METHOD FOR IMPROVING FUEL ECONOMY OF A HYBRID VEHICLE

• US 20080042615A1
• Filed: 07/24/2006
• Published: 02/21/2008
• Est. Priority Date: 07/24/2006
• Status: Abandoned Application

• Current Assignee: GM Global Technology Operations Incorporated (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (General Motors Company)
• Inventors: Serrels, Richard K., Serrels, Gretchen, Omell, William J., Breese, Richard M.
• Application Number:
  US11/459,380
• Publication Number:
  US 20080042615A1
• Time in Patent Office: Days
• US Class Current: 320/101
• CPC Class Codes: B60L 1/003 to auxiliary motors, e.g. for pumps, compressors
• CPC Class Codes: B60L 1/02 to electric heating circuits
• CPC Class Codes: B60L 2210/10 DC to DC converters
• CPC Class Codes: B60L 50/15 with additional electric power supply with capacitors charged by engine-driven generators B60L50/40; with batteries charged by engine-driven generators B60L50/61
• CPC Class Codes: H02J 7/00306 Overdischarge protection
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]
• CPC Class Codes: H02J 7/1438 in combination with power supplies for loads other than batteries
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility

Abstract

A fuel economy control method for a hybrid vehicle includes estimating a temperature of a battery, measuring a current of the battery, and measuring a voltage of the battery. A nominal optimum charging voltage is determined as a function of a state of charge (SOC) of the battery and the estimated temperature. The nominal optimum charging voltage is reduced to a fuel economy minimum charging voltage if the SOC is above a predetermined level and the current is within a predetermined range. The battery is then charged at the fuel economy minimum charging voltage using a DC/DC converter.

Claims

1. A fuel economy control method for a hybrid vehicle comprising:

determining a state of charge (SOC) of a battery;

determining a nominal optimum charging voltage of said battery;

reducing said nominal optimum charging voltage to a fuel economy minimum charging voltage if said SOC is above a predetermined level and said current is within a predetermined range; and

charging said battery at said fuel economy minimum using a DC/DC converter.

2. The method of claim 1 wherein said predetermined level is approximately 80%.

3. The method of claim 1 wherein said predetermined range is between −

8 A and 15 A.

4. The method of claim 1 wherein said step of reducing is performed if an outside air temperature is within a first temperature range, a vehicle speed is less than a predetermined speed, and an accessory is off.

5. The method of claim 1 wherein said nominal optimum charging voltage is based on said SOC.

6. The method of claim 1 further comprising:

estimating a temperature of said battery; and

measuring a voltage of said battery, wherein said SOC is based upon said temperature, said voltage, and said current.

7. The method of claim 1 wherein determining said nominal optimum charging voltage includes:

determining a running SOC of said battery; and

interpolating a value of said nominal optimum charging voltage based on said running SOC and said temperature.

8. The method of claim 7 wherein interpolating is based upon a plurality of calibration constants.

9. A fuel economy control method for a hybrid vehicle comprising:

estimating a temperature of a battery;

measuring current supplied by said battery;

determining a state of charge (SOC) of said battery;

determining a nominal optimum charging voltage of said battery;

reducing said nominal optimum charging voltage to a fuel economy minimum charging voltage if said SOC is above a predetermined level and said current is within a predetermined range; and

charging said battery at said fuel economy minimum using a DC/DC converter.

10. The method of claim 9 wherein said predetermined level is 80%.

11. The method of claim 9 wherein said predetermined range is between −

8 A and 15 A.

12. The method of claim 9 wherein said reducing step is performed if an outside air temperature is within a first temperature range, a vehicle speed is less than a predetermined speed, and an accessory is off.

13. The method of claim 9 wherein said nominal optimum charging voltage is based on said SOC.

14. The method of claim 9 wherein determining said nominal optimum charging voltage includes:

determining a running SOC of said battery; and

interpolating a value of said nominal optimum charging voltage based on said running SOC and said temperature.

15. A method of protecting a battery from sulfation, comprising:

determining a nominal optimum charging voltage as a function of a state of charge (SOC) of a battery;

comparing said nominal optimum charging voltage to a threshold value; and

increasing said nominal optimum charging voltage to above said threshold value and charging said battery at said increased nominal optimum charging voltage with a DC/DC converter if said nominal optimum charging voltage is below said threshold value for a first predetermined period of time.

16. The method of claim 15 further comprising estimating a temperature of the battery.

17. The method of claim 16 wherein said nominal optimum charging voltage is based on said battery temperature estimate.

18. The method of claim 15 wherein said threshold value is 13.2V.

19. The method of claim 15 wherein said first predetermined period is 30 minutes.

20. The method of claim 15 further comprising holding said nominal optimum charging voltage above said threshold level for at least a second predetermined period of time.