Non steady state energy cell impedance measurement

An energy cell complex impedance measurement apparatus, comprising:

• a signal generator configured to, when operating:
• generate a plurality of time sequences, comprising:
• a time sequence representing a repetitive signal at a characterizing frequency;
• a time sequence representing an orthogonal-phase-repetitive signal at the characterizing frequency that is ninety degrees out of phase with the repetitive signal;
• and
• at least one time sequence corresponding to a respective term of a power series polynomial, each respective term of the power series polynomial having a respective exponential value;
• apply, to an energy cell, one of an electrical current or an electrical voltage corresponding to the time sequence representing the repetitive signal;
• a signal measurement component configured to, when operating, measure, contemporaneously with application of the one of the electrical current or the electrical voltage, a time sequence of measured values of a response waveform corresponding to an other of the electrical current or the electrical voltage across the energy cell;
• a correlation processor configured to, when operating, determine a set of correlation values comprising a respective correlation value between the time sequence of measured values and each of:
• the time sequence representing the repetitive signal;
• the time sequence representing the orthogonal-phase-repetitive signal;
• and
• the at least one time sequence corresponding to a respective term of a power series polynomial;
• and
• a matrix multiply block configured to, when operating, transform the set of correlation values into a set of fitted coefficients comprising:
• a fitted repetitive coefficient corresponding to a magnitude of a repetitive signal component within the time sequence of measured values at the characterizing frequency;
• and
• a fitted orthogonal-phase-repetitive coefficient corresponding to a magnitude of an orthogonal-phase-repetitive signal component within the time sequence of measured values at the characterizing frequency that is ninety degrees out of phase with the repetitive signal component;
• and
• an impedance calculator configured to, when operating, determining an impedance of the energy cell at the characterizing frequency based on a ratio of the fitted orthogonal-phase-repetitive coefficient to the fitted repetitive coefficient.

A computer program product for measuring energy cell impedance, the computer program product comprising:

• a non-transitory computer-readable storage medium having computer-readable program code embodied therein configured to cause a computer to perform a method comprising:
• generating a plurality of time sequences, comprising:
• a time sequence representing a repetitive signal at a characterizing frequency;
• a time sequence representing an orthogonal-phase-repetitive signal at the characterizing frequency that is ninety degrees out of phase with the repetitive signal;
• and
• at least one time sequence corresponding to a respective term of a power series polynomial, each respective term of the power series polynomial having a respective exponential value;
• applying, to an energy cell, one of an electrical current or an electrical voltage corresponding to the time sequence representing the repetitive signal;
• measuring, contemporaneously with the applying, a time sequence of measured values of a response waveform corresponding to another of the electrical current or the electrical voltage across the energy cell;
• determining a set of correlation values comprising a respective correlation value between the time sequence of measured values and each of:
• the time sequence representing the repetitive signal;
• the time sequence representing the orthogonal-phase-repetitive signal;
• and
• the at least one time sequence corresponding to a respective term of a power series polynomial;
• and
• transforming the set of correlation values into a set of fitted coefficients comprising:
• a fitted repetitive coefficient corresponding to a magnitude of a repetitive signal component within the time sequence of measured values at the characterizing frequency;
• and
• a fitted orthogonal-phase-repetitive coefficient corresponding to a magnitude of an orthogonal-phase-repetitive signal component within the time sequence of measured values at the characterizing frequency that is ninety degrees out of phase with the repetitive signal component;
• and
• determining an impedance of the energy cell at the characterizing frequency based on a ratio of the fitted orthogonal-phase-repetitive coefficient to the fitted repetitive coefficient.