Multispectral impedance determination under dynamic load conditions

Patent metadata

Field	Value
Publication number	US-2020300920-A1
Application number	US-201916357865-A
Country	US
Kind code	A1
Filing date	Mar 19, 2019
Priority date	Mar 19, 2019
Publication date	Sep 24, 2020
Grant date	—

Abstract

Impedance testing devices, circuits, systems, and related methods are disclosed. A Device Under Test (DUT) is excited with a multispectral excitation signal for an excitation time period while the DUT is under a load condition from a load operably coupled to the DUT. A response of the DUT is sampled over a sample time period. The sample time period is configured such that it includes an in-band interval during the excitation time period and one or more out-of-band intervals outside of the in-band interval. A response of the DUT to the load condition during the in-band interval is estimated by analyzing samples of the response from the one or more out-of-band intervals. Adjusted samples are computed by subtracting the estimated load response during the in-band interval from the samples from the in-band interval. An impedance of the DUT is estimated by analyzing the adjusted samples.

First claim

What is claimed is:

1 . A method of measuring impedance, comprising:
exciting a device under test with a multispectral excitation signal for an excitation time period while the device under test is under a load condition from a load operably coupled to the device under test; sampling a response of the device under test over a sample time period, wherein the excitation time period is within the sample time period such that the sample time period includes an in-band interval during the excitation time period, and one or more out-of-band intervals outside of the in-band interval; estimating a load response of the device under test to the load condition during the in-band interval by analyzing samples of the response from the one or more out-of-band intervals; computing adjusted samples by subtracting the estimated load response during the in-band interval from the samples from the in-band interval; and estimating an impedance of the device under test by analyzing the adjusted samples.

2 . The method of claim 1 , wherein the excitation time period includes two excitation time periods and the one or more out-of-band intervals include an interval between the two excitation time periods.

3 . The method of claim 2 , wherein the one or more out-of-band intervals include at least one of a pre-band interval before the two excitation time periods and a post-band interval after the two excitation time periods.

4 . The method of claim 1 , wherein the excitation time period is within the sample time period such that the sample time period includes a pre-band interval immediately before the excitation time period, the in-band interval during the excitation time period, and a post-band interval immediately after the excitation time period.

5 . The method of claim 4 , further comprising determining a change in the load condition from a first load condition to a second load condition during the excitation time period, and wherein:
estimating the load response comprises:
fitting a first mathematical expression to samples of the response from the pre-band interval; and
fitting a second mathematical expression to samples of the response from the post-band interval;
computing the adjusted samples comprises:
analyzing the first mathematical expression at time points corresponding to the samples from the in-band interval before the change in the load condition to determine first adjusted samples; and
analyzing the second mathematical expression at time points corresponding to the samples from the in-band interval after the change in the load condition to determine second adjusted samples; and
analyzing the adjusted samples comprises analyzing the first adjusted samples and the second adjusted samples.

6 . The method of claim 1 , wherein:
estimating the load response comprises fitting a mathematical expression to samples of the response from the one or more out-of-band intervals; and computing the adjusted samples comprises analyzing the mathematical expression at time points corresponding to the samples from the in-band interval.

7 . The method of claim 6 , wherein fitting the mathematical expression comprises fitting an exponential expression.

8 . The method of claim 6 , wherein fitting the mathematical expression comprises using linear regression to perform curve fitting.

9 . The method of claim 6 , wherein the mathematical expression includes an adjustment factor for at least one element of the mathematical expression, the method further comprising;
performing an optimization process by varying the adjustment factor to optimize the fit of the mathematical expression to samples from the one or more out-of-band intervals; and using the optimized mathematical expression for the process of analyzing the mathematical expression.

10 . The method of claim 9 , wherein the optimization process comprises minimizing a mean-square-error of samples from the one or more out-of-band intervals relative to the mathematical expression.

11 . The method of claim 1 , further comprising using a potentiostatic mode wherein: exciting the device under test comprises applying a voltage signal; and
sampling the response of the device under test comprises sampling a current response.

12 . The method of claim 1 , further comprising using a galvanostatic mode wherein: exciting the device under test comprises applying a current signal; and
sampling the response of the device under test comprises sampling a voltage response.

13 . The method of claim 1 , wherein sampling the response of the device under test comprises sampling the response of a battery while the battery is under a charging load condition.

14 . The method of claim 1 , wherein sampling the response of the device under test comprises sampling the response of a battery while the battery is under a discharging load condition.

15 . The method of claim 1 , wherein:
exciting the device under test with the multispectral excitation signal comprises applying a sum-of-sines signal to a battery; and analyzing the adjusted samples comprises analyzing the adjusted samples with a sum-of-sines analysis.

16 . An impedance measurement system, comprising:
a signal conditioner configured for generating a multispectral excitation signal from a composed multispectral signal and applying the multispectral excitation signal to a device under test for an excitation time period; a data acquisition system configured for sampling a response of the device under test to generate measurements over a sample time period while the device under test is under a load condition from a load operably coupled to the device under test; and a computing system configured for:
generating the composed multispectral signal;
generating one or more timing indicators to create the sample time period, wherein the excitation time period is within the sample time period such that the sample time period includes an in-band interval during the excitation time period, and one or more out-of-band intervals outside of the excitation time period;
fitting a mathematical expression to the measurements during the one or more out-of-band intervals;
analyzing the mathematical expression at time points corresponding to time points of the response during the in-band interval to estimate in-band corruption correlated to a corruption of the response by the load condition;
computing adjusted samples by subtracting the estimated in-band corruption during the in-band interval from the measurements from the in-band interval; and
analyzing the adjusted samples to estimate an impedance of the device under test.

17 . The impedance measurement system of claim 16 , wherein the computing system is further configured for generating the one or more timing indicators such that the sample time period includes a pre-band interval immediately before the excitation time period, the in-band interval during the excitation time period, and a post-band interval immediately after the excitation time period.

18 . The impedance measurement system of claim 16 , wherein the computing system is further configured for generating the one or more timing indicators responsive to a condition selected from the group consisting of a pre-determined time, an event within the impedance measurement system, an event related to the device under test, detected anomalous behavior of the device under test, and a detected change in the load condition.

19 . The impedance measurement system of claim 16 , wherein the computing system is further configured for a

Assignees

• Battelle Energy Alliance Llc

Inventors

• Christophersen Jon P
• Morrison John L
• Morrison William H

Classifications

• H01M10/482

  for several batteries or cells simultaneously or sequentially · CPC title

• H01M10/48

  Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte (constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals, H01M50/569) · CPC title

• G01R31/389 Primary

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

• H01M2220/20

  Batteries in motive systems, e.g. vehicle, ship, plane · CPC title

• G01R31/392

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