Input voltage based system and method for charging a vehicle battery

1. An automotive vehicle power system comprising:

a battery charger having an input and output and configured to (i) receive electrical energy via the input when the input is electrically connected with an electrical energy source and (ii) reduce a current provided at the output from a commanded value to a target value that varies according to a voltage at the input if the voltage at the input falls within a predetermined range of voltages.

2. The system of claim 1 wherein the battery charger further has a second output and is further configured to reduce a voltage set point of the second output from a commanded value to a target value if the voltage at the input falls within the predetermined range of voltages.

3. The system of claim 2 further comprising an auxiliary battery electrically connected with the battery charger via the second output.

4. The system of claim 1 further comprising a traction battery electrically connected with the battery charger via the output.

5. The system of claim 1 wherein the battery charger is further configured to reduce the current provided at the output from the commanded value or target value to zero if the voltage at the input falls below the predetermined range of voltages.

6. The system of claim 5 wherein the battery charger is further configured to increase the current provided at the output from zero to the target value if the voltage at the input subsequently falls within the predetermined range of voltages.

7. The system of claim 5 wherein the battery charger is further configured to increase the current provided at the output from zero to the commanded value if the voltage at the input subsequently exceeds the predetermined range of voltages.

8. A plug-in hybrid electric vehicle comprising:

an electric machine;

a traction battery electrically connected with the electric machine; and

a battery charger configured to receive electrical energy from an electrical energy source if electrically connected with the electrical energy source and to provide a current to the traction battery at a target value that varies according to a voltage associated with the electrical energy if the voltage associated with the electrical energy falls within a predetermined range of voltages.

9. The vehicle of claim 8 further comprising an auxiliary battery, wherein the battery charger is further configured to reduce a voltage set point of the auxiliary battery from a commanded value to a target value if the voltage associated with the electrical energy falls within the predetermined range of voltages.

10. The vehicle of claim 8 wherein the battery charger is further configured to reduce the current provided to the traction battery to zero if the voltage associated with the electrical energy falls below the predetermined range of voltages.

11. The vehicle of claim 10 wherein the battery charger is further configured to increase the current provided to the traction battery from zero to the target value if the voltage associated with the electrical energy subsequently falls within the predetermined range of voltages.

12. The vehicle of claim 10 wherein the battery charger is further configured to increase the current provided to the traction battery from zero to a commanded value if the voltage associated with the electrical energy subsequently exceeds the predetermined range of voltages.

13. A method of charging a vehicle battery comprising:

determining a voltage on an AC power line electrically connected with an electrical energy source;

determining whether the voltage falls within a predetermined range of voltages; and

outputting a current to a vehicle traction battery at a target value that varies according to the voltage if the voltage falls within the predetermined range of voltages.

14. The method of claim 13 further comprising outputting the current to the vehicle traction battery at a commanded value if the voltage exceeds the predetermined range of voltages.

15. The method of claim 14 further comprising reducing the current output to zero if the voltage falls below the predetermined range of voltages.

16. The method of claim 15 further comprising increasing the current output to the target value if the voltage subsequently falls within the predetermined range of voltages.

17. The method of claim 15 further comprising increasing the current output to the commanded value if the voltage subsequently exceeds the predetermined range of voltages.

18. The method of claim 13 further comprising reducing a voltage set point output to a vehicle auxiliary battery from a commanded value to a target value if the voltage falls within the predetermined range of voltages.