Method to determine capacity of a battery

• US 6,441,587 B2
• Filed: 03/29/2001
• Issued: 08/27/2002
• Est. Priority Date: 03/30/2000
• Status: Expired due to Term

• Current Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Inventors: Suzuki, Katsuhiro, Okada, Tetsuya, Kurihara, Toshitake
• Primary Examiner(s): Toatley, Gregory
• Assistant Examiner(s): TIBBITS, PIA FLORENCE
• Application Number:
  US09/820,192
• Publication Number:
  US 20010054879A1
• Time in Patent Office: 516 Days
• Field of Search: 324/426-428, 324/433, 320/132, 320/148, 320/136
• US Class Current: 320/136
• CPC Class Codes: G01R 31/3828 using current integration
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]

Abstract

This method to determine capacity of a battery computes capacity in current value and then converts it into capacity in power value, or computes capacity in power value and then converts it into current value. This method to determine capacity of a battery detects either discharge current or charge current or both, and computes capacity of battery in current value, which is then converted into capacity in power value by way of multiplication by the correcting constant which varies in accordance with capacity in current value. This method to determine capacity of a battery detects battery voltage or detects either discharge current or charge current or both of the battery, then computes battery capacity in power value, and converts capacity in power value so computed into capacity in current value by way of multiplication by the correcting constant which varies in accordance with capacity in power value.

Claims

1. A method to determine capacity of a battery, comprising:

(1) detecting at least one of discharge current value and charge current value of the battery from a prescribed capacity state of the battery;

(2) computing remaining battery capacity in current value, being units of quantity of electricity, based on the detected current value; and

(3) computing remaining battery capacity in power value, being units of electrical energy, by converting the computed remaining battery capacity in current value using a selected one of a plurality of correcting constants that vary in accordance with the computed remaining battery capacity in current value.

2. A method to determine capacity of a battery according to claim 1, wherein the remaining battery capacity in current value is computed based on the detected discharge current and then the remaining capacity in power value is computed by multiplying the remaining battery capacity in current value by the selected correcting constant.

3. A method to determine capacity of a battery according to claim 2, wherein the remaining battery capacity is relative remaining battery capacity.

4. A method to determine capacity of a rechargeable battery according to claim 3, wherein the (3) computing step further comprises determining the plurality of correcting constants comprising:

(1) discharging a fully charged battery at a constant current till the remaining battery capacity relative state of charge (RSOC) measures n % of a fully charged battery capacity, at which the relative remaining capacity of the battery in current value is n %;

(2) detecting m % of discharge power by complete discharging the battery at the n % RSOC in current value using a constant power without recharging, wherein the detected m % is a corresponding relative remaining battery capacity RSOC in power value; and

(3) calculating m/n as the selected correcting constant at n % remaining battery capacity RSOC in current value.

5. A method to determine capacity of a battery according to claim 1, wherein current flowing to and from the battery is detected by a consumed current/voltage detector which is electrically connected to the battery.

6. A method to determine capacity of a battery according to claim 5, wherein output voltage of the consumed current/voltage detector is A/D converted into digital single and then the remaining battery capacity in current value is computed and corrected by using the digital signals.

7. A method to determine capacity of a battery according to claim 1, wherein the remaining battery capacity is computed by reducing either a FCC (Full Charge Capacity), which signifies a fully charged battery capacity, or a design capacity of the battery by a consumed current.

8. A method to determine capacity of a battery according to claim 1, wherein the detected current value is based on one of a fully charged capacity and a design capacity of the battery, and wherein the units of quantity of electricity are amp-hour and the units of electrical energy are watt-hour.

9. A method to determine capacity of a battery comprising:

(1) detecting battery voltage and at least one of discharge current and charge current of a battery;

(2) computing remaining battery capacity in power value (units of electrical energy);

(3) computing remaining battery capacity in current value (units of quantity of electricity) by multiplying the computed remaining battery capacity in power value by a correcting constant that varies in accordance with remaining battery capacity in power value.

10. A method to determine capacity of a battery according to claim 9, wherein the remaining capacity in power value is calculated from a detected discharge power.

11. A method to determine capacity of a battery according to claim 10, wherein the computed remaining battery capacity is relative state of charge remaining capacity.

12. A method to determine capacity of a battery according to claim 10, wherein the relative remaining battery capacity is computed by subtracting consumed power either from a fully charged battery capacity (FCC), or from design capacity.

13. A method to determine capacity of a battery according to claims 9 wherein current flowing to or from the battery is detected by a consumed current/voltage detector that is electrically connected to the battery.

14. A method to determine capacity of a battery according to claim 13 wherein output voltage of the voltage detector and the consumed current/voltage detector is A/D converted into digital signals and then the remaining battery capacity is computed and corrected by using the digital signals.

