Energy storage cell impedance measuring apparatus, methods and related systems

• US 9,851,414 B2
• Filed: 07/01/2015
• Issued: 12/26/2017
• Est. Priority Date: 12/21/2004
• Status: Active Grant

• Current Assignee: Battelle Energy Alliance LLC (Battelle Memorial Institute)
• Original Assignee: Battelle Energy Alliance LLC (Battelle Memorial Institute)
• Inventors: Morrison, John L, Morrison, William H, Christophersen, Jon P
• Primary Examiner(s): DIAO, M BAYE
• Application Number:
  US14/789,959
• Publication Number:
  US 20170003354A1
• Time in Patent Office: 909 Days
• Field of Search: 324430, 702 64, 702 75
• CPC Class Codes: G01R 31/382 Arrangements for monitoring battery or accumulator variables, e.g. SoC
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables

Abstract

Energy storage cell impedance testing devices, circuits, and related methods are disclosed. An energy storage cell impedance measuring device includes a sum of sinusoids (SOS) current excitation circuit including differential current sources configured to isolate a ground terminal of the differential current sources from a positive terminal and a negative terminal of an energy storage cell. A method includes applying an SOS signal comprising a sum of sinusoidal current signals to the energy storage cell with the SOS current excitation circuit, each of the sinusoidal current signals oscillating at a different one of a plurality of different frequencies. The method also includes measuring an electrical signal at a positive terminal and a negative terminal of the energy storage cell, and computing an impedance of the energy storage cell at each of the plurality of different frequencies using the measured electrical signal.

Claims

1. An energy storage cell impedance measuring device, comprising:

a sum-of-sinusoids (SOS) current excitation circuit including differential current sources configured to isolate a ground terminal of the differential current sources from a positive terminal and a negative terminal of an energy storage cell, the SOS current excitation circuit configured to apply an SOS signal through the energy storage cell, the SOS signal including a sum of a plurality of sinusoidal current signals, each of the plurality of sinusoidal current signals oscillating at a different one of a plurality of different frequencies; and

control circuitry configured to operably couple to the SOS current excitation circuit, the positive terminal, and the negative terminal, the control circuitry comprising;

an SOS control module configured to cause the SOS current excitation circuit to produce the SOS signal;

at least one signal measuring module configured to measure electrical signals on the positive terminal and the negative terminal of the energy storage cell; and

an impedance computation module configured to use the electrical signals measured by the at least one signal measuring module to compute an impedance of the energy storage cell for each frequency of the SOS signal.

2. The energy storage cell impedance measuring device of claim 1, wherein the plurality of different frequencies include integer harmonic frequencies of a lowest frequency of the plurality of different frequencies.

3. The energy storage cell impedance measuring device of claim 2, wherein the plurality of sinusoidal current signals of the SOS signals include alternating sine and cosine current signals for each successive frequency of the plurality of different frequencies.

4. The energy storage cell impedance measuring device of claim 1, further comprising a high voltage buffer operably coupled between the SOS current excitation circuit and the energy storage cell, the high voltage buffer configured to isolate at least one signal line of the SOS current excitation circuit carrying at least a portion of the SOS signal from a direct current voltage potential difference between the positive terminal and the negative terminal.

5. The energy storage cell impedance measuring device of claim 4, wherein the high voltage buffer includes a high voltage blocking capacitor operably coupled between at least one of the differential current sources and at least one of the positive terminal and the negative terminal of the energy storage cell.

6. The energy storage cell impedance measuring device of claim 1, wherein the differential current sources include a push current source configured to push current into the energy storage cell, and a pull current source configured to pull current from the energy storage cell.

7. The energy storage cell impedance measuring device of claim 6, wherein the push current source is configured to provide at least substantially a same current as the pull current source.

8. The energy storage cell impedance measuring device of claim 1, wherein the differential current sources are configured to provide the SOS signal through an energy storage cell having a direct current voltage potential output of greater than about sixty (60) volts direct current.

9. The energy storage cell impedance measuring device of claim 1, wherein the differential current sources are configured to provide the SOS signal through an energy storage cell having a direct current voltage potential output of at least about three hundred (300) volts direct current.

10. A method of measuring impedance of an energy storage cell, the method comprising:

applying, with a sum-of-sinusoids (SOS) current excitation circuit of an impedance measuring device including differential current sources configured to isolate a ground terminal of the differential current sources from a positive terminal and a negative terminal of an energy storage cell, an SOS signal to the energy storage cell, the SOS signal comprising a sum of sinusoidal current signals, each of the sinusoidal current signals oscillating at a different one of a plurality of different frequencies;

measuring an electrical signal at the positive terminal and the negative terminal of the energy storage cell with at least one signal measuring module of the impedance measuring device coupled to the positive terminal and the negative terminal; and

computing, with an impedance computation module of the impedance measuring device, an impedance of the energy storage cell at each of the plurality of different frequencies using the measured electrical signal.

