cell from an analog to a digital value at a sample rate equal to the sample rate of the cosine waveform; and separating the digital value of the voltage into real and imaginary components; summing the real component of N digital values to determine a real component of the impedance of the battery cell; and summing the imaginary component of the N digital values to determine an imaginary component of the impedance of the battery cell. - View Dependent Claims (13, 14, 15)
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16. An energy storage cell arrangement, comprising:
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a plurality of battery cells coupled in series; and an impedance detection circuit coupled to one of the plurality of battery cells, the impedance detection circuit including; a first circuit configured to generate sample values representative of a sine waveform and a cosine waveform at a target frequency and sample rate, with each period of the sine waveform including N sample values and each period of the cosine waveform including N sample values; a second circuit coupled to an output of the first circuit and configured to input a current into the one of the plurality of battery cells in response to the sample values of the cosine waveform, the current having an amplitude proportional to the sample values of the cosine waveform; a third circuit coupled to the one of the plurality of battery cells and configured to sample voltage levels across the one battery cell resulting from the current being input into the one battery cell, the sampling voltage levels being at a sample rate equal to the sample rate of the cosine waveform; and a fourth circuit coupled to an output of the third circuit and configured to; multiply each voltage level sampled by the third circuit with the sine waveform of the first circuit to generate the imaginary component; multiply each voltage level sampled by the third circuit with the cosine waveform of the first circuit to generate the real component; sum the real component of N of the voltage levels sampled by the third circuit to determine a real component of the impedance of the one battery cell; and sum the imaginary component of the N of the voltage levels sampled to determine an imaginary component of the impedance of the one battery cell. - View Dependent Claims (17, 18, 19)
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Specification