Battery healty monitor

• US 20060170397A1
• Filed: 01/28/2005
• Published: 08/03/2006
• Est. Priority Date: 01/28/2005
• Status: Active Grant

• Current Assignee: Johns Hopkins University
• Original Assignee: Johns Hopkins University
• Inventors: Carkhuff, Bliss G., Srinivasan, Rengaswamy, Zarriello, Paul R., Saffarian, Hassan M., Chalasani, Subhas, Phillips, Terry E.
• Granted Patent: US 7,554,294 B2
• Time in Patent Office: Days
• US Class Current: 320/132
• 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
• CPC Class Codes: G01R 31/392 Determining battery ageing or deterioration, e.g. state of health

Abstract

A battery health monitor (BHM) that operates as a battery-mountable full-spectrum alternating current (ac) impedance meter that facilitates monitoring a state-of-charge and a state-of-health of a battery. The BHM is used for monitoring one or more electrical parameters, e.g., impedance, of a battery. The BHM includes: a current sink coupled to the first terminal and configured to sink therefrom an oscillatory current so as to cause the battery to produce at a first terminal thereof an oscillatory voltage equal to or less than a dc operating voltage of the battery that would be present at the first terminal in the absence of the oscillatory current; and a voltage sensor configured to sense the oscillatory voltage at the first terminal.

Claims

1. A battery health monitor for monitoring one or more electrical parameters of a battery, the battery including first and second terminals of opposite polarity and configured to produce a direct current (dc) operating voltage at the first terminal, comprising:

a current sink coupled to the first terminal and configured to sink therefrom an oscillatory current so as to cause the battery to produce at the first terminal an oscillatory voltage equal to or less than the dc operating voltage that would be present at the first terminal in the absence of the oscillatory current; and

a voltage sensor configured to sense the oscillatory voltage at the first terminal.

2. The battery monitor of claim 1, further comprising control circuitry configured to generate an oscillatory current control signal, wherein the current sink is configured to sink the oscillatory current from the first terminal responsive to the oscillatory current control signal.

3. The battery monitor of claim 2, wherein the current sink comprises:

a transistor including

a control terminal having applied thereto a control terminal voltage that varies responsive to the oscillatory current control signal, and

a current path coupled between the first and second terminals and configured to sink the oscillatory current from the first terminal responsive to the control terminal voltage.

4. The battery monitor of claim 3, wherein the transistor is a Field Effect Transistor (FET), the control terminal is gate of the FET, and the current path coupled between the first and second terminals is a drain-source current path of the FET.

5. The battery monitor of claim 3, wherein the current sink further comprises a resistor connected in series with the transistor current path, the resistor and the transistor current path being connected between the first and second terminals.

6. The battery monitor of claim 5, wherein the sinking current produces across the series resistor a sense voltage proportional to a product of a magnitude of the sinking current and a resistance of the series resistor.

7. The battery monitor of claim 6, wherein the current sink further comprises:

an amplifier circuit configured to convert the current control signal to the control terminal voltage in response to the sense voltage.

8. The battery monitor of claim 7, wherein the amplifier includes:

a non-inverting input for receiving the current control signal;

an inverting input for receiving the sense voltage; and

an output coupled to the control terminal of the transistor.

9. The battery monitor of claim 2, wherein the control circuitry comprises:

a memory for storing a digitized waveform representative of the oscillatory current signal;

a controller for accessing the waveform; and

an digital-to-analog converter (DAC) for converting the accessed waveform into the current control signal.

10. The battery monitor of claim 1, wherein the voltage sensor includes an analog-to-digital converter (ADC) configured to produce a digitized signal representative of the oscillatory voltage.

11. The battery monitor of claim 10, further comprising:

a wireless transmitter coupled to the voltage sensor and configured to wirelessly transmit a signal indicative of the digitized signal representative of the oscillatory voltage.

12. The battery monitor of claim 10, further comprising a signal conditioner configured to filter and scale an amplitude of the oscillatory voltage to produce a conditioned oscillatory voltage, wherein the ADC converts the conditioned oscillatory voltage to the digitized signal.

13. The battery monitor of claim 1, wherein the oscillatory current includes at least three concurrent sinusoidal frequencies in each of at least three frequency decades.

14. The battery monitor of claim 13, wherein all of the frequencies have substantially equal amplitudes.

15. The battery monitor of claim 13, wherein the frequencies include a fundamental frequency and multiple even harmonics thereof.

16. The battery monitor of claim 13, wherein the current sink is configured to sink the oscillatory current for a period of time equal to multiple cycles of a lowest frequency among the at least three frequencies within a given frequency decade.

17. The battery monitor of claim 1, further comprising control circuitry configured to generate an oscillatory current control signal, wherein the current sink is configured to sink the oscillatory current from the first terminal responsive to the oscillatory current control signal.