15. A method to determine capacity of a rechargeable battery according to claim 9, further comprising determining the correcting constant, wherein determining the correcting constant comprises:

(1) discharging a fully charged battery at a constant current till the remaining battery capacity relative state of charge (RSOC) measures n %, at which the relative remaining capacity of the battery in current value is n %;

(2) detecting m % of discharge power by complete discharging the battery at the n % RSOC in current value using a constant power without recharging, wherein the detected m % is a corresponding relative remaining battery capacity RSOC in power value; and

(3) calculating n/m as the correcting constant at n % remaining battery capacity RSOC in power value.

16. A method to determine capacity of a battery according to claim 9, wherein the detected current value is based on one of a fully charged capacity and a design capacity of the battery, and wherein the units of quantity of electricity are amp-hour and the units of electrical energy are watt-hour.

17. A method to determine capacity of a battery pack, comprising:

(1) detecting consumed current of the battery and converting the detected consumed current into corresponding voltage at a consumed current/voltage detector;

(2) detecting voltage of battery at a voltage detector;

(3) converting analogue signals outputted by the consumed current/voltage detector into digital signals at a first A/D converter;

(4) converting analogue signals outputted by the voltage detector into digital signals at a second A/D converter;

(5) determining either consumed electric power of the battery, which is based on the digital signals of the first A/D converter, and the second A/D converter or consumed current based on the digital signals output by the first A/D converter using a multiplier;

(6) detecting a discharge termination voltage based on the digital signals outputted at the second A/D converter by using a low battery detector;

(7) generating trigger signals for converting the analogue signals into the digital signals for transmission to the first A/D converter and the second A/D converter at prescribed intervals by using a timer;

(8) computing remaining battery capacity by subtracting either the consumed current or the consumed electric power from fully charged capacity by using a remaining capacity calculator;

(9) converting either the remaining battery capacity computed at the remaining capacity calculator or a multiplication result signal outputted at the multiplier from current value into power value, or power value into current value, by using a converter; and

(10) transmitting the remaining capacity to an electronic device.

18. A method to determine capacity of a battery pack cited in claim 17, wherein the battery pack is connected to the electronic device via a data bus.

19. A method to determine capacity of a battery pack cited in claim 17, wherein the consumed current/voltage detector outputs electric current of the battery as output voltage from a differential amplifier.

20. A method to determine capacity of a battery pack according to claim 17, wherein converting the remaining battery capacity in current value into power value comprises:

(1) inputting a relative remaining capacity in current value from the remaining capacity calculator into the converter;

(2) determining a correcting constant for the relative remaining capacity in current value inputted at the converter; and

(3) converting into the relative remaining capacity in power value by multiplying the relative remaining capacity in current value by the correcting constant.

21. A method to determine capacity of a battery according to claim 17, wherein converting the remaining battery capacity in power value into the remaining battery capacity in current value comprises:

(1) communicating the remaining battery capacity in power value to the converter from the remaining capacity calculator;

(2) selecting at the converter, the correcting constant for a relative remaining battery capacity so communicated; and

(3) multiplying the relative remaining battery capacity in power value by the correcting constant to convert the relative remaining battery capacity in power value into the relative remaining battery capacity in current value.

22. A method to determine capacity of a battery, comprising:

detecting remaining battery capacity of the battery in one of units of quantity of electricity and units of electrical energy;

determining one of a plurality of correcting constants corresponding to the detected remaining battery capacity; and

converting the detected remaining battery capacity from said one of units of quantity of electricity and units of electrical energy to the other of said units of quantity of electricity and units of electrical energy by multiplying the detected remaining battery capacity by the determined one of the plurality of correcting constants or its reciprocal.

23. A method to determine capacity of a battery according to claim 22, wherein the converted remaining battery capacity is an absolute state of charge (ASOC) remaining battery capacity calculated using a detected full charge capacity (FCC) and a design capacity (DC) of the battery.

24. A method to determine capacity of a battery according to claim 22, wherein the converted remaining battery capacity is a relative state of charge (RSOC) remaining battery capacity calculated using a detected full charge capacity (FCC).

25. A method to determine capacity of a battery according to claim 22, wherein the determining step comprises:

(1) discharging a fully charged battery at a constant current till a remaining battery capacity relative state of charge (RSOC) measures n %, at which the relative remaining capacity of the battery in current value is n %;

(2) detecting m % of discharge power by complete discharging the battery at the n % RSOC in current value using a constant power without recharging, wherein the detected m % is a corresponding relative remaining battery capacity RSOC in power value; and

(3) calculating m/n as the correcting constant at n % remaining battery capacity RSOC in current value.