System and method of battery capacity reporting

• US 6,982,544 B2
• Filed: 09/16/2004
• Issued: 01/03/2006
• Est. Priority Date: 07/05/2001
• Status: Expired due to Term

• Current Assignee: Malikie Innovations Limited (Key Patent Innovations Limited)
• Original Assignee: Research In Motion Limited (Blackberry Limited)
• Inventors: Tran, Phat H.
• Primary Examiner(s): Tso, Edward H.
• Application Number:
  US10/942,546
• Publication Number:
  US 20050029988A1
• Time in Patent Office: 474 Days
• Field of Search: 320/132, 320/134, 320/135, 320/136, 320/DIG.21, 320/149, 324/427, 324/432, 324/433, 429/90, 429/100, D13/103
• US Class Current: 320/132
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/3828 using current integration
• 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 7/0048 Detection of remaining charge capacity or state of charge [SOC]

Abstract

A method and system for accurately reporting battery capacity is disclosed herein. The disclosed method and system prevent the reporting of discontinuous capacity values resulting from starting or stopping recharge cycles. The disclosed method and system prevent over or under reporting of battery capacity due to the transition between charge and discharge curves in a battery model.

Claims

1. A method for reporting an available capacity of a rechargeable battery, comprising:

reporting the available capacity of the rechargeable battery based on a measured battery voltage;

detecting a change in state of the rechargeable battery between a discharge state and a charge state;

if the detected state change is from the charge state to the discharge state, then reporting only decreases in the available capacity until another state change is detected; and

if the detected state change is from the discharge state to the charge state, then reporting only increases in the available capacity until another state change is detected.

2. The method of claim 1, wherein the available capacity is determine from the measured battery voltage using a capacity model.

3. The method of claim 2, wherein:

if the rechargeable battery is in the discharge state, then the available capacity is determined using a discharge curve from the capacity model; and

if the rechargeable battery is in the charge state, then the available capacity is determined using a charge curve from the capacity model.

4. The method of claim 1, further comprising:

if the detected state change is from the charge state to the discharge state and a determined value of the available capacity has increased from a last reported capacity, then continuing to report the last reported capacity; and

if the detected state change is from the discharge state to the charge state and the determined value of the available capacity has decreased from the last reported capacity, then continuing to report the last reported capacity.

5. The method of claim 1, wherein the determination as to whether the available capacity is increasing or decreasing is made by comparing a candidate capacity with a last reported capacity.

6. The method of claim 1, wherein the measured battery voltage is corrected based on a measured battery current and an effective serial resistance, and wherein the reported available capacity is determined based on the corrected measured battery voltage.

7. The method of claim 6, wherein the measured battery voltage is further corrected to compensate for temperature fluctuations.

8. A method for reporting an available capacity of a rechargeable battery, comprising:

reporting the available capacity of the rechargeable battery based on a measured battery voltage;

detecting a change in state of the rechargeable battery between a discharge state and a charge state;

if the detected state change is from the charge state to the discharge state, then using a fast convergence rate to report the battery available capacity if the measured battery voltage is decreasing and using a slow convergence rate to report the available battery capacity if the measured battery voltage is increasing; and

if the detected state change is from the discharge state to the charge state, then using the fast convergence rate to report the available battery capacity if the measured battery voltage is increasing and using the slow convergence rate to report the available battery capacity if the measured battery voltage is decreasing.

9. The method of claim 8, further comprising:

if the slow convergence rate is to be used to report the available battery capacity, then first determining if a target battery capacity to be reported using the slow convergence rate is within a play range of a last reported capacity, and if the target battery capacity is not within the play range, then continuing to report the last reported capacity.

10. The method of claim 8, wherein the available capacity is determine from the measured battery voltage using a capacity model.

11. The method of claim 10, wherein:

if the rechargeable battery is in the discharge state, then the available capacity is determined using a discharge curve from the capacity model; and

if the rechargeable battery is in the charge state, then the available capacity is determined using a charge curve from the capacity model.

12. The method of claim 9, wherein the play range is determined as a function of the state of the rechargeable battery and the last reported capacity.

13. The method of claim 8, wherein the measured battery voltage is corrected based on a measured battery current and an effective serial resistance, and wherein the reported available capacity is determined based on the corrected measured battery voltage.

14. The method of claim 13, wherein the measured battery voltage is further corrected to compensate for temperature fluctuations.

15. A handheld device having a system for reporting an available capacity of a rechargeable battery, comprising:

a charging subsystem configured to determining the available capacity of the rechargeable battery based on a measured battery voltage;

a user interface configured to report the available capacity;

the charging subsystem being further configured to detect a change in state of the rechargeable battery between a discharge state and a charge state;

wherein if the detected state change is from the charge state to the discharge state, then the charging subsystem being configured to report only decreases in the available capacity until another state change is detected; and

wherein if the detected state change is from the discharge state to the charge state, then the charging subsystem being configured to report only increases in the available capacity until another state change is detected.

16. The handheld device of claim 15, wherein

if the detected state change is from the charge state to the discharge state and a determined value of the available capacity has increased from a last reported capacity, then the charging subsystem being configured to continue reporting the last reported capacity;

and

if the detected state change is from the discharge state to the charge state and the determined value of the available capacity has decreased from the last reported capacity, then the charging subsystem being configured to continue reporting the last reported capacity.

17. The handheld device of claim 15, wherein the charging subsystem determines whether the available capacity is increasing or decreasing by comparing a candidate capacity with a last reported capacity.

18. A handheld device having a system for reporting an available capacity of a rechargeable battery, comprising:

a charging subsystem configured to determining the available capacity of the rechargeable battery based on a measured battery voltage;

a user interface configured to report the available capacity;

the charging subsystem being further configured to detect a change in state of the rechargeable battery between a discharge state and a charge state;

wherein if the detected state change is from the charge state to the discharge state, then the charging subsystem being configured to use a fast convergence rate to report the battery available capacity if the measured battery voltage is decreasing and to use a slow convergence rate to report the available battery capacity if the measured battery voltage is increasing; and

wherein if the detected state change is from the discharge state to the charge state, then the charging subsystem being configured to use the fast convergence rate to report the available battery capacity if the measured battery voltage is increasing and to use the slow convergence rate to report the available battery capacity if the measured battery voltage is decreasing.

19. The handheld device of claim 18, wherein if the slow convergence rate is to be used to report the available battery capacity, then the charging subsystem being configured to determine if a target battery capacity to be reported using the slow convergence rate is within a play range of a last reported capacity, and if the target battery capacity is not within the play range, then continuing to report the last reported capacity.

20. The handheld device of claim 19, wherein the play range is determined as a function of the state of the rechargeable battery and the last reported capacity.