APPARATUSES AND METHODS FOR TESTING ELECTROCHEMICAL CELLS BY MEASURING FREQUENCY RESPONSE

• US 20140358462A1
• Filed: 06/04/2014
• Published: 12/04/2014
• Est. Priority Date: 07/05/2007
• Status: Active Grant

• Current Assignee: Battelle Energy Alliance LLC (Battelle Memorial Institute)
• Original Assignee: Battelle Energy Alliance LLC (Battelle Memorial Institute), Qualtech Systems, Inc., Montana Tech of the University of Montana (University of Montana System)
• Inventors: Christophersen, Jon P., Morrison, John L., Morrison, William H., Bald, Patrick A.
• Granted Patent: US 10,379,168 B2
• Time in Patent Office: Days
• US Class Current: 702/65
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables
• CPC Class Codes: G01R 31/392 Determining battery ageing or deterioration, e.g. state of health

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.

Claims

1. A method of estimating an impedance of an electrochemical cell, comprising:

generating a stimulus signal comprising two or more sinusoidal signals at different frequencies with a frequency step factor therebetween;

advancing the stimulus signal by one time step;

applying the stimulus signal to the electrochemical cell with an impedance measurement device;

detecting a response signal of the electrochemical cell to the stimulus signal with the impedance measurement device; and

analyzing the response signal to determine an impedance of the electrochemical cell.

2. The method of claim 1, further comprising:

selectively enabling one or more shunts in the impedance measurement device to be coupled between the stimulus signal and the electrochemical cell;

pre-emphasizing a magnitude of each of the two or more sinusoidal signals before applying the 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.

3. The method of claim 1, further comprising:

selectively enabling one or more shunts in the impedance measurement device to be coupled between the stimulus signal and the electrochemical cell;

pre-emphasizing a phase of each of the two or more sinusoidal signals before applying the stimulus signal such that a phase shift of the response signal is substantially near zero.

4. The method of claim 1, further comprising:

applying the 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 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 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 and determining a least squares linear regression calibration for magnitude to be applied to each of the one or more sinusoidal signals responsive to the combination.

5. The method of claim 1, further comprising:

applying the stimulus signal to the impedance measurement device with a first phase shift and detecting a first response signal of the impedance measurement device;

applying the stimulus signal to the impedance measurement device with a second phase shift and detecting a second response signal of the impedance measurement device;

applying the stimulus signal to the impedance measurement device with a third phase shift 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 and determining a least squares linear regression calibration for phase to be applied to each of the one or more sinusoidal signals responsive to the combination.

6. A method of estimating an impedance of an electrochemical cell, comprising:

generating a stimulus signal to be applied to a battery, the stimulus signal including a summation of two or more sinusoidal signals at different frequencies with a frequency step factor therebetween; and

sampling a first voltage of the battery;

after sampling the first voltage of the battery, applying a second voltage including the stimulus signal to the battery; and

while the stimulus signal is being applied, sampling a third voltage of the battery, the third voltage corresponding to a response of the battery to the stimulus signal.

7. The method of claim 6, wherein sampling the first voltage and sampling the third voltage comprise sampling mid-range voltages.

8. The method of claim 7, wherein the mid-range voltages are substantially equal to 50 volts.

9. The method of claim 6, wherein sampling the first voltage and sampling the third voltage comprise sampling high-range voltages.

10. The method of claim 9, wherein the high-range voltages are substantially equal to 300 volts.

11. The method of claim 6, wherein applying the second voltage comprises applying a voltage at one of a mid-range voltage and a high-range voltage.

12. The method of claim 6, further comprising determining an analog difference between a voltage from the battery and a buck voltage set at substantially the same voltage as the first voltage.

13. An impedance measurement device, comprising:

a processor;

a data acquisition system;

a sum-of-sines generator for generating a stimulus signal to be applied to a battery, the stimulus signal including a summation of two or more sinusoidal signals at different frequencies with a frequency step factor therebetween; and

a preamplifier for buffering a first voltage of the battery and applying a second voltage including the stimulus signal to the battery and;

wherein one or more of the processor and the data acquisition system are configured to;

sample the first voltage of the battery;

after sampling the first voltage of the battery, enabling the preamplifier to apply the second voltage to the battery; and

while the stimulus signal is being applied, sampling a third voltage from the preamplifier, the third voltage corresponding to a response of the battery to the stimulus signal.

14. The impedance measurement device of claim 13, wherein the preamplifier is further configured to interface to the battery with the first voltage, the second voltage, and the third voltage as mid-range voltages.

15. The impedance measurement device of claim 14, wherein the mid-range voltages are substantially equal to 50 volts.

16. The impedance measurement device of claim 13, wherein the preamplifier is further configured to interface to the battery with the first voltage, the second voltage, and the third voltage as high-range voltages.

17. The impedance measurement device of claim 16, wherein the high-range voltages are substantially equal to 300 volts.

18. The impedance measurement device of claim 13, wherein the preamplifier further comprises a current driver is configured to generate current for the stimulus signal at a mid-range voltage.

19. The impedance measurement device of claim 13, wherein the preamplifier further comprises a differential amplifier is configured to determine an analog difference between a voltage from the battery and a buck voltage from the data acquisition system set at substantially the same voltage as the first voltage.

20. An impedance measurement device, comprising:

a processor;

a data acquisition system;

a sum-of-sines generator for generating a stimulus signal to be applied to a battery, the stimulus signal including a summation of two or more sinusoidal signals at different frequencies with a frequency step factor therebetween; and

a preamplifier for buffering a first voltage of the battery and applying a second voltage including the stimulus signal to the battery and;

wherein one or more of the processor and the data acquisition system are configured to;

advance the stimulus signal by one time step;

enable the preamplifier to apply the stimulus signal to an electrochemical cell;

while the stimulus signal is being applied, sample a response signal of the electrochemical cell to the stimulus signal; and

analyze the response signal to determine an impedance of the electrochemical cell.

