Method of externally charging a powertrain

1. A method of externally charging a powertrain comprising:

monitoring a voltage level of a first battery;

comparing the monitored voltage level to first and second voltage thresholds, the first voltage threshold having a higher voltage than the second voltage threshold, wherein the first voltage threshold comprises an overall voltage of the first battery at which the engine may not start due to low overall battery voltage and the second voltage threshold comprises a voltage of the first battery at which it is undesirable to initiate an engine start procedure;

when the monitored voltage is at least the second voltage threshold,

initiating an engine starting procedure, and

terminating the engine start procedure when both the monitored voltage level is below the first voltage threshold and an engine does not start during the engine starting procedure; and

when the monitored voltage level is below the second voltage threshold, charging the first battery by supplying power from an external power source and increasing voltage of the power supplied by the external power source within the powertrain.

2. The method of claim 1 , wherein monitoring the voltage level of the first battery comprises monitoring an overall voltage level of the first battery and wherein the method further comprises sending an output signal when the overall voltage level of the first battery is below a first overall voltage threshold.

3. The method of claim 1 , wherein monitoring the voltage level of the first battery comprises monitoring a cell module voltage of the first battery and wherein the method further comprises sending an output signal when the cell module voltage is below a first cell module voltage threshold.

4. The method of claim 1 , wherein monitoring the voltage level of the first battery includes both monitoring an overall voltage level of the first battery and a cell module voltage of the first battery, and wherein the method further comprises sending an output signal when at least one of the overall voltage level is below a first overall voltage threshold and the cell module voltage is below a first cell module voltage threshold.

5. The method of claim 1 further comprising:

monitoring a power level of the first battery;

determining when the power level is below a first power threshold; and

when the power level is below the first power threshold, sending an output signal.

6. The method of claim 5 further comprising utilizing a temperature level measurement and the monitored voltage level to monitor the power level of the first battery.

7. The method of claim 5 further comprising:

determining a state of charge of the first battery based on the monitored voltage level; and

determining the power level of the first battery based on the state of charge of the first battery.

8. A method of externally charging a powertrain comprising:

monitoring a voltage level of a first battery;

comparing the monitored voltage level to first and second voltage thresholds, the first voltage threshold having a higher voltage than the second voltage threshold;

when the monitored voltage is at least the second voltage threshold,

performing an engine starting procedure, and

terminating the engine start procedure when both the monitored voltage level is below the first voltage threshold and an engine does not start during the engine starting procedure, wherein the engine starting procedure is performed for a selected time period and the output signal is sent when the engine does not start within the selected time period; and

when the monitored voltage level is below the second voltage threshold, charging the first battery by supplying power from an external power source and increasing voltage of the power supplied by the external power source within the powertrain.

9. The method of claim 1 wherein terminating the engine start procedure further comprises:

sending the output signal when the monitored voltage level is below the first voltage threshold.

10. The method of claim 1 wherein performing the engine start procedure further comprises:

sending an output signal when both the monitored voltage level is below the first voltage threshold and the engine does not start during the engine starting procedure; and

terminating the engine starting procedure and sending the output signal when the voltage level is below the first voltage threshold.

11. The method of claim 1 , wherein power is supplied from the external power source until a selected period of time elapses.

12. The method of claim 1 , further comprising sending an output signal to a visual display when the voltage level is below the first voltage threshold.

13. The method of claim 1 , wherein the external power source is electrically coupled to terminals of a second battery, said second battery having a lower voltage then the first battery.

14. The method of claim 1 , wherein the external power source is an external battery.

15. The method of claim 1 further comprising sending an output signal to a vehicle user, wherein the output signal induces a visual signal.

16. A method of externally charging a powertrain comprising:

monitoring a voltage level of a first battery;

comparing the monitored voltage level to first and second voltage thresholds, the first voltage threshold having a higher voltage than the second voltage threshold, wherein the first voltage threshold comprises an overall voltage of the first battery at which the engine may not start due to low overall battery voltage and the second voltage threshold comprises a voltage of the first battery at which it is undesirable to initiate an engine start procedure; and

when the monitored voltage is at least the second voltage threshold,

initiating an engine starting procedure,

sending an output signal to a vehicle user when both the engine starting procedure fails and when the monitored voltage level is below the first voltage threshold in the first battery, and

transferring charge from an external power source to a second battery when the output signal is sent.

17. The method of claim 16 , wherein the second battery has a lower voltage level than the first battery.

18. A method of externally charging a powertrain comprising:

monitoring a power level of a first battery;

comparing the monitored power level to first and second power thresholds, the first power threshold having a higher power than the second power threshold, wherein the first power threshold comprises an overall power of the first battery at which the engine may not start due to low overall battery power and the second power threshold comprises a power of the first battery at which it is undesirable to initiate an engine start procedure; and

when the monitored power is at least the second power threshold,

initiating an engine starting procedure,

sending an output signal to a vehicle user when both the engine starting procedure fails and when the monitored power level is below the first power threshold in the first battery, and

transferring charge from an external power source to a second battery when the output signal is sent.

19. The method of claim 18 , wherein the power is measured based on a voltage measurement and a temperature measurement.