TRACKING FADING BATTERY CAPACITY IN A PLUGGED-IN PORTABLE ELECTRONIC DEVICE

• US 20140257724A1
• Filed: 03/08/2013
• Published: 09/11/2014
• Est. Priority Date: 03/08/2013
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Mattisson, Nils E., Ungar, P. Jeffrey, Greening, Thomas C., Koller, Jeffrey G.
• Granted Patent: US 9,506,987 B2
• Time in Patent Office: Days
• US Class Current: 702/63
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/3828 using current integration
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• 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: H01M 2220/30 Batteries in portable systems, e.g. mobile phone, laptop
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A system for tracking the capacity of a battery in a portable electronic device is described. While the portable electronic device remains plugged in to a power adapter, the system estimates the capacity of the battery by performing the following operations. The system measures a first open-circuit voltage for the battery while the battery rests at a first state of charge. Next, the system causes the battery to transition to a second state of charge. While the battery transitions to the second state of charge, the system integrates a current through the battery to determine a net change in charge for the battery. Next, the system measures a second open-circuit voltage for the battery while the battery rests at the second state of charge. Finally, the system estimates a capacity for the battery based on the first open-circuit voltage, the second open-circuit voltage and the net change in charge. This capacity measurement is repeated and the multiple results are fit to a line. The slope of fitted line is then used to estimate how the true battery capacity has faded since last measured using traditional methods that require the battery to be rested at a low state of charge.

Claims

1. A method for tracking a capacity of a battery in a portable electronic device, comprising:

while the portable electronic device remains plugged in to a power adapter that provides electrical power from a wall outlet, estimating the capacity of the battery by,

performing a first open-circuit voltage measurement on the battery while the battery rests at a first state of charge,

causing the battery to transition to a second state of charge while the portable electronic device remains plugged in to the power adapter,

while the battery is transitioning to the second state of charge, monitoring a current through the battery to determine a net change in charge for the battery,

performing a second open-circuit voltage measurement on the battery while the battery rests at the second state of charge, and

calculating the estimate for the capacity of the battery based on the first open-circuit voltage measurement, the second open-circuit voltage measurement and the net change in charge.

2. The method of claim 1, wherein the method further comprises:

repeating a process of estimating the capacity of the battery at multiple times to generate multiple estimates for the capacity of the battery; and

using the multiple estimates to produce a more-accurate estimate for the capacity of the battery.

3. The method of claim 2, wherein using the multiple estimates to produce a more-accurate estimate for the capacity of the battery comprises:

using the multiple estimates to determine a capacity-change trend for the battery; and

applying the capacity-change trend to a reference measurement for the capacity of the battery obtained while the portable electronic device was not plugged in to a power adapter to produce the more-accurate estimate for the capacity of the battery.

4. The method of claim 3, wherein determining the capacity-change trend comprises fitting the multiple estimates generated at multiple times to a linear function.

5. The method of claim 3, wherein determining the capacity-change trend comprises fitting the multiple estimates generated at multiple times to a second-order function.

6. The method of claim 1,

wherein the first state of charge is higher than the second state of charge;

and

wherein causing the battery to transition from the first state of charge to the second state of charge involves powering the portable electronic device from the battery and not the power adapter while the portable electronic device is drawing current.

7. The method of claim 6,

wherein the first state of charge is a fully charged state for the battery;

and

wherein the second state of charge is within 5% of the fully charged state of the battery.

8. The method of claim 1,

wherein the second state of charge is higher than the first state of charge;

and

wherein causing the battery to transition from the first state of charge to the second state of charge involves charging the battery using current supplied by the power adapter.

9. A system for tracking a capacity of a battery in a portable electronic device, comprising:

the portable electronic device;

the battery contained within the portable electronic device;

wherein the portable electronic device is configured to connect to a power adapter that provides electrical power from a wall outlet; and

a controller within the portable electronic device configured to estimate the capacity of the battery by,

performing a first open-circuit voltage measurement on the battery while the battery rests at a first state of charge,

causing the battery to transition to a second state of charge while the portable electronic device remains plugged in to the power adapter,

while the battery is transitioning to the second state of charge, monitoring a current through the battery to determine a net change in charge for the battery,

performing a second open-circuit voltage measurement on the battery while the battery rests at the second state of charge, and

calculating the estimate for the capacity of the battery based on the first open-circuit voltage measurement, the second open-circuit voltage measurement and the net change in charge.

10. The system of claim 9, wherein the controller is further configured to:

repeat a process of estimating the capacity of the battery at multiple times to generate multiple estimates for the capacity of the battery; and

use the multiple estimates to produce a more-accurate estimate for the capacity of the battery.

11. The system of claim 10, wherein while using the multiple estimates to produce a more-accurate estimate for the capacity of the battery, the controller is configured to:

use the multiple estimates to determine a capacity-change trend for the battery; and

apply the capacity-change trend to a reference measurement for the capacity of the battery obtained while the portable electronic device was not plugged in to a power adapter to produce the more-accurate estimate for the capacity of the battery.

12. The system of claim 11, wherein while determining the capacity-change trend, the controller is configured to fit the multiple estimates generated at multiple times to a linear function.

13. The system of claim 11, wherein while determining the capacity-change trend, the controller is configured to fit the multiple estimates generated at multiple times to a second-order function.

14. The system of claim 9,

wherein the first state of charge is higher than the second state of charge;

and

wherein causing the battery to transition from the first state of charge to the second state of charge involves powering the portable electronic device from the battery and not the power adapter while the portable electronic device is drawing current.

15. The system of claim 14,

wherein the first state of charge is a fully charged state for the battery;

and

wherein the second state of charge is within 5% of the fully charged state of the battery.

16. The system of claim 9,

wherein the second state of charge is higher than the first state of charge;

and

wherein causing the battery to transition from the first state of charge to the second state of charge involves charging the battery using current supplied by the power adapter.

17. A system for tracking a capacity of a battery in a portable electronic device, comprising:

a controller for the portable electronic device configured to estimate the capacity of the battery by,

performing a first open-circuit voltage measurement on the battery while the battery rests at a first state of charge,

causing the battery to transition to a second state of charge while the portable electronic device remains plugged in to the power adapter,

while the battery is transitioning to the second state of charge, monitoring a current through the battery to determine a net change in charge for the battery,

performing a second open-circuit voltage measurement on the battery while the battery rests at the second state of charge, and

calculating the estimate for the capacity of the battery based on the first open-circuit voltage measurement, the second open-circuit voltage measurement and the net change in charge.

18. The system of claim 17, wherein the controller is further configured to:

repeat a process of estimating the capacity of the battery at multiple times to generate multiple estimates for the capacity of the battery; and

use the multiple estimates to produce a more-accurate estimate for the capacity of the battery.

19. The system of claim 18, wherein while using the multiple estimates to produce a more-accurate estimate for the capacity of the battery, the controller is configured to:

use the multiple estimates to determine a capacity-change trend for the battery; and

apply the capacity-change trend to a reference measurement for the capacity of the battery obtained while the portable electronic device was not plugged in to a power adapter to produce the more-accurate estimate for the capacity of the battery.

20. The system of claim 17,

wherein the first state of charge is higher than the second state of charge;

and

wherein causing the battery to transition from the first state of charge to the second state of charge involves powering the portable electronic device from the battery and not the power adapter while the portable electronic device is drawing current.

21. The system of claim 17,

wherein the second state of charge is higher than the first state of charge;

and

wherein causing the battery to transition from the first state of charge to the second state of charge involves charging the battery using current supplied by the power adapter.