Back-up battery management apparatus and method for charging and testing battery cells in a string of battery cells

• US 6,583,603 B1
• Filed: 02/08/2002
• Issued: 06/24/2003
• Est. Priority Date: 02/08/2002
• Status: Expired due to Fees

• Current Assignee: PECO II, Inc. (GE Aerospace)
• Original Assignee: PECO II, Inc. (GE Aerospace)
• Inventors: Baldwin, Norman C.
• Primary Examiner(s): Tso, Edward H.
• Assistant Examiner(s): TIBBITS, PIA FLORENCE
• Application Number:
  US10/071,052
• Time in Patent Office: 501 Days
• Field of Search: 320/116, 320/118, 320/121, 320/122, 320/134, 320/136, 324/426, 324/427, 324/429, 324/430, 324/434, 307/19, 307/46, 307/47, 307/65, 307/66
• US Class Current: 320/121
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• 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: H02J 7/0013 acting upon several batteries simultaneously or sequentially H02J7/1423 takes precedence
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]
• CPC Class Codes: H02J 7/005 Detection of state of health [SOH]

Abstract

An apparatus and method for controllably charging and discharging individual battery cells or groups of battery cells in a string of batteries employed as a back-up power supply is provided. The apparatus includes battery supply modules for at least partially isolating battery strings from the load bus and primary power supply. The partial isolation is effected by a switching network including two controlled switches arranged in parallel to selectively isolate the string of batteries. In certain disclosed embodiments, one of the controlled switches is turned on to connect the string of batteries to the load bus until the other controlled switch closes. The system includes a main power supply that supplies a power bus to a regulator in each battery supply module, which is used for charging the battery string, and a discharge bus to each battery supply module for discharging the batteries.

Claims

1. An apparatus for selectively charging and testing battery cells in one or more strings of battery cells electrically connected to one another within each string and employed as a back-up power supply for a primary power source, the one or more strings of battery cells selectively connectable to a load bus supplied by the primary power source in order to deliver power in the event of a failure of the primary power source, the apparatus comprising:

a main control module having a first power supply for supplying a charging power bus and a discharge bus; and

one or more battery string modules each connected to a respective string of battery cells of the one or more strings of battery cells and to the load bus and configured to selectively electrically isolate the respective string of battery cells from the load bus, each of the one or more battery string modules having;

a regulator configured to receive charging power from the first power supply via the charging power bus, and supply and regulate charging power to the respective string of battery cells;

a controllable impedance;

a first controllable switch electrically connected in parallel with the controllable impedance, wherein the parallel combination of the controllable impedance and the first controllable switch is connected in series between the load bus and the corresponding string of battery cells; and

a first controller configured to selectively control the controllable impedance and the first controllable switch, wherein the first controller detects when a voltage of the load bus is falling and subsequently initiates operation of the controllable impedance and the first controllable switch simultaneously, wherein the controllable impedance is operated for a predetermined time period.

2. An apparatus as defined in claim 1, wherein the predetermined time period is selected dependent on the closing time of the first controllable switch.

3. An apparatus as defined in claim 2, wherein the predetermined time period is less than 200 milliseconds.

4. An apparatus as defined in claim 1 wherein the controllable impedance is an SCR and the first controllable switch is a normally closed relay.

5. An apparatus as defined in claim 1 wherein each of the battery string modules is configured to selectively provide a float current to a corresponding string of battery cells.

6. An apparatus as defined in claim 5, wherein the float current delivered to the string of battery cells is regulated by the first controller through the regulator.

7. An apparatus as defined in claim 1, wherein the main control module further comprises a second controller that is configured to monitor and control levels of voltage and current output by first power supply on the charging power bus and at least control a voltage of the discharge bus.

8. An apparatus as defined in claim 7, wherein voltage delivered by the first power supply on the charging power bus is regulated by the second controller to a prescribed value based on a predetermined head room needed by the regulators in each of the battery string modules such that heat generated by the regulators is maintained at or below a desired heat generation level.

9. An apparatus as defined in claim 1 wherein each of the battery string modules further includes a second controllable switch that is controlled by the first controller and selectively electrically connects the corresponding battery string to the discharge bus during testing of the battery string.

