Direct current power management system

1. A power system comprising:

a power source configured to output a first voltage;

a plurality of batteries, each battery configured to provide a second voltage;

a plurality of switches coupled between each of said batteries; and

a controller coupled to said plurality of switches and configured to

place said plurality of switches in a first mode of operation so that said plurality of batteries is coupled in parallel and receives a charge from said power source, and

place said plurality of switches in a second mode of operation so that said plurality of batteries is coupled in series and provides a combined voltage greater than the first voltage and the second voltage.

2. The power system of claim 1 wherein said controller has a first input coupled to an output of said power source; and wherein said controller is configured to place said plurality of switches in the first mode of operation only when the first voltage is greater than or equal to a threshold voltage.

3. The power system of claim 2 wherein said controller has a second input coupled to an output of said plurality of batteries; and wherein said controller is configured to place said plurality of switches in the first mode of operation only when the second voltage is less than the threshold voltage.

4. The power system of claim 1 further comprising a power switch coupled between the power source and each battery of said plurality thereof.

5. The power system of claim 4 wherein said controller is configured to control said power switch.

6. The power system of claim 4 wherein said controller is configured to close said power switch after said plurality of switches has entered the first mode of operation.

7. The power system of claim 4 wherein said controller is configured to open said power switch in the second mode of operation.

8. The power system of claim 1 wherein said power source comprises a starter battery, and an alternator coupled thereto.

9. A vehicle comprising:

an internal combustion engine;

a load; and

a vehicle power system comprising

a vehicle power source configured to output a first voltage and comprising a vehicle starter battery, and an alternator coupled thereto, said alternator being driven by said internal combustion engine,

a plurality of batteries, each battery configured to provide a second voltage,

a plurality of switches coupled between each of said batteries, and

a controller coupled to said plurality of switches and configured to

place said plurality of switches in a first mode of operation so that said plurality of batteries is coupled in parallel and receives a charge from said vehicle power source, and

place said plurality of switches in a second mode of operation so that said plurality of batteries is coupled in series and provides a combined voltage greater than the first voltage and the second voltage, the combined voltage driving said load.

10. The vehicle of claim 9 wherein said controller has a first input coupled to an output of said vehicle power source; and wherein said controller is configured to place said plurality of switches in the first mode of operation only when the first voltage is greater than or equal to a threshold voltage.

11. The vehicle of claim 10 wherein said controller has a second input coupled to an output of said plurality of batteries; and wherein said controller is configured to place said plurality of switches in the first mode of operation only when the second voltage is less than the threshold voltage.

12. The vehicle of claim 9 wherein said controller has a third input coupled to the load; and wherein said controller is configured to place said plurality of switches in the first and second modes of operation based upon an operational characteristic of the load.

13. The vehicle of claim 9 wherein said vehicle power system further comprises a power switch coupled between the vehicle power source and each battery of said plurality thereof.

14. The vehicle of claim 13 wherein said load comprises at least one of an air conditioning load, a vacuum load, a pump load, and an air compressor load.

15. A method of operating a power system comprising:

operating a controller coupled to a plurality of switches, the plurality of switches being coupled between each of a plurality of batteries; and

operating the controller to

place the plurality of switches in a first mode of operation so that the plurality of batteries is coupled in parallel and receives a charge from a power source, and

place the plurality of switches in a second mode of operation so that the plurality of batteries is coupled in series and provides a combined voltage greater than a first voltage from a power source and a second voltage from each battery.

16. The method of claim 15 wherein the controller has a first input coupled to an output of the power source; and further comprising operating the controller to place the plurality of switches in the first mode of operation only when the first voltage is greater than or equal to a threshold voltage.

17. The method of claim 16 wherein the controller has a second input coupled to an output of the plurality of batteries; and further comprising operating the controller to place the plurality of switches in the first mode of operation only when the second voltage is less than the threshold voltage.

18. The method of claim 15 further comprising operating a power switch coupled between the power source and each battery of the plurality thereof.

19. The method of claim 18 further comprising operating the controller to control the power switch.