21. The impedance measurement device of claim 20, further comprising:

one or more shunts configured to be selectively coupled between the stimulus signal and the electrochemical cell;

wherein one or more of the processor and the data acquisition system are configured to;

selectively enable at least one of the one or more shunts; and

pre-emphasize a magnitude of each of the two or more sinusoidal signals before enabling the preamplifier to apply the 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.

22. The impedance measurement device of claim 20, further comprising:

one or more shunts configured to be selectively coupled between the stimulus signal and the electrochemical cell;

wherein one or more of the processor and the data acquisition system are configured to;

selectively enable at least one of the one or more shunts; and

pre-emphasize a phase of each of the two or more sinusoidal signals before applying the stimulus signal such that a phase shift of the response signal is substantially near zero.

23. The impedance measurement device of claim 20, further comprising:

one or more shunts configured to be selectively coupled between the stimulus signal and the electrochemical cell;

wherein one or more of the processor and the data acquisition system are configured to;

selectively enable at least one of the one or more shunts to develop a first shunt impedance, enable the preamplifier to apply the stimulus signal to the one or more shunts, and detect a first response signal of the impedance measurement device;

selectively enable at least one of the one or more shunts to develop a second shunt impedance, enable the preamplifier to apply the stimulus signal to the one or more shunts, and detect a second response signal of the impedance measurement device;

selectively enable at least one of the one or more shunts to develop a third shunt impedance, enable the preamplifier to apply the stimulus signal to the one or more shunts, and detect a third response signal of the impedance measurement device; and

combine the first response signal, the second response signal and the third response signal and determine a least squares linear regression calibration for magnitude to be applied to each of the one or more sinusoidal signals responsive to the combination.

24. The impedance measurement device of claim 20, wherein one or more of the processor and the data acquisition system are configured to:

enable the preamplifier to apply the stimulus signal to the impedance measurement device with a first phase shift and detect a first response signal of the impedance measurement device;

enable the preamplifier to apply the stimulus signal to the impedance measurement device with a second phase shift and detecting a second response signal of the impedance measurement device;

enable the preamplifier to apply the stimulus signal to the impedance measurement device with a third phase shift and detecting a third response signal of the impedance measurement device;

combine the first response signal, the second response signal and the third response signal and determining a least squares linear regression calibration for phase to be applied to each of the one or more sinusoidal signals responsive to the combination.

25. A system, comprising:

one or more electrochemical cells configured as a power supply; and

an impedance measurement device, comprising;

a processor;

a data acquisition system;

a sum-of-sines generator for generating a stimulus signal to be applied to the one or more electrochemical cells, the stimulus signal including a summation of two or more sinusoidal signals at different frequencies with a frequency step factor therebetween; and

a preamplifier for buffering a first voltage of the one or more electrochemical cells and applying a second voltage including the stimulus signal to the one or more electrochemical cells and;

wherein one or more of the processor and the data acquisition system are configured to;

advance the stimulus signal by one time step;

enable the preamplifier to apply the stimulus signal to the one or more electrochemical cells;

while the stimulus signal is being applied, sample a response signal of the electrochemical cell to the stimulus signal; and

analyze the response signal to determine an impedance of the one or more electrochemical cells.

26. The system of claim 25, further comprising:

one or more shunts configured to be selectively coupled between the stimulus signal and the one or more electrochemical cells;

wherein one or more of the processor and the data acquisition system are configured to;

selectively enable at least one of the one or more shunts; and

pre-emphasize a magnitude of each of the two or more sinusoidal signals before enabling the preamplifier to apply the 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.

27. The system of claim 25, further comprising:

one or more shunts configured to be selectively coupled between the stimulus signal and the one or more electrochemical cells;

wherein one or more of the processor and the data acquisition system are configured to;

selectively enable at least one of the one or more shunts; and

pre-emphasize a phase of each of the two or more sinusoidal signals before applying the stimulus signal such that a phase shift of the response signal is substantially near zero.

28. The system of claim 25, further comprising:

one or more shunts configured to be selectively coupled between the stimulus signal and the one or more electrochemical cells;

wherein one or more of the processor and the data acquisition system are configured to;

selectively enable at least one of the one or more shunts to develop a first shunt impedance, enable the preamplifier to apply the stimulus signal to the one or more shunts, and detect a first response signal of the impedance measurement device;

selectively enable at least one of the one or more shunts to develop a second shunt impedance, enable the preamplifier to apply the stimulus signal to the one or more shunts, and detect a second response signal of the impedance measurement device;

selectively enable at least one of the one or more shunts to develop a third shunt impedance, enable the preamplifier to apply the stimulus signal to the one or more shunts, and detect a third response signal of the impedance measurement device; and

combine the first response signal, the second response signal and the third response signal and determine a least squares linear regression calibration for magnitude to be applied to each of the one or more sinusoidal signals responsive to the combination.

29. The system of claim 25, wherein one or more of the processor and the data acquisition system are configured to:

enable the preamplifier to apply the stimulus signal to the impedance measurement device with a first phase shift and detect a first response signal of the impedance measurement device;

enable the preamplifier to apply the stimulus signal to the impedance measurement device with a second phase shift and detecting a second response signal of the impedance measurement device;

enable the preamplifier to apply the stimulus signal to the impedance measurement device with a third phase shift and detecting a third response signal of the impedance measurement device;

combine the first response signal, the second response signal and the third response signal and determining a least squares linear regression calibration for phase to be applied to each of the one or more sinusoidal signals responsive to the combination.