Apparatuses and methods for testing electrochemical cells by measuring frequency response

Patent metadata

Field	Value
Publication number	US-10379168-B2
Application number	US-201414296321-A
Country	US
Kind code	B2
Filing date	Jun 4, 2014
Priority date	Jul 5, 2007
Publication date	Aug 13, 2019
Grant date	Aug 13, 2019

Abstract

Real-time battery impedance spectra are acquired by stimulating a battery or battery system with a signal generated as a sum of sine signals at related frequencies. An impedance measurement device can be used to interface between the battery system and a host computer for generating the signals. The impedance measurement device may be calibrated to adapt the response signal to more closely match other impedance measurement techniques. The impedance measurement device may be adapted to operate at mid-range voltages of about 50 volts and high-range voltages up to about 300 volts.

First claim

What is claimed is:

1. A method of estimating an impedance of a device to be measured, comprising:
generating a stimulus signal comprising a summation of two or more sinusoidal signals at different frequencies with a frequency step factor therebetween;
advancing the stimulus signal by one sample-time step;
applying the advanced stimulus signal to the device to be measured with an impedance measurement device;
detecting a response signal with the impedance measurement device, the response signal comprising a response of the device to be measured to the advanced stimulus signal; and
estimating the impedance of the device to be measured using a sum-of-sines analysis of the response signal; and
calibrating the impedance measurement device before applying the advanced stimulus signal by:
pre-emphasizing a magnitude and phase of each of the two or more sinusoidal signals;
applying the advanced and pre-emphasized stimulus signal to one or more shunt impedances at a known Root Mean Square (RMS) current;
detecting a current calibration response signal of the one or more shunt impedances with the impedance measurement device;
determining calibration coefficients from the current calibration response signal;
scaling the magnitude of calibration coefficients to each of the two or more sinusoidal signals to an RMS value less than or equal to the known RMS current; and
applying the calibration coefficients to each of the two or more sinusoidal signals.

2. The method of claim 1 , wherein frequency ranges of the two or more sinusoidal signals at different frequencies are predetermined.

3. The method of claim 2 , wherein:
the pre-determined frequency ranges have some overlap and a longest frequency range of the pre-determine frequency ranges is used for the act of applying the advanced and pre-emphasized stimulus signal to the one or more shunt impedances at the known Root Mean Square (RMS) current; and
the method further includes scaling the two or more sinusoidal signals to a number of frequencies that is a subset of the frequencies in the longest frequency range.

4. The method of claim 1 , wherein calibrating the impedance measurement device before applying the advanced stimulus signal further comprises:
selectively enabling one or more shunts in the impedance measurement device to be coupled to the stimulus signal; and
pre-emphasizing a magnitude of each of the two or more sinusoidal signals before applying the advanced stimulus signal such that a magnitude of the response signal is substantially flat over a frequency range encompassing all of the two or more sinusoidal signals.

5. The method of claim 1 , wherein calibrating the impedance measurement device before applying the advanced stimulus signal further comprises:
selectively enabling one or more shunts in the impedance measurement device to be coupled to the stimulus signal; and
pre-emphasizing a phase of each of the two or more sinusoidal signals before applying the advanced stimulus signal such that a phase shift of the response signal is substantially near zero.

6. The method of claim 1 , wherein calibrating the impedance measurement device before applying the advanced stimulus signal further comprises:
pre-emphasizing a magnitude of each of the two or more sinusoidal signals;
applying the advanced and pre-emphasized stimulus signal to the impedance measurement device with a first shunt impedance and detecting a first response signal of the impedance measurement device with the first shunt impedance;
applying the advanced and pre-emphasized stimulus signal to the impedance measurement device with a second shunt impedance and detecting a second response signal of the impedance measurement device with the second shunt impedance;
applying the advanced and pre-emphasized stimulus signal to the impedance measurement device with a third shunt impedance and detecting a third response signal of the impedance measurement device with the third shunt impedance;
combining the first response signal, the second response signal and the third response signal using a least squares linear regression to determine a magnitude calibration for each of the one or more sinusoidal signals; and
applying the magnitude calibration to each of the two or more sinusoidal signals of the advanced stimulus signal.

7. The method of claim 1 , wherein calibrating the impedance measurement device before applying the advanced stimulus signal further comprises:
pre-emphasizing a phase of each of the two or more sinusoidal signals;
applying the advanced and pre-emphasized stimulus signal to the impedance measurement device with a first phase shift on a shunt impedance and detecting a first response signal of the impedance measurement device;
applying the advanced stimulus and pre-emphasized signal to the impedance measurement device with a second phase shift on the shunt impedance and detecting a second response signal of the impedance measurement device;
applying the advanced stimulus and pre-emphasized signal to the impedance measurement device with a third phase shift on the shunt impedance and detecting a third response signal of the impedance measurement device;
combining the first response signal, the second response signal and the third response signal using a least squares linear regression to determine a phase calibration for each of the one or more sinusoidal signals; and
applying the phase calibration to each of the two or more sinusoidal signals of the advanced stimulus signal.

8. The method of claim 1 , wherein before applying the advanced stimulus signal to the device to be measured, the method further comprises calibrating the method by:
determining a gain correction for each frequency of the two or more sinusoidal signals using three or more shunt impedances encompassing an expected magnitude of the impedance of the device to be measured by:
pre-emphasizing a magnitude of each of the two or more sinusoidal signals in the advanced stimulus signal;
applying the advanced and pre-emphasized stimulus signal to each of the three or more shunt impedances and detecting a magnitude-calibration response signal for each of the three or more shunt impedances; and
combining the magnitude-calibration response signals with a least squares linear regression for magnitude to develop the gain corrections for each frequency of the two or more sinusoidal signals;

further calibrating the method by determining a phase correction for each frequency of the two or more sinusoidal signals using three or more phase shifts by:
pre-emphasizing a phase of each of the two or more sinusoidal signals in the advanced stimulus signal using the three or more phase shifts;
applying the advanced and pre-emphasized stimulus signal to one shunt impedance and detecting a phase-calibration response signal for each of the three or more phase shifts; and
combining the phase-calibration response signals with a least squares linear regression for phase to develop the phase corrections for each frequency of the two or more sinusoidal signals; and

applying the corresponding gain corrections and the corresponding phase corrections to each frequency of the two or more sinusoidal signals of the advanced stimulus signal.

9. The method of claim 1 , wherein the known RMS current is substantially 500 mA.

10. A method of estimating an impedance of a device to be measured, comprising:
generating a stimulus signal comprising two or more sinusoidal signals at different frequencies with a frequency step factor therebetween;
determining a final buck voltage by:
comparing a buck voltage to a bias voltage comprising a voltage of the device to be measured;
modifying the buck voltage;
continuously

Assignees

• Battelle Energy Alliance Llc

Inventors

• Christophersen Jon P
• Morrison John L
• Morrison William H
• Bald Patrick A

Classifications

• G01R31/389

  Measuring internal impedance, internal conductance or related variables · CPC title

• G01R31/392 Primary

  Determining battery ageing or deterioration, e.g. state of health · CPC title