Determining battery capacity using one or more applications of a constant power load

• US 6,313,609 B1
• Filed: 10/19/2000
• Issued: 11/06/2001
• Est. Priority Date: 10/19/2000
• Status: Expired due to Term

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Brink, Gregory D.
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): TIBBITS, PIA FLORENCE
• Application Number:
  US09/692,262
• Time in Patent Office: 383 Days
• Field of Search: 320/136, 320/132, 320/134, 320/152, 320/427, 320/430
• US Class Current: 320/132
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/386 using test-loads
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]

Abstract

A system and associated methodology for quickly and accurately determining a remaining capacity of a battery. The system measures battery terminal voltage during each application of one or more constant power loads to the battery, and compares either the measured voltage, or an internal impedance calculated from the measured voltage, with a pre-characterization of the relationship between battery capacity and battery voltage or impedance for the given battery type and operating conditions. This relationship may be obtained from data provided by the battery manufacturer, derived empirically or otherwise determined. This relationship may be represented by data stored in memory or by a mathematical function implemented in hardware, software, firmware or a combination thereof.

Claims

1. A battery capacity tester for determining a remaining capacity of a battery coupled to the tester, wherein said tester applies one or more constant power loads to the battery and compares a selected one of either a measured battery voltage or calculated battery impedance to a pre-characterized relationship between battery capacity and said selected voltage or impedance for certain battery characteristics and test conditions.

2. The battery capacity tester of claim 1,

wherein said one or more applications of a constant power load comprises one application of a predetermined constant power load, and

wherein said tester determines the remaining battery capacity based on a pre-characterized relationship between battery voltage and capacity for the battery at said one applied constant power load.

3. The battery capacity tester of claim 2, comprising:

a constant power source, coupled to the battery, configured to apply said predetermined constant power load; and

a battery characterizer configured to measure said battery voltage during said application of said predetermined constant power load, and to determine said remaining battery capacity based on said pre-characterized relationship between said measured battery voltage and battery capacity, wherein the pre-characterized relationship corresponds with batteries having similar characteristics under similar test conditions.

4. The battery capacity tester of claim 3, wherein said similar battery characteristics comprises one or more of the group consisting of battery chemistry and battery voltage rating, and wherein said similar test conditions comprises one or more of the group consisting of applied constant power load, temperature, etc.

5. The battery capacity tester of claim 3, wherein said battery characterizer comprises:

a voltage measurement device configured to measure said battery terminal voltage;

a memory having stored therein pre-characterized data associating said battery voltage and said battery capacity for a corresponding battery chemistry and applied constant power load; and

a battery capacity determinator configured to retrieve a battery capacity value from said memory based on said measured battery voltage, chemistry of the battery and said applied constant power load.

6. The battery capacity tester of claim 5, wherein said pre-characterized data also corresponds to battery temperature, and wherein said battery capacity determinator retrieves said remaining battery capacity also based on a sensed temperature of the battery.

7. The battery capacity tester of claim 6, wherein said pre-characterized data associating said battery voltage and said battery capacity is stored in a plurality of look-up tables each containing pre-characterized data for a given battery chemistry, applied constant power load and temperature.

8. The battery capacity tester of claim 7, wherein said constant power source comprises:

a load that consumes power; and

a constant power regulator coupled to the battery and said load, to control electrical connection of said load to the battery to provide said constant power load application.

9. The battery capacity tester of claim 8, wherein said battery capacity tester is implemented in a defibrillator, and

wherein said load is a bank of one or more capacitors of said defibrillator, and said constant power regulator is a capacitor charging device of said defibrillator that charges said bank of one or more capacitors such that said load draws power at said indicated power level.

10. The battery capacity tester of claim 8,

wherein said battery capacity tester is implemented in an electrotherapy device, and

wherein said load comprises one or more capacitors of the electrotherapy device, and

said constant power regulator is a capacitor charging device that charges said bank of one or more capacitors such that said load draws constant power at said indicated power level.

11. The battery capacity tester of claim 10, wherein said electrotherapy device is a defibrillator.

12. The battery capacity tester of claim 11, wherein said defibrillator is an automatic external defibrillator.

13. The battery capacity tester of claim 6, wherein said pre-characterized data associating said battery impedance and said battery capacity is stored in a plurality of look-up tables each containing pre-characterized data for a given battery chemistry, applied differences in said first and second constant power loads, and battery temperature.

14. The battery capacity tester of claim 11, wherein said battery characterizer comprises:

a computational element constructed and arranged to calculate said remaining battery capacity based on said predetermined relationship between said battery impedance and said remaining battery capacity for a given battery chemistry and said sensed ambient temperature.