18. The battery monitor of claim 1, further comprising:

a wireless transmitter coupled to the voltage sensor and configured to wirelessly transmit a signal indicative of the sensed voltage.

19. The battery monitor of claim 1, wherein the current sink is configured to sink the oscillatory current from the first terminal without raising the voltage of the first terminal above its dc operating voltage.

20. The battery monitor of claim 1, further comprising a controller configured to determine an impedance of the battery based on an apriori knowledge of the sinking current and the sensed voltage indicative of the oscillatory voltage.

21. A battery health monitor for monitoring a battery, the battery including first and second terminals of opposite polarity and configured to produce a direct current (dc) operating voltage at the first terminal, comprising:

a printed circuit board (PCB);

control circuitry constructed on the PCB;

a current sink constructed on the PCB and coupled to the control circuitry and the first terminal, wherein the control circuitry causes the current sink to sink from the first terminal an oscillatory current that causes the battery to produce at the first terminal an oscillatory voltage equal to or less than the dc operating voltage that would be present at the first terminal in the absence of the oscillatory current;

a voltage sensor constructed on the PCB and configured to sense the oscillatory voltage at the first terminal;

a transmitter, constructed on the PCB and coupled to the voltage sensor, configured to transmit a signal indicative of the sensed voltage; and

a housing configured and arranged to enclose the PCB at least partially, the control circuitry, the current sink, the voltage sensor and the transmitter.

22. The battery monitor of claim 21, wherein at least two of the control circuitry, the current sink, the voltage sensor and the wireless transmitter are constructed as one or more integrated circuits on the PCB.

23. The battery monitor of claim 21, wherein each of the control circuitry, the current sink, the voltage sensor and the wireless transmitter is configured to derive its full operating power from the battery.

24. The battery monitor of claim 21, wherein the sinking current includes at least three concurrent sinusoidal frequencies having approximately equal amplitudes and spanning at least three frequency decades.

25. The battery monitor of claim 21, wherein the battery monitor is mountable to the battery.

26. A battery health monitor for monitoring a battery, the battery including first and second terminals of opposite polarity and configured to produce a direct current (dc) operating voltage at the first terminal, comprising:

a printed circuit board (PCB);

control circuitry constructed on the PCB;

a current sink constructed on the PCB and coupled to the control circuitry and the first terminal, wherein the control circuitry causes the current sink to sink from the first terminal an oscillatory current that causes the battery to produce at the first terminal an oscillatory voltage equal to or less than the dc operating voltage that would be present at the first terminal in the absence of the oscillatory current;

a voltage sensor constructed on the PCB and configured to sense the oscillatory voltage at the first terminal;

a housing configured and arranged to enclose the PCB at least partially, the control circuitry, the current sink, the voltage sensor and the transmitter.

27. The battery health monitor of claim 26, wherein the control circuitry includes logic for determining one or more impedance-based electrical parameters of the battery based on an apriori knowledge of the sinking current and the sensed voltage indicative of the oscillatory voltage.

28. A method of monitoring one or more electrical parameters of a battery having first and second terminals of opposite polarity and configured to produce a direct current (dc) operating voltage at the first terminal, comprising:

sinking, from the first terminal, an oscillatory current so as to cause the battery to produce at the first terminal an oscillatory voltage equal to or less than the dc operating voltage that would be present at the first terminal in the absence of the oscillatory current; and

sensing the oscillatory voltage at the first terminal.

29. The method of claim 28, further comprising:

generating a current control signal, wherein said sinking current is responsive to the current control signal.

30. The method of claim 29, wherein said generating step includes:

storing a digitized waveform representative of the oscillatory current signal;

accessing the stored digitized waveform representative of the oscillatory current signal; and

converting the digitized waveform to the current control signal.

31. The method of claim 28, wherein said oscillatory sinking current includes sinking at least three concurrent sinusoidal frequencies in each of at least three decades of frequencies.

32. The method of claim 28, wherein all of the frequencies have substantially equal amplitudes.

33. The method of claim 28, further comprising performing said step of sinking and sensing while a battery operating current flows through the first and second terminals due to either a discharging or a charging of the battery.

34. The method of claim 28, further comprising performing said steps of sinking and sensing while the battery is in an open circuit condition.

35. The method of claim 28, further comprising:

determining a battery impedance based on an apriori knowledge of the sinking current and the sensed oscillatory voltage indicative of the oscillatory voltage.

36. The method of claim 35, wherein said determining step includes:

deriving a voltage frequency spectrum of the sensed oscillatory voltage;

deriving a current frequency spectrum of the sinking current; and

determining, based on the voltage and current frequency spectrums, the battery impedance as a function of frequency.

37. The method of claim 36, wherein said determining step further includes:

determining one or more further electrical parameters of the battery based on the battery impedance as a function of frequency.