10. An apparatus as defined in claim 9, wherein voltage output by the first power supply on the discharge bus is regulated by the second controller to a prescribed value such that a voltage of the main bus does not rise beyond a prescribed range when a loading of the main bus is reduced below a discharge test current limit and the battery string is connected to the discharge bus through the second controllable switch.

11. An apparatus as defined in claim 10, wherein the second controllable switch is a FET.

12. An apparatus as defined in claim 1, wherein the first controller is configured to effect charging of the battery string from the main power supply through the main bus through the first controllable switch until prescribed transition conditions occur.

13. An apparatus as defined in claim 12, wherein when the prescribed transition conditions occur, the first controller opens the first controllable switch and initiates boost charging of the battery string using the regulator to supply a boost current to the battery string.

14. An apparatus as defined in claim 13 wherein the regulation of the boost current delivered to the battery string is at least partially based on temperature.

15. An apparatus as defined in claim 12, wherein the prescribed transition conditions include the charging current of the battery string decreasing to a value, which is a prescribed fraction of a set boost current value, and a voltage level of the main bus greater than a loss of bus detection value.

16. An apparatus as defined in claim 15, wherein the prescribed fraction is approximately two-thirds.

17. An apparatus as defined in claim 1, wherein the first controller is configured to initiate operation of the controllable impedance and the first controllable switch when the first controller detects that a voltage level of the main bus falls below a predetermined loss of bus detection value.

18. An apparatus as defined in claim 1, wherein the first controller is configured to control the regulator to provide a float current to the battery string in order to maintain a predetermined level of charge in the battery string.

19. An apparatus as defined in claim 18 wherein the regulation of the float current delivered to the battery strings is at least partially based on temperature.

20. An apparatus as defined in claim 19, wherein the controller is configured to control the regulator to provide a float current to the battery string in order to maintain a predetermined level of charge in the battery string.

21. An apparatus as defined in claim 20 wherein the regulation of the float current delivered to the battery strings is at least partially based on temperature.

22. An apparatus for selectively charging and testing battery cells in a serial string of battery cells and employed as part of a back-up power supply to a primary power source that supplies power to a main bus connected to a load, the apparatus comprising:

a regulator configured to receive charging power from an external power supply via a charging power bus, and supply and regulate charging power to the string of battery cells;

a variable impedance;

a first controllable switch electrically connected in parallel with the variable impedance, wherein the parallel combination of the variable impedance and the first controllable switch is connected in series between the load bus and the corresponding string of battery cells; and

a controller configured to selectively control the variable impedance and the first controllable switch, wherein the controller is configured to detect when a voltage of the main bus is falling and subsequently initiate operation of the variable impedance and the first controllable switch simultaneously, wherein the variable impedance is operated for a predetermined time period.

23. An apparatus as defined in claim 22, wherein the predetermined time period is selected dependent on the closing time of the first controllable switch.

24. An apparatus as defined in claim 23, wherein the predetermined time period is less than 200 milliseconds.

25. An apparatus as defined in claim 22, wherein the variable impedance is an SCR and the first controllable switch is a normally closed relay.

26. An apparatus as defined in claim 22 wherein the regulator selectively provides a float current to the string of battery cells as determined by the controller.

27. An apparatus as defined in claim 26 wherein the float current delivered to the string of battery cells is regulated by the controller.

28. An apparatus as defined in claim 22 further comprising:

a second controllable switch that is controlled by the controller and selectively electrically connects the battery string to a discharge bus during testing of the battery string.

29. An apparatus as defined in claim 28, wherein the second controllable switch is a FET.

30. An apparatus as defined in claims 22, wherein the controller is configured to effect charging of the battery string from the primary power source via the main bus through the first controllable switch until prescribed transition conditions occur.

31. An apparatus as defined in claim 30, wherein when the prescribed transition conditions occur, the controller opens the first controllable switch and initiates boost charging of the battery string using the regulator by supplying a boost current to the battery string.

32. An apparatus as defined in claim 31 wherein the regulation of the boost current delivered to the battery string is at least partially based on temperature.

