METHOD AND APPARATUS FOR IMPROVING CYCLE LIFE CAPACITY OF A BATTERY PACK

• US 20140077769A1
• Filed: 09/18/2012
• Published: 03/20/2014
• Est. Priority Date: 09/18/2012
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola Mobility LLC (Lenovo Group Ltd.)
• Inventors: Maleki, Hossein, Hallmark, Jerald A.
• Granted Patent: US 9,787,106 B2
• Time in Patent Office: Days
• US Class Current: 320/136
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
• CPC Class Codes: H02J 7/0014 Circuits for equalisation of charge between batteries
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]
• CPC Class Codes: H02J 7/00714 in response to battery charging or discharging current

Abstract

A method (900) of reducing variation of an energy storage capacity of a battery across its cycle life is disclosed. The method can include the step (901) of monitoring one or more voltages of one or more cells of a battery for a predetermined discharge usage time. Where a profile of the one or more voltages during the predetermined discharge usage time meets a predefined usage criterion, the method can include the step (907) of increasing a discharge voltage limit of the one or more cells. An energy management circuit (614) can be configured with a control circuit (702) operable to increase the discharge limit and to limit discharge of the cells when the discharge limit is reached.

Claims

1. A method of reducing variation of an energy storage or usage capacity of a battery across its cycle life, comprising:

monitoring, with a voltage sensor, one or more voltages of one or more cells of the battery for a predetermined discharge usage time; and

where a profile of the one or more voltages during the predetermined discharge usage time meets a predefined usage criterion, increasing a discharge voltage limit of the one or more cells.

2. The method of claim 1, wherein the predefined usage criterion comprises the one or more voltages remaining above a rated discharge voltage for the one or more cells by a predetermined margin.

3. The method of claim 2, wherein the predetermined margin is about twenty-five percent.

4. The method of claim 1, further comprising providing, on a user interface of a portable electronic device operable with the battery, a low battery indication when the one or more voltages fall to the discharge voltage limit.

5. The method of claim 1, further comprising limiting a discharge current from the one or more cells when the one or more voltages fall to the discharge voltage limit.

6. The method of claim 5, wherein the limiting comprises increasing a series impedance of a discharge control device coupled serially between the battery and a load.

7. The method of claim 1, wherein the increasing comprises increasing the discharge voltage limit by at least 400 mV.

8. The method of claim 1, wherein the increasing comprises increasing comprises changing the discharge voltage limit from about 2.7 volts to at least 3.1 volts.

9. The method of claim 1, wherein the predetermined discharge usage time comprises five or more charging cycles.

10. The method of claim 1, further comprising:

determining an unused capacity of the one or more cells from the profile; and

determining a characteristic cell voltage corresponding to the unused capacity;

wherein the increasing comprises increasing the discharge voltage limit as a function of the characteristic cell voltage.

11. The method of claim 10, wherein the increasing comprises increasing the discharge voltage limit to a level above a rated discharge voltage and below the characteristic cell voltage.

12. An energy management circuit for coupling to one or more rechargeable cells, the energy management circuit comprising:

a control circuit, operable with;

a voltage sense node configured to sense a voltage across the one or more rechargeable cells; and

a discharge control node configured to control a discharge current limiter coupled serially with the one or more cells;

wherein the control circuit is configured to, upon detecting a profile of the voltage during a predetermined usage time meeting a predefined criterion, increase a discharge voltage limit for the one or more rechargeable cells.

13. The energy management circuit of claim 12, wherein the control circuit is further configured to apply a control signal configured to increase a serial impedance of the discharge current limiter upon the voltage at the voltage sense node falling to the discharge voltage limit.

14. The energy management circuit of claim 12, wherein anodes of the one or more cells comprise silicon and a silicon alloying carbon.

15. The energy management circuit of claim 12, wherein both the one or more cells and the control circuit are both disposed within a battery pack.

16. The energy management circuit of claim 12, wherein:

the control circuit is configured to deliver a prompt to an electronic device, coupled to the control circuit, requesting user permission to increase the discharge voltage limit;

receive a user response from the electronic device in response to the prompt; and

increase the discharge voltage limit only where the user response comprise an authorization to increase the discharge voltage limit.

17. The energy management circuit of claim 16, wherein the prompt comprises indicia of an estimated capacity compromise that will result when the discharge voltage limit is increased.

18. A method of reducing variation in energy storage capacity of a battery across a cycle life, comprising:

monitoring, with a control circuit coupled to one or more cells of the battery, a user discharge profile; and

where the user discharge profile meets a predefined criterion, prompting, with a user interface operable with the control circuit, for authorization to decrease a discharge energy capacity limit of the battery.

19. The method of claim 18, further comprising:

receiving an electronic signal representing the authorization; and

decreasing the discharge energy capacity limit of the battery by increasing a discharge voltage limit of the one or more cells.

20. The method of claim 18, wherein the predefined criterion comprises fully discharging the one or more cells at least once within a predetermined discharge usage time.