DISCHARGING BATTERIES

• US 20100201320A1
• Filed: 02/09/2010
• Published: 08/12/2010
• Est. Priority Date: 02/09/2009
• Status: Active Grant

• Current Assignee: Aggreko LLC (Aggreko Ltd.)
• Original Assignee: Xtreme Power
• Inventors: Coe, Carlos, Hurst, Aeron
• Granted Patent: US 8,847,551 B2
• Time in Patent Office: Days
• US Class Current: 320/129
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H01M 10/48 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 Class Codes: H02J 7/0069 Charging or discharging for charge maintenance, battery initiation or rejuvenation
• CPC Class Codes: H02J 7/0071 with a programmable schedule
• CPC Class Codes: H02J 7/00711 with introduction of pulses during the charging process
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

Discharging a battery is accomplished by: applying an electrical stimulus to the battery; measuring a response to the electrical stimulus, the measured response providing an indication of discharge efficiency of the battery; determining a target frequency corresponding to a maximum discharge efficiency; and then discharging the battery with a discharge current profile comprising current pulses having a frequency component selected based on the determined target frequency.

Claims

1. A method of discharging a battery, the method comprising:

applying an electrical stimulus to the battery;

measuring a response to the electrical stimulus, the measured response providing an indication of discharge efficiency of the battery;

determining a target frequency corresponding to a maximum discharge efficiency; and

then

discharging the battery with a discharge current profile comprising current pulses having a frequency component selected based on the determined target frequency.

2. The method of claim 1, wherein the electrical stimulus is a transient signal, a flat power spectral density within a fixed bandwidth at a predetermined center frequency, or a discharge pulse signal having a discharge pulse frequency.

3. The method of claim 1, wherein the electrical stimulus is a discharge pulse signal having a discharge pulse frequency, and applying the electrical stimulus to the battery comprises sweeping the discharge pulse frequency over a frequency sweep range from an initial pulse frequency to a maximum pulse frequency.

4. The method of claim 1, wherein the measured response is a rate of change in voltage, a dynamic internal impedance, or a frequency response.

5. The method of claim 1, wherein the discharge current profile further comprises a base current having a base current magnitude, and wherein the current pulses are superimposed on the base current.

6. The method of claim 5, wherein the base current magnitude is dependent on the measured response.

7. The method of claim 3, wherein measuring the response comprises:

measuring a change in voltage of the battery over a predetermined period of time while the discharge pulse frequency is swept over the frequency sweep range; and

calculating, based on the measured change in voltage, a rate of change in voltage.

8. The method of claim 3, wherein measuring the response comprises:

measuring a voltage of the battery;

measuring a current flowing through the battery; and

calculating, based in part on the measured voltage and current, an internal dynamic impedance of the battery;

wherein the voltage and the current are measured while the discharge pulse frequency is swept over the frequency sweep range.

9. The method of claim 5, wherein the method further comprises adjusting the base current magnitude based on the measured response.

10. The method of claim 1, wherein the battery is one of several interconnected batteries of a battery pack.

11. The method of claim 10, wherein the current pulses comprise different frequency components selected based on determined target frequencies of different batteries of the battery pack.

12. The method of claim 1, wherein the frequency component selected based on the determined target frequency is the determined target frequency, or a harmonic thereof.

13. A battery power transfer system comprising:

control circuitry coupled to a charge/discharge module, the control circuitry configured to cause the charge/discharge module to apply an electrical stimulus to a battery and to determine, based at least in part on a measured response of the battery to the applied stimulus, a target power transfer frequency of the battery;

wherein power is transferred from the battery with a power transfer profile comprising current pulses having a frequency component selected based on the determined target power transfer frequency.

14. The system of claim 13, wherein the measured response is a rate of change in voltage, a dynamic internal impedance, or a frequency response.

15. The system of claim 13, further comprising measurement circuitry coupled with the control circuitry to provide the measured response of the battery.

16. The system of claim 15, wherein the measurement circuitry comprises an optically-isolated voltage detector.

17. The system of claim 15, wherein the measurement circuitry comprises a spectrum analyzer.

18. The system of claim 13, wherein the electrical stimulus is a discharge pulse signal having a pulse frequency, and the charge/discharge module sweeps the pulse frequency over a frequency sweep range from an initial pulse frequency to a maximum pulse frequency.

19. The system of claim 13, wherein the charge/discharge module is a bidirectional power supply.

20. The system of claim 13, wherein the power transfer profile further comprises a base current having a base current magnitude, and wherein the current pulses are superimposed on the base current.

21. The system of claim 13, wherein the base current magnitude is variable, and wherein the control circuitry is configured to adjust the base current magnitude dependent on the measured response.

22. The system of claim 13, wherein the battery is one of several interconnected batteries of a battery pack of the system.

23. The system of claim 22, wherein the current pulses comprise different frequency components selected based on determined target power transfer frequencies of different batteries of the pack.

24. The system of claim 13, wherein the frequency component selected based on the determined target power transfer frequency is the determined target power transfer frequency, or a harmonic thereof.