Battery thermal system control strategy

• US 8,410,760 B2
• Filed: 08/02/2010
• Issued: 04/02/2013
• Est. Priority Date: 08/02/2010
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Formanski, Volker, Reischmann, Marc
• Primary Examiner(s): Fantu, Yalkew
• Application Number:
  US12/848,726
• Publication Number:
  US 20120029724A1
• Time in Patent Office: 974 Days
• Field of Search: 320/150
• US Class Current: 320/150
• CPC Class Codes: H01M 10/443 in response to temperature
• CPC Class Codes: H01M 10/613 Cooling or keeping cold
• CPC Class Codes: H01M 10/615 Heating or keeping warm
• CPC Class Codes: H01M 10/633 characterised by algorithms, flow charts, software details or the like
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A method and system for controlling temperature in an electric vehicle battery pack which preserves battery pack performance and longevity while maximizing vehicle driving range. A controller prescribes a minimum allowable operating temperature in the battery pack, where the minimum operating temperature increases as battery pack state of charge and remaining useful life decrease. During vehicle driving operations, the minimum allowable temperature is computed, and a thermal management system is used to warm the battery pack only if necessary to raise its temperature above the calculated minimum level. By minimizing use of the thermal management system to warm the battery pack, energy consumption is reduced and vehicle driving range is increased, while not adversely affecting battery pack performance or durability. The same strategy is employed during charging, which reduces the amount of energy consumed from the grid for warming the battery pack.

Claims

1. A method for thermal management of a battery pack, said method comprising:

determining state of charge of the battery pack and designating the state of charge most recently determined as current state of charge;

determining remaining useful life of the battery pack;

defining a minimum set point temperature for operation of the battery pack, where the minimum set point temperature is based on required battery pack performance, the state of charge of the battery pack, and the remaining useful life of the battery pack;

measuring temperature in the battery pack; and

controlling the temperature in the battery pack to prevent the battery pack from being operated when the temperature is below the minimum set point temperature.

2. The method of claim 1 wherein defining a minimum set point temperature for operation of the battery pack includes increasing the minimum set point temperature as the state of charge of the battery pack decreases.

3. The method of claim 1 wherein defining a minimum set point temperature for operation of the battery pack includes increasing the minimum set point temperature as the remaining useful life of the battery pack decreases.

4. The method of claim 1 wherein controlling the temperature in the battery pack includes adding heat to the battery pack until the temperature in the battery pack is raised to the minimum set point temperature at the current state of charge and remaining useful life.

5. The method of claim 1 wherein controlling the temperature in the battery pack includes controlling the flow of a fluid through the battery pack to add heat to the battery pack.

6. The method of claim 1 wherein the battery pack is used in an electric vehicle.

7. The method of claim 1 wherein the battery pack is a lithium-ion battery pack.

8. A method for thermal management of a lithium-ion battery pack in an electric vehicle, said method comprising:

determining state of charge of the battery pack and designating the state of charge most recently determined as current state of charge;

determining remaining useful life of the battery pack;

defining a first minimum set point temperature for operation of the battery pack, where the first minimum set point temperature is based on required battery pack performance, the state of charge of the battery pack, and the remaining useful life of the battery pack;

defining a second minimum set point temperature for operation of the battery pack, where the second minimum set point temperature is based on required battery pack durability, the state of charge of the battery pack, and the remaining useful life of the battery pack;

defining a maximum set point temperature for operation of the battery pack;

measuring temperature in the battery pack; and

controlling the temperature in the battery pack based on the first minimum set point temperature, the second minimum set point temperature, and the maximum set point temperature.

9. The method of claim 8 wherein defining a first minimum set point temperature for operation of the battery pack includes increasing the first minimum set point temperature as the state of charge of the battery pack decreases.

10. The method of claim 8 wherein defining a first minimum set point temperature for operation of the battery pack includes increasing the first minimum set point temperature as the remaining useful life of the battery pack decreases.

11. The method of claim 8 wherein controlling the temperature in the battery pack includes selecting either the first minimum set point temperature or the second minimum set point temperature, and adding heat to the battery pack until the temperature in the battery pack is raised to the selected set point temperature at the current state of charge and remaining useful life.

12. The method of claim 8 wherein controlling the temperature in the battery pack includes removing heat from the battery pack until the temperature in the battery pack is lowered to the maximum set point temperature.

13. The method of claim 8 wherein controlling the temperature in the battery pack includes controlling the flow of a fluid through the battery pack to add heat to or remove heat from the battery pack.

14. A thermal management system for a battery pack providing electrical energy to an apparatus, said thermal management system comprising:

a plurality of sensors for measuring voltage in the battery pack and temperature in the battery pack, where the measured voltage is used to determine state of charge of the battery pack, and the state of charge last determined is designated as current state of charge;

means for determining remaining useful life of the battery pack;

a heating and cooling system for adding heat to or removing heat from the battery pack; and

a controller for managing the temperature in the battery pack, said controller being responsive to measurement signals from the sensors and being configured to control the heating and cooling system to control the temperature in the battery pack as a function of the state of charge of the battery pack and the remaining useful life of the battery pack.

15. The thermal management system of claim 14 wherein the controller is configured to control the temperature in the battery pack by defining a first minimum set point temperature, and commanding the heating and cooling system to add heat to the battery pack until the temperature in the battery pack is raised to the first minimum set point temperature at the current state of charge and the remaining useful life.

16. The thermal management system of claim 15 wherein the controller increases the first minimum set point temperature as the state of charge of the battery pack decreases, and increases the first minimum set point temperature as the remaining useful life of the battery pack decreases.

17. The thermal management system of claim 15 wherein the controller also defines a second minimum set point temperature, where the first minimum set point temperature is based on performance considerations and the second minimum set point temperature is based on durability considerations of the battery pack, and wherein the controller includes rules to select either the first minimum set point temperature or the second minimum set point temperature.

18. The thermal management system of claim 14 wherein the controller is configured to control the temperature in the battery pack by defining a maximum set point temperature, and commanding the heating and cooling system to remove heat from the battery pack until the temperature in the battery pack is lowered to the maximum set point temperature.

19. The thermal management system of claim 14 wherein the battery pack is a lithium-ion battery pack and the apparatus is an electric vehicle.