Electrical load management system and method

1. An electrical load management system for charging batteries, comprising:

an electrical power input configured to couple the load management system with a common power source;

a plurality of electrical power outputs configured to couple the load management system with a plurality of electrical loads, each electrical load comprising a battery to be charged;

a plurality of switches coupled between the power input and the power outputs;

a first current sensor coupled to the power outputs for sensing a current drawn by one or more of the power outputs; and

a controller coupled to the plurality of switches and the first current sensor, the controller configured to:

determine a switched current limit defining a limit for current drawn by the electrical power outputs;

carry out an iterative grouping process in which the controller is configured to

measure with the first current sensor a current drawn by each of a plurality of electrical loads respectively coupled to the plurality of electrical power outputs, each electrical load comprising a battery to be charged,

group the plurality of power outputs and respective electrical loads into a plurality of load groups such that a sum of the measured currents of the electrical loads in each load group does not exceed the switched current limit, the grouping comprising

forming a first load group with a maximum number of the power outputs and respective electrical loads,

then forming a second load group with a maximum number of the power outputs and respective electrical loads not in the first load group, and

then continuing to form additional load groups as long as any of the power outputs and respective electrical loads remain ungrouped, each successive additional load group having a maximum number of the currently ungrouped power outputs and respective electrical loads,

operate the plurality of switches to apply electrical power from the common power source to each of the load groups to charge the batteries forming at least part of the electrical loads within each of the load groups, and to apply the electrical power to only one load group at a time while removing the electrical power from the other load groups, and

restart the iterative grouping process after applying electrical power to each of the load groups; and

continue the iterative grouping process at least until all of the plurality of power outputs and respective electrical loads are combined in one load group.

2. The system of claim 1 , further comprising an indicator coupled to the controller, wherein the controller is configured to activate the indicator based on a state of the system.

3. The system of claim 1 , further comprising a temperature sensor coupled to the controller, wherein the controller is further configured to receive a temperature signal from the temperature sensor and activate one or more of the plurality of switches to turn off one or more of the power outputs based on the temperature signal.

4. The system of claim 1 , wherein the electrical power input is configured to couple the load management system with an alternating current (AC) power source, the plurality of switches are configured to switch AC power, and the plurality of electrical power outputs are configured to couple the load management system with a plurality of electrical loads requiring AC power.

5. The system of claim 1 , wherein the electrical power input is configured to couple the load management system with a direct current (DC) power source, the plurality of switches are configured to switch DC power, and the plurality of electrical power outputs are configured to couple the load management system with a plurality of electrical loads requiring DC power.

6. The system of claim 1 , further comprising an un-switched power output coupled to the electrical power input and a second current sensor coupled to the controller, the un-switched power output configured to couple the load management system with a corresponding un-switched electrical load and the second current sensor configured to sense a current drawn by the un-switched power output.

7. The system of claim 6 , wherein the controller is configured to measure with the second current sensor a current drawn by the un-switched electrical load and determine the switched current limit based on the measured current drawn by the un-switched electrical load.

8. The system of claim 7 , wherein the controller is configured to measure the current drawn by the un-switched electrical load and determine the switched current limit before starting the iterative grouping process.

9. The system of claim 8 , wherein the controller is further configured to

determine the current drawn by the un-switched electrical load during the iterative grouping process; and

if the determination of the current indicates an increase in the current drawn by the un-switched load, then

interrupt the iterative grouping process,

re-determine the switched current limit based on the increase in the current drawn by the un-switched load, and

restart the iterative grouping process using the re-determined switched current limit.

10. The system of claim 1 , wherein the controller is further configured to measure the current drawn by each of the plurality of electrical loads throughout the iterative grouping process, and if the measured currents indicate that an increase in the current drawn by the electrical loads within a load group is above the switched current limit, then interrupt and restart the iterative grouping process.

11. The system of claim 1 , wherein the controller applying the electrical power to only one load group at a time comprises applying the electrical power to each load group for a predetermined period of time.

12. The system of claim 1 , wherein the controller applying the electrical power to only one load group at a time comprises applying the electrical power to the load groups according to a power sequence.

13. The system of claim 12 , wherein the power sequence is based on the number of power outputs and respective electrical loads within each load group or on a current draw of each load group.

14. The system of claim 13 , wherein the power sequence is from a load group having the largest number of electrical loads to a load group having the least number of electrical loads.

15. The system of claim 13 , wherein the power sequence is from a load group having the largest current draw to a load group having the smallest current draw.

16. A battery charging station, comprising:

an electrical power input configured to couple the charging station with a common power source;

a plurality of switched electrical power outputs configured to couple the charging station with a plurality of electrical loads comprising batteries to be charged;

a plurality of switches coupled between the power input and the switched power outputs;

a first current sensor coupled to the switched power outputs for sensing a current drawn by one or more of the switched power outputs;

an un-switched power output coupled to the electrical power input and configured to couple the charging station with an un-switched electrical load;

a second current sensor coupled to the un-switched power output for sensing a current drawn by the un-switched power output; and

a controller coupled to the plurality of switches, the first current sensor, and the second current sensor, the controller configured to:

determine a switched current limit based on the current drawn by the un-switched power output and a current limit of the common power source;

carry out an iterative grouping process in which the controller is configured to

measure with the first current sensor a current drawn by each of the electrical loads respectively coupled to the switched power outputs, each electrical load comprising a battery to be charged,

