Patent ID: 8868363

Claim:
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.