33. An apparatus as defined in claim 30, wherein the prescribed transition conditions include the charging current of the battery string decreasing to a value that is a predetermined fraction of a boost current value and a voltage level of the main bus greater than a loss of bus detection value.

34. An apparatus as defined in claim 22, wherein the controller is configured to initiate operation of the variable impedance and the first controllable switch when the controller detects that a voltage level of the main bus falls below a predetermined loss of bus detection value.

35. A method for selectively charging and testing battery cells in one or more strings of battery cells electrically connected to one another within each string and employed as a back-up power supply for a primary power source, the one or more strings of battery cells selectively connectable to a load bus supplied by the primary power source in order to deliver power in the event of a failure of the primary power source, the method comprising:

providing a charging power and discharging voltage using a first power supply in a main control module; and

selectively isolating the one or more strings of battery cells from the load bus using a combination of a controllable impedance and a first controllable switch both controlled by a first controller located within a corresponding battery string module connected to a respective string of battery cells of the one or more strings of battery cells;

selectively receiving charging power at each of the battery string modules from the first power supply via the charging power bus;

supplying and regulating charging power to the respective string of battery cells with each of the battery string modules;

detecting when a voltage of the load bus is falling using the first controller; and

initiating operation of the controllable impedance and the first controllable switch simultaneously, wherein the controllable impedance is operated for a predetermined time period.

36. A method as defined in claim 35, wherein the predetermined time period is selected dependent on the closing time of the first controllable switch.

37. A method as defined in claim 36, wherein the predetermined time period is less than 200 milliseconds.

38. A method as defined in claim 35 wherein the controllable impedance is an SCR and the first controllable switch is a normally closed relay.

39. A method as defined in claim 35 further comprising:

selectively providing a float current to a corresponding string of battery cells within each of the battery string modules.

40. A method as defined in claim 39 wherein the float current delivered to the string of battery cells is regulated by control of the first controller.

41. A method as defined in claim 35, further comprising:

monitoring and selectively controlling levels of voltage and current of the charging power output by first power supply through the use of a second controller; and

controlling the discharging voltage using the second controller.

42. A method as defined in claim 41, wherein the voltage of the charging power delivered by the first power supply is regulated by the second controller to a prescribed value based on a predetermined head room needed by regulators in each of the battery string modules such that heat generated by the regulators is maintained at or below a desired heat generation level.

43. A method as defined in claim 35 further comprising:

selectively connecting the one or more battery strings to the discharge voltage during testing of the corresponding battery string through a second controllable switch that is controlled by the first controller.

44. A method as defined in claim 43, wherein the discharge voltage is regulated by the second controller to a prescribed value such that a voltage of the main bus does not rise beyond a prescribed range when a loading of the main bus is reduced below a discharge test current limit and the battery string is connected to the discharge bus through the second controllable switch.

45. A method as defined in claim 43, wherein the second controllable switch is a FET.

46. A method as defined in claim 35, further comprising:

effecting charging of the one or more battery strings from the main power supply via the main bus through the respective first controllable switch under control of the corresponding first controller until prescribed transition conditions occur.

47. A method as defined in claim 46, wherein when the prescribed transition conditions occur, the first controller opens the first controllable switch and initiates boost charging of the battery string using a regulator withing the corresponding battery string module to supply a boost current to the battery string.

48. A method as defined in claim 47 wherein the regulation of the boost current delivered to the battery string is at least partially based on temperature.

49. A method as defined in claim 46, wherein the prescribed transition conditions include the charging current of the battery string decreasing to a value, which is a prescribed fraction of a set boost current value, and a voltage level of the main bus greater than a loss of bus detection value.

50. A method as defined in claim 49, wherein the prescribed fraction is approximately two-thirds.

51. A method as defined in claim 35, wherein the first controller is configured to initiate operation of the controllable impedance and the first controllable switch when the first controller detects that a voltage level of the main bus falls below a predetermined loss of bus detection value.

52. A method as defined in claim 35, wherein the first controller is configured controls the provision of a float current to the battery string in order to maintain a predetermined level of charge in the battery string.

53. A method as defined in claim 52, wherein the control of the float current delivered to the battery strings is at least partially based on temperature.