Hybrid energy storage device charge equalization system and method
First Claim
1. A hybrid power supply system for supplying electrical power to a load comprising:
- (a) a power generating device;
(b) a first energy storage device chargeable by said power generating device and electrically connectable to said load;
(c) a first detector for measuring the state of charge of said first energy storage device;
(d) a second energy storage device chargeable by said power generating device and electrically connectable to said first energy storage device; and
(e) a controller for receiving input from said first detector, wherein said controller causes said second energy storage device to provide an equalization current to said first energy storage device when said controller detects a first predetermined state of charge condition.
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Abstract
A system and method for improving the performance of a hybrid power supply apparatus comprising a power generating device, such as a fuel cell, and a primary energy storage device, such as a battery. The purpose of the invention is to provide an equalization charge to the battery from a source other than the fuel cell when the battery achieves a predetermined state of charge condition, thereby avoiding the need to operate the fuel cell in a low power output mode. When the predetermined state of charge condition is detected by a controller, the fuel cell is shut-down. In one aspect of the invention the equalization charge is provided to the battery by a secondary energy storage device, such as a plurality of capacitors or secondary batteries. The predetermined state of charge condition may be satisfied, for example, when the state of charge of the battery exceeds a predetermined threshold, such as 80% of the battery'"'"'s storage capacity, for a predetermined period of time. In some aspects of the invention, the secondary energy storage device may also be connectable to the load. Preferably the system also includes a DC/DC converter for regulating current flow between the fuel cell and the storage devices.
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Citations
37 Claims
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1. A hybrid power supply system for supplying electrical power to a load comprising:
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(a) a power generating device;
(b) a first energy storage device chargeable by said power generating device and electrically connectable to said load;
(c) a first detector for measuring the state of charge of said first energy storage device;
(d) a second energy storage device chargeable by said power generating device and electrically connectable to said first energy storage device; and
(e) a controller for receiving input from said first detector, wherein said controller causes said second energy storage device to provide an equalization current to said first energy storage device when said controller detects a first predetermined state of charge condition. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. A method of operating a hybrid power supply apparatus including a power generating device adjustable between charging and shut-down modes and further including first and second energy storage devices chargeable by said power generating device, at least one of the first and second energy storage devices being connected to a load for delivering electrical power thereto, said method comprising:
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(a) operating said power generating device in said charging mode to deliver charging current to said first and second energy storage devices;
(b) repeatedly measuring the state of charge of said first energy storage device;
(c) adjusting said power generating device from said charging mode to said shut-down mode when the measured state of charge of said first energy storage device satisfies a first predetermined state of charge condition; and
(d) providing an equalization current from said second energy storage device to said first energy storage device while said power generating device is in said shut-down mode until the measured state of charge of said first energy storage device reaches approximately its full storage capacity. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32, 33, 34)
(e) adjusting said power generating device from said shut-down mode to said charging mode when the measured state of charge of said first energy storage device is below a second threshold value for a predetermined period of time.
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27. The method of claim 24, wherein both of said first and second energy storage devices are electrically connectable to said load for delivering electrical power thereto and wherein said method further comprises:
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(e) adjusting said power generating device from said shut-down mode to said charging mode when the measured state of charge of said first energy storage device is below a second threshold value for a predetermined period of time;
(f) repeatedly measuring the state of charge of said second energy storage device;
(g) delivering a pre-charge current from said power generating device or said first energy storage device to said second energy storage device; and
(h) electrically connecting said second energy storage device to said load when the measured state of charge of said second energy storage device exceeds a third threshold value for a predetermined period of time.
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28. The method of claim 27, wherein said third threshold value is a state of charge approximately equal to the state of charge of said first energy storage device when said states of charge of said first and second energy storage devices are measured simultaneously.
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29. The method of claim 27, wherein said first and second energy storage devices are charged simultaneously.
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30. The method of claim 29, wherein said first and second energy storage devices are discharged simultaneously.
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31. The method of claim 24, wherein said power generating device comprises a fuel cell and said apparatus further comprises a DC/DC converter for delivering current from said fuel cell to at least said first energy storage device.
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32. The method of claim 31, further comprising connecting the output of said second energy storage device to the input of said DC/DC converter when the measured state of charge of said first energy storage device exceeds said first threshold value for a predetermined period of time.
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33. The method of claim 27, wherein said power generating device is adjusted from said charging mode to said shut-down mode when the combined states of charge of said first and second energy storage devices exceed a predetermined amount.
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34. The method of claim 27, wherein said apparatus is operable in successive alternating first and second operating cycles, wherein said second energy storage device delivers an equalization current to said first energy storage device when said power generating device is in said shut-down mode in said first operating cycle, and wherein said first energy storage device delivers an equalization current to said second energy storage device when said power generating device is in said shut-down mode in said second operating cycle.
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35. A hybrid power supply system for supplying electrical power to a load comprising:
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(a) a power generating device operable in alternating charging and non-charging modes;
(b) a first energy storage device chargeable by said power generating device and electrically connectable to said load;
(c) a first detector for measuring the state of charge of said first energy storage device;
(d) a second energy storage device chargeable by said power generating device and electrically connectable to said first energy storage device; and
(e) a controller for receiving input from said first detector, wherein said controller causes said second energy storage device to provide an equalization current to said first energy storage device when said controller detects a first predetermined state of charge condition, and wherein said controller causes said power generating device to switch from said charging mode to said non-charging mode when said first predetermined state of charge condition is detected. - View Dependent Claims (36)
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37. A method of operating a hybrid power supply apparatus including a power generating device adjustable between charging and non-charging modes and further including first and second energy storage devices chargeable by said power generating device, at least one of the first and second energy storage devices being connected to a load for delivering electrical power thereto, said method comprising:
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(a) operating said power generating device in said charging mode to deliver charging current to said first and second energy storage devices;
(b) repeatedly measuring the state of charge of said first energy storage device;
(c) adjusting said power generating device from said charging mode to said non-charging mode when the measured state of charge of said first energy storage device satisfies a first predetermined state of charge condition; and
(d) providing an equalization current from said second energy storage device to said first energy storage device while said power generating device is in said non-charging mode until the measured state of charge of said first energy storage device reaches approximately its full storage capacity.
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Specification