Apparatuses and methods for testing electrochemical cells by measuring frequency response

Patent metadata

Field	Value
Publication number	US-10901044-B2
Application number	US-201816167962-A
Country	US
Kind code	B2
Filing date	Oct 23, 2018
Priority date	Jun 4, 2013
Publication date	Jan 26, 2021
Grant date	Jan 26, 2021

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 sum-of-sines (SOS) signal comprising a summation of two or more sinusoidal signals at different frequencies with a frequency step factor therebetween;
mitigating a zero-order hold delay by advancing the SOS signal by a time step to create a stimulus signal, wherein the time step comprises a time period between successive elements of a digital representation of one of the two or more sinusoidal signals;
applying the 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 stimulus signal; and
estimating the impedance of the device to be measured using a sum-of-sines analysis of the response signal.

2. The method of claim 1 , further comprising, prior to applying the stimulus signal to the device to be measured:
pre-emphasizing a magnitude of each of the two or more sinusoidal signals such that a magnitude of the response signal is substantially flat over a frequency range encompassing all of the two or more sinusoidal signals when the stimulus signal is applied to a shunt impedance; and
pre-emphasizing a phase of each of the two or more sinusoidal signals such that a phase shift of the response signal is substantially near zero when the stimulus signal is applied to the shunt impedance.

3. The method of claim 1 , further comprising calibrating a magnitude of each of the two or more sinusoidal signals before applying the stimulus signal to the device to be measured by;
applying the stimulus signal to a first shunt impedance and detecting a first response signal of the impedance measurement device with the first shunt impedance;
applying the stimulus signal to a second shunt impedance and detecting a second response signal of the impedance measurement device with the second shunt impedance;
applying the stimulus signal to a third shunt impedance and detecting a third response signal of the impedance measurement device with the third shunt impedance;
at each frequency of the two or more sinusoidal signals, combining the first response signal, the second response signal and the third response signal to determine a magnitude calibration; and
applying the magnitude calibration to each of the two or more sinusoidal signals of the stimulus signal.

4. The method of claim 3 , further comprising converting each of the first response signal, the second response signal, and the third response signal from a time domain to a frequency domain prior to the combining and wherein the combining is performed in the frequency domain using a least squares linear regression to determine the magnitude calibration.

5. The method of claim 1 , further comprising calibrating a phase of each of the two or more sinusoidal signals before applying the stimulus signal to the device to be measured by;
applying the stimulus signal including an added first phase shift to a shunt impedance and detecting a first response signal of the impedance measurement device with the shunt impedance;
applying the stimulus signal including an added second phase shift to the shunt impedance and detecting a second response signal of the impedance measurement device with the shunt impedance;
applying the stimulus signal including an added third phase shift to the shunt impedance and detecting a third response signal of the impedance measurement device with the shunt impedance;
at each frequency of the two or more sinusoidal signals, combining the first response signal, the second response signal and the third response signal to determine a phase calibration; and
applying the phase calibration to each of the two or more sinusoidal signals of the stimulus signal.

6. The method of claim 5 , further comprising converting each of the first response signal, the second response signal, and the third response signal from a time domain to a frequency domain prior to the combining and wherein the combining is performed in the frequency domain using a least squares linear regression to determine the phase calibration.

7. The method of claim 1 , further comprising calibrating the impedance measurement device before applying the stimulus signal to the device to be measured 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 stimulus signal;
applying the 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 to develop the gain corrections for each frequency of the two or more sinusoidal signals;

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 stimulus signal using the three or more phase shifts;
applying the stimulus signal to at least one of the three or more shunt impedances;
detecting a phase-calibration response signal for each of the three or more phase shifts; and
combining the phase-calibration response signals 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 stimulus signal.

8. The method of claim 1 , further comprising calibrating the impedance measurement device before applying the stimulus signal to the device to be measured by:
pre-emphasizing a magnitude and phase of each of the two or more sinusoidal signals;
applying the 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; and
using the calibration coefficients to scale a magnitude of each of the two or more sinusoidal signals to an RMS value less than or equal to the known RMS current.

9. The method of claim 8 , wherein the known RMS current is substantially 500 mA or less.

10. The method of claim 8 , wherein:
the two or more sinusoidal signals at different frequencies have some overlap and a longest frequency range is used for an act of applying the 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.

11. An impedance measurement device comprising:
a processor;
a data acquisition system; and
a sum-of-sines-generator for generating a sum-of-sines (SOS) signal comprising a summation of two or more sinusoidal signals at different frequencies with a frequency step factor therebetween; and
wherein one or more of the processor and the data acquisition system are configured to:
perform a function of the sum-of-sines-generator;
advance the SOS signal by a time step to create a stimulus signal, wherein the time step comprises a time period between successive elements of a digital representation of one of the two or more sinusoidal signals;
apply the stimulus signal to a device to be me

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