Capacity measurement system for a battery with open circuit voltage detection

• US 7,557,540 B2
• Filed: 06/15/2006
• Issued: 07/07/2009
• Est. Priority Date: 01/23/2006
• Status: Active Grant

• Current Assignee: O2 Micro International Limited (O2 Micro Incorporated)
• Original Assignee: O2 Micro International Limited (O2 Micro Incorporated)
• Inventors: Kao, William, Hou, Vincent, Liu, Liusheng
• Primary Examiner(s): Ullah; Akm E
• Assistant Examiner(s): WILLIAMS, ARUN C
• Application Number:
  US11/453,606
• Publication Number:
  US 20070170893A1
• Time in Patent Office: 1,118 Days
• Field of Search: 320/134, 320/136, 324/427
• 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 31/3835 involving only voltage measurements

Abstract

A method and system for measuring the remaining capacity of a battery with open circuit voltage detection is disclosed. The method includes the steps of measuring an open circuit voltage, obtaining an initial capacity based on the open circuit voltage, initializing an accumulation counter with the initial capacity, adjusting the accumulation counter, and obtaining the remaining capacity based on the accumulation counter. The method further includes the step of calibrating the accumulation counter to eliminate accumulated error and offset resulting from the previous operation of adjusting the accumulation counter.

Claims

1. A method for measuring a remaining capacity of a battery, comprising the steps of:

measuring an open circuit voltage;

initializing an accumulation counter with an initial capacity;

calibrating the accumulation counter with a calibrating capacity;

obtaining the initial capacity and the calibrating capacity of the battery based on the open circuit voltage;

setting a first flag indicating that a host device initializes the accumulation counter;

adjusting the accumulation counter according to a discharging or charging process of the battery; and

obtaining the remaining capacity of the battery based on the accumulation counter.

2. The method of claim 1, wherein the step of measuring the open circuit voltage being executed before the battery supplies power to a load.

3. The method of claim 2, wherein the measurement of the open circuit voltage being marked with the first flag.

4. The method of claim 1, wherein the step of measuring the open circuit voltage being executed at a predetermined time after the battery intermits power supply to a load.

5. The method of claim 4, wherein the measurement of the open circuit voltage being marked with a second flag.

6. The method of claim 1, wherein the capacity of the battery being obtained from a look up table.

7. A system for measuring remaining capacity in a battery, comprising:

a battery having an open circuit voltage;

a battery monitor for monitoring the battery and measuring the open circuit voltage, the battery monitor including an accumulation counter and the battery monitor setting a first flag; and

a host device for reading the battery monitor and indicating the remaining capacity of the battery, the host device further being capable of initializing the accumulation counter with an initial capacity and calibrating the accumulation counter with a calibrating capacity,

wherein the battery monitor setting the first flag to indicate that the host device has initialized the accumulation counter, the initial capacity and the calibrating capacity being obtained based on the open circuit voltage.

8. The system of claim 7, wherein the host device further comprising a look up table.

9. The system of claim 7, wherein the open circuit voltage being measured before the system is powered on.

10. The system of claim 9, wherein the battery monitor setting the first flag to mark the open circuit voltage measurement.

11. The system of claim 7, wherein the open circuit voltage being measured at a predetermined time after the system is powered off.

12. The system of claim 11, wherein the battery monitor setting a second flag to mark the open circuit voltage measurement.

13. The system of claim 12, wherein the second flag indicating that the host device may calibrate the accumulation counter.

14. An electronic device capable of displaying remaining capacity of a battery, comprising:

a power terminal for receiving electrical power from the battery;

a battery monitor connected to the battery for detecting battery parameters, the battery monitor further including an accumulation counter for indicating a capacity status of the the battery parameters including an open circuit voltage for initializing the accumulation counter with an initial capacity and calibrating the accumulation counter with a calibrating capacity, and the battery monitor setting a first flag indicating that a host device initializes the accumulation counter;

a microprocessor for computing the remaining capacity of the battery based on the battery parameters and the capacity status of the battery obtained from the battery monitor; and

a display screen for displaying the remaining capacity of the battery.

15. The electronic device of claim 14, wherein the accumulation counter is initialized based on the open circuit voltage that is detected before the battery supplies power to the electronic device.

16. The electronic device of claim 14, wherein the accumulation counter is calibrated based on the open circuit voltage that is detected at a predetermined time after the battery intermits power supply to the electronic device.