Patent Application

App. No. 11/459,380

Abstract

Claims (39)

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.

Assignments (10)