Method and apparatus for determining a thermal state of a battery taking into account battery aging

Patent metadata

Field	Value
Publication number	US-9500538-B2
Application number	US-201313959769-A
Country	US
Kind code	B2
Filing date	Aug 6, 2013
Priority date	Mar 14, 2013
Publication date	Nov 22, 2016
Grant date	Nov 22, 2016

Abstract

An electronic system, or its battery thermal management system, determines a thermal state of a battery used in the electronic system. A temperature at a position proximate the battery's cell is sensed during operation of the electronic system to produce a sensed value. Additionally, a temperature offset value is determined based on an aging factor for the battery. The sensed value is then adjusted based on the offset value to produce an adjusted value representative of the thermal state of the battery. According to one embodiment, a relationship between temperature offset value and battery aging factor is prestored in a memory of the electronic system. In such a case, the offset value may be retrieved from memory periodically or in response to a trigger event based on a determined aging factor. According to another embodiment, the offset value may be computed in real time based on a determined aging factor.

First claim

What is claimed is:

1. A method for determining a thermal state of a battery used in an electronic system, the battery including one or more cells, the method comprising:
sensing, within the electronic system, temperature at a position outside the one or more cells of the battery during operation of the electronic system to produce a sensed temperature value, wherein the sensed temperature value is related to a temperature within the one or more cells by way of a temperature offset value that varies with an age of the battery;
determining an aging factor indicative of the age of the battery;
determining the temperature offset value based on the aging factor for the battery; and
adjusting the sensed temperature value based on the temperature offset value to produce an adjusted temperature value representative of the temperature within the one or more cells.

2. The method of claim 1 , wherein determining the temperature offset value based on the aging factor for the battery comprises:
retrieving the temperature offset value from a memory of the electronic system based on the aging factor, wherein a relationship between temperature offset value and aging factor for the battery was prestored in the memory.

3. The method of claim 1 , wherein the aging factor for the battery comprises a quantity of charge-discharge cycles for the battery.

4. The method of claim 3 , further comprising:
detecting a cumulative capacity of the battery during operation of the electronic system; and
determining the quantity of charge-discharge cycles based on the cumulative capacity.

5. The method of claim 4 , wherein determining the temperature offset value based on an aging factor for the battery comprises:
retrieving the temperature offset value from a memory of the electronic system based on the quantity of charge-discharge cycles, wherein a relationship between temperature offset value and quantity of charge-discharge cycles for the battery was prestored in the memory.

6. The method of claim 4 , wherein determining the quantity of charge-discharge cycles based on the cumulative capacity comprises:
determining a ratio of the cumulative capacity to a full capacity for the battery to produce the quantity of charge-discharge cycles.

7. The method of claim 4 , wherein determining the quantity of charge-discharge cycles based on the cumulative capacity comprises:
determining a ratio of the cumulative capacity to a full capacity for the battery;
multiplying the ratio by a cycle life fade factor for the battery to produce an adjusted ratio; and
summing the ratio and the adjusted ratio to produce the quantity of charge-discharge cycles.

8. The method of claim 4 , wherein determining the quantity of charge-discharge cycles based on the cumulative capacity comprises:
determining a ratio of the cumulative capacity to a full capacity for the battery;
multiplying the ratio by a cycle life fade factor for the battery to produce an adjusted ratio;
determining a quantity of partial charge cycles for the battery;
multiplying the quantity of partial charge cycles by a partial charge factor to produce an adjusted quantity of partial charge cycles;
summing the ratio and the adjusted ratio to produce a summation; and
subtracting the adjusted quantity of partial charge cycles from the summation to produce the quantity of charge-discharge cycles.

9. The method of claim 8 , wherein determining the quantity of partial charge cycles for the battery comprises:
determining occurrences of a plurality of charging events for the battery;
determining a state of charge for the battery at an end of each charging event;
determining that a particular charging event is a partial charge cycle when the state of charge for the battery at the end of the particular charging event is less than a predetermined percentage of a full state of charge for the battery; and
determining the quantity of partial charge cycles based on a quantity of charging events that qualify as partial charge cycles.

10. The method of claim 9 , wherein determining the state of charge for the battery at the end of each charging event comprises:
determining an open circuit output voltage of the battery at the end of each charging event; and
determining the state of charge for the battery based on the open circuit voltage.

11. The method of claim 1 , wherein the aging factor comprises a heat generation factor for the battery.

12. The method of claim 11 , further comprising:
measuring an impedance of the battery during operation of the electronic system to produce an aged battery impedance;
determining a quantity of heat generated by the battery during operation of the electronic system based on the aged battery impedance to produce an aged heat generation value; and
determining the heat generation factor based on the aged heat generation value.

13. The method of claim 12 , wherein determining the heat generation factor based on the aged heat generation value comprises:
retrieving an initial heat generation value from a memory of the electronic system, the initial heat generation value representing an amount of heat generated by the battery prior to aging of the battery;
subtracting the initial heat generation value from the aged heat generation value to produce a heat generation value difference; and
dividing the heat generation value difference by the aged heat generation value to produce the heat generation factor.

14. The method of claim 12 , wherein determining the temperature offset value based on the aging factor for the battery comprises:
retrieving an initial temperature offset value from a memory of the electronic system, the initial temperature offset value representing a temperature offset value applied to the sensed temperature value prior to aging of the battery;
multiplying the initial temperature offset value by the heat generation factor to produce a scaled initial temperature offset value; and
summing the scaled initial temperature offset value and the initial temperature offset value to produce the temperature offset value.

15. The method of claim 12 , wherein measuring the impedance of the battery during operation of the electronic system comprises:
measuring the impedance of the battery periodically.

16. The method of claim 12 , wherein measuring the impedance of the battery during operation of the electronic system comprises:
measuring the impedance of the battery upon occurrence of a triggering event.

17. The method of claim 11 , wherein determining the temperature offset value based on the aging factor for the battery comprises:
retrieving an initial temperature offset value from a memory of the electronic system, the initial temperature offset value representing a given temperature offset value applied to the sensed temperature value prior to aging of the battery;
multiplying the initial temperature offset value by the heat generation factor to produce a scaled initial temperature offset value; and
summing the scaled initial temperature offset value and the initial temperature offset value to produce the temperature offset value.

18. The method of claim 1 , wherein the aging factor comprises an aged heat generation value for the battery.

19. The method of claim 18 , wherein determining the temperature offset value based on the aging factor for the battery comprises:
measuring an impedance of the battery during operation of the electronic system to produce an aged battery impedance;
determining a quantity of heat generated by the battery during

Assignees

• Motorola Mobility Llc
• Google Inc

Inventors

• Maleki Hossein
• Howard Jason N

Classifications

• H01M10/486 Primary

  for measuring temperature · CPC title

• G01K13/00 Primary

  Thermometers specially adapted for specific purposes · CPC title

• G01K15/005

  Calibration · CPC title

• G01R31/3606

  Physics · mapped topic

• G01R31/3675

  Physics · mapped topic