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Method of estimating pulse response using an impedance spectrum

  • US 8,868,363 B2
  • Filed: 06/11/2010
  • Issued: 10/21/2014
  • Est. Priority Date: 06/11/2009
  • Status: Active Grant
First Claim
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1. A method of assessing a condition of an energy storage device by estimating a response to an excitation pulse, the method comprising the acts of:

  • defining a simulated pulse profile comprising a periodic train of pulses to emulate the excitation pulse;

    decomposing the simulated pulse profile by Fourier analysis to obtain Fourier series coefficients at Fourier series frequencies, the Fourier series frequencies comprising a low frequency at the frequency of the periodic train of pulses, a largest selected harmonic frequency and harmonic frequencies therebetween;

    measuring an impedance spectrum comprising measured responses of the energy storage device to a stimulus at a plurality of frequencies, wherein one or more frequencies of the plurality of frequencies is different from the Fourier series frequencies;

    estimating values for the impedance spectrum at one or more of the Fourier series frequencies when the impedance spectrum does not include a value at the one or more of the Fourier series frequencies;

    for each of the Fourier series frequencies, combining the Fourier series coefficients with either a measured value or an estimated value of the impedance spectrum at a corresponding frequency to obtain an estimated response at that corresponding frequency;

    assembling the estimated responses for each of the Fourier series frequencies into an overall time response of the energy storage device; and

    subtracting the overall time response from a bias voltage of the energy storage device to estimate the response of the energy storage device to the excitation pulse.

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