group the plurality of switched power outputs and respective electrical loads into a plurality of load groups such that a sum of the measured currents of the electrical loads in each load group does not exceed the switched current limit, comprising

forming a first load group with a maximum number of the switched power outputs and respective electrical loads,

then forming a second load group with a maximum number of the switched power outputs and respective electrical loads not in the first load group, and

then continuing to form additional load groups as long as any of the switched power outputs and respective electrical loads remain ungrouped, each successive additional load group having a maximum number of the currently ungrouped power outputs and respective electrical loads,

operate the plurality of switches to apply electrical power from the common power source to each of the load groups to charge the batteries forming at least part of the electrical loads within each of the load groups, and to apply the electrical power to only one load group at a time while removing the electrical power from the other load groups, and

restart the iterative grouping process after applying electrical power to each of the load groups; and

continue the iterative grouping process at least until all of the plurality of switched power outputs and respective electrical loads are combined in one load group.

17. The charging station of claim 16 , wherein the controller is configured to measure with the second current sensor the current drawn by the un-switched power output before starting the iterative grouping process.

18. The charging station of claim 17 , wherein the controller is further configured to

determine the current drawn by the un-switched power output during the iterative grouping process; and

if the determination of the current indicates an increase in the current drawn by the un-switched power output, then

interrupt the iterative grouping process,

re-determine the switched current limit based on the increase in the current drawn by the un-switched load, and

restart the iterative grouping process using the re-determined switched current limit.

19. The charging station of claim 16 , wherein the controller is further configured to measure the current drawn by each of the switched power outputs throughout the iterative grouping process, and if the measured currents indicate that an increase in the current drawn by the switched power outputs within a load group is above the switched current limit, then interrupt and restart the iterative grouping process.

20. The charging station of claim 16 , wherein the plurality of electrical loads to be charged comprise at least one of a notebook computer, a tablet computer, a cell phone, a smart phone, a personal digital assistant, a camera, a music player, and a global positioning satellite device.

21. The charging station of claim 16 , wherein the charging station comprises a notebook charging cart.

22. The charging station of claim 16 , wherein the charging station comprises a stationary battery charging station.

23. The charging station of claim 16 , wherein the controller applying the electrical power to only one load group at a time comprises applying the electrical power to each load group for a predetermined period of time according to a power sequence.

24. The charging station of claim 23 , wherein the power sequence is from a load group having the largest number of electrical loads to a load group having the least number of electrical loads or from a load group having the largest current draw to a load group having the smallest current draw.

25. A method for distributing electrical power to electrical loads for charging batteries, comprising:

determining a switched current limit defining a limit for current drawn by a plurality of electrical loads coupled to a common power source through a load management system;

carrying out an iterative grouping process, comprising:

measuring a current drawn by each of the plurality of electrical loads, each electrical load comprising a battery to be charged;

forming a first load group comprising a maximum number of the electrical loads without a sum of the measured currents of the electrical loads in the first load group exceeding the switched current limit;

then forming a second load group comprising a maximum number of the electrical loads not in the first load group without a sum of the measured currents of the electrical loads in the second load group exceeding the switched current limit; and

then continuing to form additional load groups as long as any of the electrical loads remain ungrouped, each successive additional load group having a maximum number of the currently ungrouped electrical loads without a sum of the measured currents of the electrical loads exceeding the switched current limit;

charging the batteries within each of the first, second, and additional load groups by switching electrical power from the common power source to each of the load groups thereby applying the electrical power to only one load group at a time while removing the electrical power from the other load groups; and

restarting the iterative grouping process after charging the batteries within each load group; and

continuing the iterative grouping process at least until all of the plurality of electrical loads are combined in one load group.

26. The method of claim 25 , wherein measuring the current drawn by each of the plurality of electrical loads comprises applying electrical power to one electrical load at a time.

27. The method of claim 25 , further comprising applying electrical power through the load management system to an un-switched electrical load simultaneously with charging the batteries within each of the first, second, and additional load groups during the iterative grouping process.

28. The method of claim 27 , further comprising measuring a current drawn by the un-switched electrical load, and determining the switched current limit based on the measured current drawn by the un-switched electrical load.

29. The method of claim 28 , further comprising measuring the current drawn by the un-switched electrical load before starting the iterative grouping process.

30. The method of claim 28 , further comprising measuring the current drawn by the un-switched electrical load during the iterative grouping process; and

if the measuring of the current indicates an increase in the current drawn by the un-switched load, then

interrupting the iterative grouping process;

re-determining the switched current limit based on the increase in the current drawn by the un-switched load; and

restarting the iterative grouping process using the re-determined switched current limit.

31. The method of claim 27 , further comprising determining the switched current limit based on a current limit of the common power source.

32. The method of claim 25 , further comprising measuring the current drawn by each of the plurality of electrical loads throughout the iterative grouping process, and if the measured currents indicate an increase in the current drawn by the electrical loads within a load group above the switched current limit, then interrupting and restarting the iterative grouping process.

33. The method of claim 25 , wherein the load management system is part of a charging station for charging notebook computers.

34. The method of claim 33 , wherein the charging station comprises a notebook charging cart.

35. The method of claim 25 , wherein charging the batteries by applying the electrical power to only one load group at a time comprises applying the electrical power to each of the load groups for a predetermined period of time according to a power sequence based on at least one of a current draw of each load group and the number of electrical loads within each load group.