Fuel cell based rechargable power pack system and associated methods for controlling same

• US 20070190369A1
• Filed: 02/14/2006
• Published: 08/16/2007
• Est. Priority Date: 02/14/2006
• Status: Active Grant

• Current Assignee: MTI MicroFuel Cells, Inc. (Soluna Holdings, Inc.)
• Original Assignee: MTI MicroFuel Cells, Inc. (Soluna Holdings, Inc.)
• Inventors: Marvin, Russel, Leach, David
• Granted Patent: US 7,745,025 B2
• Time in Patent Office: Days
• US Class Current: 429/9
• CPC Class Codes: H02J 2300/30 The power source being a fuel cell
• CPC Class Codes: H02J 7/0018 using separate charge circuits
• CPC Class Codes: H02J 7/0019 using switched or multiplexed charge circuits
• CPC Class Codes: H02J 7/00302 Overcharge protection
• CPC Class Codes: H02J 7/00304 Overcurrent protection
• CPC Class Codes: H02J 7/00306 Overdischarge protection
• CPC Class Codes: H02J 7/00308 Overvoltage protection
• CPC Class Codes: H02J 7/34 Parallel operation in networks using both storage and other dc sources, e.g. providing buffering H02J7/14 takes precedence

Abstract

A power pack system for charging a set of isolated batteries is provided. In an illustrative embodiment of the invention, a single fuel cell, a single DC-DC converter and a single system controller device comprises the power-generation side of the power pack. A set of switches is used to connect the power-generation side of the Power pack to one of the isolated batteries in the power pack, thereby recharging that particular battery in the battery power pack set. A battery protection and powerpath control device communicates with the system controller to determine which switches are to be closed depending upon which battery requires recharging. During normal operation the switches will follow the direction from the system controller. If a fault is detected by the battery protection circuit, the protection circuit will take priority and turn off the appropriate switch(es).

Claims

1. A power supply for a battery pack containing two or more isolated batteries, comprising:

a. one or more direct oxidation fuel cells;

b. one or more rechargeable batteries;

c. a DC-DC converter associated with each fuel cell and being coupled to its respective fuel cell so as to receive the output of the fuel cell, and coupled to said battery through an associated battery protection circuit such that said DC-DC converter provides a current to either charge the battery or to power a load; and

d. one or more system controller and balance of plant assembly configured to control operating characteristics of each fuel cell.

2. The power supply as defined in claim 1 having one direct oxidation fuel cell that is coupled to a non-isolated DC-DC converter that is coupled to a first battery, and a second, isolated DC-DC converter that is coupled to a second battery.

3. The power supply as defined in claim 2 wherein said isolated DC-DC converter connected such that it is powered by the first battery.

4. A rechargeable power pack comprising:

a. a fuel cell stack;

b. a DC-DC converter coupled to receive the output of said fuel cell;

c. a first battery and associated battery protection circuit;

d. a second battery and associated battery protection circuit;

e. a system controller and balance of plant assembly configured to receive a signal indicative of a charge characteristic of each battery and to control operating characteristics of said fuel cell; and

f. a switch network defining one or more power paths, such that in a first position, the switch network allows current to flow from the fuel cell to the first battery to charge the battery, and in a second position allows current to the second battery to charge the second battery.

5. The power pack as defined in claim 4 further comprising:

(i) a first set of switches and an associated first voltage sense and switch driver device that is powered by the first battery, and said set of switches in a closed position allowing current to flow from said fuel cell to said first battery to charge said first battery; and

(ii) a second set of switches and an associated second voltage sense and switch driver device that is powered by the second battery, and said second set of switches in a closed position allowing current to flow from said fuel cell to said second battery to charge said second battery.

6. The power pack as defined in claim 5 further comprising:

one or more isolation barriers for carrying digital signals to each of said switch drivers and for feeding the voltages of the first and second batteries, respectively, back to said system controller and balance of plant assembly.

7. The power pack as defined in claim 5 wherein said system controller and balance of plant assembly are powered by a third, internal battery.

8. The power pack as defined in claim 5 wherein said system controller and balance of plant assembly are powered by said second battery.

9. The power pack as defined in claim 5 further comprising an MCU and switch driver coupled to one of said first and second batteries such that programmed to select one of said sets of switches to be closed at a time.

18. The power pack as defined in claim 5 further comprising one or more auxiliary batteries coupled to be charged by said power pack.

19. The power pack as defined in claim 5 further comprising one or more auxiliary batteries coupled to start up said fuel cell.

20. The power pack as defined in claim 9 further comprising a communications bus having clock and data bands for sending information between one or more of the system controller, the switch drivers, the rechargeable battery and the battery protection and powerpath control circuit.

10. A battery protection circuit for use with a power pack containing one or more fuel cells and DC-DC converter, comprising:

a rechargeable battery coupled to receive an output current from said DC-DC converter; and

two current sense resistors coupled to one side of said rechargeable battery so as to define two paths leading to or from said battery, one path leading to a load to be charged and the second path allowing the rechargeable battery to be charged.

11. The battery protection circuit as defined in claim 10 further comprising:

a set of switches placed on either side of said battery such that when said switches are closed, the fuel cell recharges the battery or aides in powering the load.

12. The battery protection circuit as defined in claim 11 further comprising a load switch disposed along the path that is used to power the load such that when the load switch is closed, current flows from the battery to the load through one of the current sense resistances.

13. The battery protection circuit as defined in claim 12 further comprising a bypass switch coupled across the upper voltage rail of said battery such that when the bypass switch is closed, current can flow from said fuel cell to said load, by passing the battery.

14. A battery protection circuit for use with a power pack containing one or more fuel cells and DC-DC converter, comprising:

a rechargeable battery coupled to receive an output current from said DC-DC converter; and

an OEM battery protection circuit having one internal switch and one current sense resistor coupled to one side of said rechargeable battery, and a switch which when closed allow the rechargeable battery power an associated load.

15. The battery protection circuit as defined in claim 14 further comprising

a set of switches placed on either side of said battery such that when said switches are closed, the fuel cell recharges the battery or aides in powering the load.

16. The battery protection circuit as defined in claim 14 further comprising

a load switch disposed along the path that is used to power the load such that when the load switch is closed, current flows from the battery to the load through one of the current sense resistances.

17. The battery protection circuit as defined in claim 14 further comprising a bypass switch coupled across the upper voltage rail of said battery such that when the bypass switch is closed, current can flow from said fuel cell to said load, by passing the battery.

21. A method of maintaining a desired charge on a set of isolated batteries the method comprising the steps of:

providing a fuel cell as a power source;

using a DC-DC converter to adjust the output of said fuel cell to the battery to be charged;

providing two batteries in the power pack each with its own respective battery protection circuit;

measuring an characteristic of each battery including current or voltage;

selecting one of said batteries for recharging based upon a whether the measured characteristic exceeds a threshold value; and

adjusting associated switches in a switch network in said power pack to allow current to flow to the battery to be charged.