15. The battery capacity tester of claim 12, wherein said computational element implements the following relationship to determine said internal battery impedance (z):

$z_{\mathrm{int}}=<br><br>\frac{v_1-v_2}{\frac{P_1}{v_1}-\frac{P_2}{v_2}}<br><br>$

where, Z is internal battery impedance, P₁ and P₂ are applied constant power levels and v1, v2 are the battery voltages measured during application of constant power loads P1 and P2, respectively.

16. The battery capacity tester of claim 3, wherein said battery characterizer comprises:

a voltage measurement device configured to measure said battery terminal voltage; and

a computational element constructed and arranged to calculate said remaining battery capacity based on said predetermined relationship between said battery voltage and said remaining battery capacity, wherein said pre-characterized relationship is a function of battery chemistry, battery temperature and said applied constant power level.

17. The battery capacity tester of claim 16, wherein said constant power source comprises:

a load that consumes power; and

a constant power regulator coupled to the battery and said load, to control electrical connection of said load to the battery to provide said constant power load application.

18. The battery capacity tester of claim 1,

wherein said one or more applications of a constant power load comprises a first application of first predetermined constant power load, and a second application of second predetermined constant power load and wherein said sensed battery voltage comprises a first battery voltage measured during said first constant power application and a second battery voltage measured during said second constant power application, and

wherein said tester determines the remaining battery capacity based on a pre-characterized relationship between internal battery impedance and battery capacity, wherein said impedance is derived from a relationship between said first and second battery voltages and said first and second applied power loads.

19. The battery tester of claim 18, wherein the battery capacity tester comprises:

a constant power source configured to apply, in two successive occurrences, said first and second predetermined constant power loads; and

a battery characterizer configured to provide said constant power source with an indication of each said predetermined constant power load and to sense said first and second battery voltages and an ambient temperature during each said first and second constant power applications, and to determine said remaining battery capacity based on said battery impedance, said ambient temperature and a battery chemistry.

20. The battery capacity tester of claim 19, wherein said battery characterizer comprises:

a voltage measurement device configured to measure said battery terminal voltage;

a memory having stored therein pre-characterized data associating said battery impedance and said battery capacity for a corresponding battery chemistry and applied constant power loads; and

a battery capacity determinator configured to retrieve a battery capacity value from said memory based on said measured battery voltage, chemistry of the battery and said applied constant power loads.

21. An electrotherapy device comprising:

an energy delivery system including one or more capacitors and a capacitor charger; and

a battery capacity tester constructed and arranged to determine a remaining capacity of a battery installed in the electrotherapy device, wherein said tester applies one or more constant power loads to the battery and compares a selected one of either a measured battery voltage and calculated battery impedance to a pre-characterized relationship between battery capacity and said selected voltage or impedance for batteries having a same chemistry and temperature as the installed battery when subject to a same constant power loads as said one or more constant power loads.

22. The electrotherapy device of claim 21,

wherein said one or more applications of a constant power load comprises one application of a predetermined constant power load, and

wherein said tester determines the remaining battery capacity based on a pre-characterized relationship between battery voltage and capacity for the battery at said one applied constant power load.

23. The electrotherapy device of claim 21,

wherein said one or more applications of a constant power load comprises a first application of first predetermined constant power load, and a second application of second predetermined constant power load and wherein said sensed battery voltage comprises a first battery voltage measured during said first constant power application and a second battery voltage measured during said second constant power application, and

wherein said tester determines the remaining battery capacity based on a pre-characterized relationship between internal battery impedance and battery capacity, wherein said impedance is derived from a relationship between said first and second battery voltages and said first and second applied power loads.

24. The electrotherapy device of claim 21, wherein said electrotherapy device is an automatic external defibrillator.

25. A method for determining remaining battery capacity of a tested battery, the method comprising the steps of:

1) receiving indications of battery chemistry and temperature;

2) applying successively a first and a second constant power load to the battery;

3) measuring first and second terminal voltages of the battery during each constant power load application performed in step

     2);

4) calculating internal battery impedance based on said applied constant power levels and said corresponding first and second measured voltages; and

5) determining remaining battery capacity based on a pre-characterized relationship of battery impedance and battery capacity for batteries having a same chemistry and temperature as the tested battery subject to same first and second power loads as said tested battery.

26. A method for determining remaining battery capacity of a tested battery, the method comprising the steps of:

1) receiving indications of battery chemistry and temperature;

2) applying a constant power load to the battery;

3) measuring a terminal voltage of the battery during said constant power load application performed in step

     2); and

5) determining remaining battery capacity based on a pre-characterized relationship of battery voltage and battery capacity for batteries having a same chemistry and temperature as the tested battery subject to same constant power load as said tested battery.