System and method for managing distribution of vehicle power in a multiple battery system

1. In a vehicle comprising a crank battery, a rechargeable auxiliary battery, and an onboard electrical power source separate from said crank battery and said auxiliary battery, a battery charge controller for managing a supply of electrical energy to said auxiliary battery to charge said auxiliary battery, said battery charge controller comprising:

means for monitoring a voltage level of said crank battery;

means for monitoring a voltage level of said onboard electrical power source;

means for electrically coupling said crank battery and said auxiliary battery to charge said auxiliary battery when the voltage level of said crank battery exceeds a first voltage threshold, and for electrically decoupling said crank battery and said auxiliary battery when the voltage level of said crank battery is below said first voltage threshold; and

means for electrically coupling said onboard power source and said auxiliary battery to charge said auxiliary battery when: (i) the voltage level of said crank battery is below said first voltage threshold and (ii) the voltage level of said onboard power source exceeds a second voltage threshold, and for electrically decoupling said onboard power source and said auxiliary battery when the voltage level of said onboard power source is below said second voltage threshold.

2. A battery charge controller according to claim 1 , wherein said first voltage threshold is greater than 12.2 volts.

3. A battery charge controller according to claim 2 , wherein said second voltage threshold is greater than 13.2 volts.

4. A battery charge controller according to claim 1 , wherein said onboard electrical power source comprises an electrical system of an onboard refrigeration unit.

5. A battery charge controller according to claim 4 , wherein the electrical system of said refrigeration unit comprises a battery and an alternator.

6. A battery charge controller according to claim 1 , wherein said means for electrically coupling said crank battery and said auxiliary battery, and for electrically coupling said onboard power source and said auxiliary battery comprises at least one switching device.

7. A battery charge controller according to claim 6 , wherein said switching device comprises a relay.

8. A battery charge controller according to claim 1 , wherein said means for monitoring a voltage level of said crank battery, and for monitoring a voltage level of said onboard electrical power source comprises a microprocessor-based control module.

9. A battery charge controller according to claim 1 , wherein said rechargeable auxiliary battery is electrically connected to a vehicle liftgate.

10. In a heavy duty vehicle comprising a tractor/trailer combination, a vehicle power line electrically interconnecting said tractor and said trailer, a crank battery carried by said tractor and electrically connected to said vehicle power line, a rechargeable auxiliary battery carried by said trailer, a voltage converter carried by said trailer and electrically connected to said auxiliary battery, and an onboard electrical power source carried by said trailer and separate from said crank battery, said auxiliary battery, and said voltage converter, a charge controller for managing a supply of electrical energy to said voltage converter to charge said auxiliary battery, said charge controller comprising:

means for monitoring a voltage level of said crank battery;

means for monitoring a voltage level of said onboard electrical power source;

means for electrically coupling said crank battery and said voltage converter to charge said auxiliary battery when the voltage level of said crank battery exceeds a first voltage threshold, and for electrically decoupling said crank battery and said voltage converter when the voltage level of said crank battery is below said first voltage threshold; and

means for electrically coupling said onboard power source and said voltage converter to charge said auxiliary battery when: (i) the voltage level of said crank battery is below said first voltage threshold and (ii) the voltage level of said onboard power source exceeds a second voltage threshold, and for electrically decoupling said onboard power source and said voltage converter when the voltage level of said onboard power source is below said second voltage threshold.

11. A battery charge controller according to claim 10 , wherein said vehicle power line comprises a plurality of electrical conductors, and a multi-pin connector interconnecting conductors of said tractor and said trailer.

12. A battery charge controller according to claim 11 , wherein said connector comprises a SAE J560 seven-pin connector.

13. A battery charge controller according to claim 10 , wherein said first voltage threshold is greater than 12.2 volts.

14. A battery charge controller according to claim 13 , second voltage threshold is greater than 13.2 volts.

15. A battery charge controller according to claim 10 , wherein said onboard electrical power source comprises an electrical system of an onboard refrigeration unit.

16. A battery charge controller according to claim 15 , wherein the electrical system of said refrigeration unit comprises a battery and an alternator.

17. A battery charge controller according to claim 10 , wherein said means for electrical coupling said crank battery and said voltage converter, and for electrically coupling said onboard power source and said voltage converter comprises at least one switching device.

18. A battery charge controller according to claim 17 , wherein said switching device comprises a relay.

19. A battery charge controller according to claim 10 , wherein said means for monitoring a voltage level of said crank battery, and for monitoring a voltage level of said onboard electrical power source comprises a microprocessor-based control module.

20. A battery charge controller according to claim 10 , wherein said rechargeable auxiliary battery is electrically connect to a vehicle liftgate.