11. The method of claim 10, wherein measuring an electrical signal at the positive terminal and the negative terminal with the at least one measuring module comprises:

measuring a voltage potential response to the SOS signal across the positive terminal and the negative terminal of the energy storage cell; and

measuring a current response to the SOS signal through the energy storage cell.

12. The method of claim 11, wherein computing, with an impedance computation module, the impedance of the energy storage cell at each of the plurality of different frequencies comprises dividing a portion of the measured voltage potential response that corresponds to each of the plurality of different frequencies by a portion of the measured current response that corresponds to a same one of the plurality of different frequencies.

13. The method of claim 12, wherein computing, with an impedance computation module, the impedance of the energy storage cell comprises calculating the impedance of the energy storage cell without calibrating control circuitry configured to compute the impedance of the energy storage cell.

14. The method of claim 10, further comprising calibrating, using a single shunt of known resistance, control circuitry configured to compute the impedance of the energy storage cell.

15. The method of claim 14, wherein calibrating the control circuitry comprises:

applying, with the SOS current excitation circuit, a first SOS signal having a first magnitude to the single shunt;

measuring a response of the single shunt to the first SOS signal with the at least one signal measuring module;

applying, with the SOS current excitation circuit, a first orthogonal SOS signal having the first magnitude to the single shunt; and

measuring a response of the single shunt to the first orthogonal SOS signal with the at least one signal measuring module.

16. The method of claim 15, wherein calibrating the control circuitry further comprises:

applying, with the SOS current excitation circuit, a second SOS signal having a second magnitude, different from the first, to the single shunt;

measuring a response of the single shunt to the second SOS signal with the at least one signal measuring module;

applying, with the SOS current excitation circuit, a second orthogonal SOS signal having the second magnitude to the single shunt; and

measuring a response of the single shunt to the second orthogonal SOS signal with the at least one signal measuring module.

17. The method of claim 10, wherein applying the SOS signal comprises applying, with the SOS current excitation circuit, the SOS signal for a single period of a lowest frequency of the plurality of different frequencies.

18. An energy storage cell impedance measuring circuit, comprising:

differential current sources, including;

a push current source configured to operably couple to a positive terminal of an energy storage cell;

a pull current source configured to operably couple to a negative terminal of the energy storage cell; and

a ground terminal of the differential current sources operably coupled between the push current source and the pull current source; and

a high voltage buffer operably coupled to at least one of the push current source and the pull current source and configured to isolate the at least one of the push current source and the pull current source from a direct current voltage provided by the energy storage cell;

wherein the differential current source is configured to apply a sum-of-sinusoids (SOS) signal through the positive terminal and the negative terminal of the energy storage cell.

19. The energy storage cell impedance measuring circuit of claim 18, wherein the push current source and the pull current source each include an operational amplifier current source.

20. The energy storage cell impedance measuring circuit of claim 18, wherein the high voltage buffer includes at least one capacitor operably coupled between at least one of:

the push current source and the positive terminal; and

the pull current source and the negative terminal.

21. The energy storage cell impedance measuring circuit of claim 20, wherein the high voltage buffer includes pre-charge control circuitry configured to pre-charge the at least one capacitor.

22. An impedance measuring system, comprising:

one or more energy storage cells; and

an energy storage cell impedance measuring system operably coupled to the one or more energy storage cells, the energy storage cell impedance measuring system including;

sum-of-sinusoids (SOS) current excitation circuitry including differential current sources, the SOS current excitation circuitry configured to apply SOS signals to the one or more energy storage cells, the SOS signals including sums of a plurality of sinusoidal current signals, each of the plurality of sinusoidal current signals including a different one of a plurality of different frequencies; and

control circuitry operably coupled to the SOS current excitation circuit and the one or more energy storage cells, the control circuitry configured to;

control the SOS current excitation circuitry;

measure electrical signals at terminals of the one or more energy storage cells responsive to the SOS signals; and

compute impedances of the energy storage cells.

23. The impedance measuring system of claim 22, wherein the one or more energy storage cells include a plurality of energy storage cells.

24. The impedance measuring system of claim 23, further comprising a switching network configured to selectively operably couple the energy storage cell impedance measuring system to the plurality of energy storage cells.

25. The impedance measuring system of claim 22, further comprising an automobile including the one or more energy storage cells.

26. The impedance measuring system of claim 25, wherein the automobile further includes the energy storage cell impedance measuring system.