Technique and apparatus to measure cell voltages of a fuel cell stack using different ground references

• US 6,281,684 B1
• Filed: 07/31/2000
• Issued: 08/28/2001
• Est. Priority Date: 12/27/1999
• Status: Expired due to Term

• Current Assignee: Plug Power Inc.
• Original Assignee: Plug Power Inc.
• Inventors: James, David E.
• Primary Examiner(s): Tso, Edward H.
• Application Number:
  US09/629,003
• Time in Patent Office: 393 Days
• Field of Search: 320/116, 320/117, 320/119, 320/120, 320/122, 320/FOR.114, 320/FOR.116, 324/425, 324/426, 324/430, 324/433, 324/434
• US Class Current: 324/434
• CPC Class Codes: G01R 19/16542 for batteries charge condition monitoring in G01R31/36
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/3835 involving only voltage measurements
• CPC Class Codes: G01R 31/396 Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A system that is usable with a stack of fuel cells that have cell terminals includes a circuit and scanning units. The circuit provides a selection signal that indicates selection of at least one of the fuel cells for a voltage measurement. The scanning units are coupled to the stack to establish different groups of the fuel cells. Each group is associated with a different one of the scanning units, and each scanning unit has a ground that is referenced to a different one of the cell terminals. Each scanning unit is adapted to, in response to the selection signal, measure and indicate a voltage of each selected fuel cell within the group of fuel cells associated with the scanning unit.

Claims

1. A system usable with a stack of fuel cells that have cell terminals, comprising:

a circuit to provide a selection signal indicating selection of at least one of the fuel cells for a voltage measurement; and

scanning units adapted to be coupled to the stack to establish different groups of the fuel cells, each group being associated with a different one of the scanning units and each scanning unit having a ground referenced to a different one of the cell terminals and being adapted to in response to the selection signal, measure and indicate a voltage of each selected fuel cell within the group of fuel cells associated with said each scanning unit.

2. The system of claim 1, wherein each state of the selection signal selects fuel cells from different groups.

3. The system of claim 1, wherein the circuit comprises a microprocessor.

5. The system of claim 1, wherein the circuit and the stack have a common ground connection.

6. The system of claim 1, wherein the ground of at least one of the scanning units is connected to the cell terminal of one of the cells in the associated group.

7. The system of claim 1, wherein at least one of the scanning unit s has an associated maximum input voltage that is less than the voltage of at least one of the terminals of the associated group with respect to a ground of the fuel cell stack.

8. The system of claim 7, wherein the maximum input voltage is between approximately 16 to 30 volts.

9. The system of claim 1, further comprising:

voltage regulators, each regulator providing power to at least one of the scanning units and having a ground in common with the ground associated with one of said at least one of the scanning units.

10. The system of claim 1, wherein at least one of the scanning units comprises:

a differential amplifier adapted to measure the voltages of the fuel cells in the associated group and provide an analog signal indicating the measurements; and

multiplexing circuitry to, in response to the selection signal indicating one of the fuel cells in the associated group, selectively couple the terminals of the fuel cell indicated by the selection signal to the differential amplifier.

11. The system of claim 10, wherein said at least one of the scanning units further comprises:

optical isolation circuitry to communicate the analog signal to the circuit.

12. The system of claim 1, wherein said at least one of the scanning units does not comprise a microprocessor.

4. The system of claim, wherein each scanning unit furnishes a different analog signal to indicate the measured voltage, the system further comprising:

an analog to digital converter to convert the analog signals into digital indications of the measured voltages.

13. A system usable with a serially coupled array of voltage sources that have terminals, comprising:

a circuit to provide a selection signal indicating selection of at least one of the voltage sources for a voltage measurement; and

scanning units adapted to be coupled to the array to establish different groups of the voltage sources, each group being associated with a different one of the scanning units and each scanning unit having a ground referenced to a different one of the terminals and being adapted to in response to the selection signal, measure and indicate a voltage of each selected voltage source within the group of voltage sources associated with said each scanning unit.

14. The system of claim 13, wherein each state of the selection signal selects voltage sources from different groups.

15. The system of claim 13, wherein the circuit comprises a microprocessor.

16. The system of claim 13, wherein each scanning unit furnishes a different analog signal to indicate the measured voltage, the system further comprising:

an analog to digital converter to convert the analog signals into digital indications of the measured voltages.

17. The system of claim 13, wherein the circuit and the array have a common ground connection.

18. The system of claim 13, wherein the ground of at least one of the scanning units is connected to the terminal of one of the voltage sources in the associated group.

19. The system of claim 13, wherein at least one of the scanning units has an associated maximum input voltage that is less than the voltage of at least one of terminals of the associated group with respect to a ground of the array.

20. The system of claim 13, wherein the array comprises a fuel cell stack.

21. The system of claim 13, wherein the array comprises a battery bank.

22. The system of claim 13, further comprising:

voltage regulators, each regulator providing power to at least one of the scanning units and having a ground in common with the ground associated with one of said at least one of the scanning units.

23. The system of claim 13, wherein at least one of the scanning units comprises:

a differential amplifier adapted to measure the voltages of the voltage sources in the associated group and provide an analog signal indicating the measurements; and

multiplexing circuitry to, in response to the selection signal indicating one of the voltage sources in the associated group, selectively couple the terminals of the voltage source indicated by the selection signal to the differential amplifier.

24. The system of claim 23, wherein said at least one of the scanning units further comprises:

optical isolation circuitry to communicate the analog signal to the circuit.

25. A method usable with a stack of fuel cells, comprising:

dividing the fuel cells into groups;

establishing ground references at the different terminals of the cells, each ground reference being associated with one of the groups;

providing a selection signal to scanning units associated with the groups, the selection signal indicating selection of at least one of the cells; and

in response to the selection signal, using at least one of the scanning units to measure the one or more voltages of said at least one of the cells indicated by the selection signal.

26. The method of claim 25, wherein the ground reference that is associated with at least one of the scanning units is connected to the terminal of one of the cells in the associated group.

27. The method of claim 25, wherein the act of measuring comprises:

measuring the voltages one at a time.

28. The method of claim 25, wherein the act of measuring comprises:

concurrently measuring the voltages of fuel cells of different groups in response to the selection signal.

29. The method of claim 25, wherein the act of measuring comprises:

concurrently measuring the voltages of fuel cells of all of the groups in response to the selection signal.