Charging method for extending battery life in the presence of high temperature

• US 6,894,459 B2
• Filed: 07/29/2003
• Issued: 05/17/2005
• Est. Priority Date: 07/29/2003
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Maleki, Hossein, Howard, Jason N.
• Primary Examiner(s): Sherry, Michael
• Assistant Examiner(s): Grant, Robert
• Application Number:
  US10/628,610
• Publication Number:
  US 20050024022A1
• Time in Patent Office: 658 Days
• Field of Search: 320/150, 320/151, 320/152, 320/132
• US Class Current: 320/150
• CPC Class Codes: H02J 7/0069 Charging or discharging for charge maintenance, battery initiation or rejuvenation
• CPC Class Codes: H02J 7/007194 of the battery

Abstract

A method of charging a battery is provided that alters the amount of energy stored within the battery based upon a temperature profile across time. Battery materials and components, like liquid electrolyte or electrodes for instance, can be damaged when a rechargeable cell is exposed to elevated temperatures for extended amounts of time, thereby reducing the overall amount of energy that may be stored within the cell. This method monitors stored energy capacity and temperature. When a fully-charged cell is held at a temperature that exceeds a predetermined temperature threshold for an extended amount of time, the method discharges the cell, thereby reducing the amount of energy stored within the cell. For example, when a single, lithium-ion cell is maintained at 4.2 V for over 10 hours, the method will discharge the cell by roughly 1% or 50 mV. The discharge may be either automatic, or at the prompt of a user.

Claims

1. A method of charging a battery, the method comprising the steps of:

a. monitoring a temperature of at least one rechargeable cell disposed within the battery;

b. monitoring an amount of energy stored within the at least one rechargeable cell;

c. monitoring time when both the temperature exceeds a predetermined temperature threshold and the amount of energy stored exceeds a predetermined capacity threshold; and

d. reducing the amount of energy stored within the at least one rechargeable cell when both the temperature exceeds the predetermined temperature threshold and the amount of energy stored exceeds the predetermined capacity threshold for at least a continuous, predetermined amount of time.

5. The method of claim 1, wherein the predetermined temperature threshold is at least 55 degrees centigrade.

6. The method of claim 1, wherein the reducing the amount of energy comprises a reduction of at least 1 per cent of a maximum energy capacity of the at least one rechargeable cell.

7. The method of claim 1, further comprising the step of prompting a user prior to the reducing the amount of energy.

8. The method of claim 7, further comprising the step of waiting at least a predetermined wait time as directed by a user prior to the reducing the amount of energy.

9. The method of claim 1, wherein the predetermined amount of time is at least 10 hours.

2. The method of step 1, wherein the monitoring the amount of energy is accomplished by a method selected from the group consisting of measuring a voltage across the at least one rechargeable cell and reading a fuel gauge.

3. The method of step 2, wherein the monitoring the amount of energy is accomplished by measuring a voltage across the at least one rechargeable cell, further wherein the predetermined capacity threshold comprises a voltage of at least 4.1 V across the at least one rechargeable cell.

4. The method of claim 3, wherein the reducing the amount of energy comprises discharging the at least one rechargeable cell until the voltage across the cell is at least 50 mV below the predetermined capacity threshold.

10. A method of charging a rechargeable, electrochemical cell, the method comprising the steps of:

a. providing a battery pack comprising at least one electrochemical cell;

b. providing a processor capable of measuring a temperature and a voltage of the at least one electrochemical cell, the processor further being able of measuring a duration of time;

c. monitoring the temperature of at least one electrochemical cell;

d. monitoring the voltage of the at least one electrochemical cell;

e. monitoring time when both the temperature exceeds a predetermined temperature threshold and the voltage exceeds a predetermined voltage threshold; and

f. reducing an amount of energy stored within the at least one electrochemical cell by at least one percent when both the temperature exceeds the predetermined temperature threshold and the voltage exceeds the predetermined voltage threshold for at least a continuous, predetermined amount of time.

13. The method of claim 10, wherein the predetermined temperature threshold is at least 55°

centigrade.

14. The method of claim 10, further comprising the step of prompting a user prior to reducing the amount of energy.

15. The method of claim 14, further comprising the step of waiting at least a predetermined wait time as directed by a user prior to reducing the amount of energy.

16. The method of claim 10, wherein the predetermined amount of time is at least 10 hours.

11. The method of step 10, wherein the predetermined voltage threshold comprises a voltage of at least 4.1V across the at least one electrochemical cell.

12. The method of claim 11, wherein the reducing the amount of energy comprises discharging the at least one electrochemical cell until the voltage across the cell Is at least 50 mV below the predetermined voltage threshold.