Method and apparatus for battery-power management using load-compensation monitoring of battery discharge

• US 5,027,294 A
• Filed: 01/27/1989
• Issued: 06/25/1991
• Est. Priority Date: 01/27/1989
• Status: Expired due to Term

• Current Assignee: NEC Corporation
• Original Assignee: Zenith Data Systems Corp. (Acer, Inc.)
• Inventors: Foster, Mark J., Fakruddin, Saifee
• Primary Examiner(s): Dixon, Joseph L.
• Application Number:
  US07/303,604
• Time in Patent Office: 879 Days
• Field of Search: 364/550, 364/551.01, 364/480, 364/481, 364/483, 364/200, 364/900, 324/426, 324/427, 324/429, 324/433, 324/434, 324/142, 340/636, 365/228, 365/229, 320/48
• US Class Current: 713/300
• 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: Y10S 320/21 State of charge of battery

Abstract

A method and apparatus for monitoring the voltage discharge of a battery power supply while under load, and to manage the power supply by accurately calculating the time the useful charge is nearly depleted, providing a series of warnings to the user-operator of that fact, and subsequently performing a system shutdown before a complete discharge of the battery. If the invention is applied to a battery power supply for a computer, the series of warnings enable the computer operator to transfer data from a temporary memory to permanent storage in the time interval between a warning signal and computer shutdown; and since computer shutdown is effected before the battery is fully discharged a battery-destructive phenomenon known as a polarity cell reversal is prevented. The battey monitoring and management techniques disclosed comprise generating periodically at a first rate a voltage-discharge value (SS) indicative of the rate of change of battery discharge voltage with respect to the elapse of time while the battery power supply is under load, generating periodically at the first rate a compensation-factor value (CF) which is numerically larger in absolute value than the absolute value of SS during at least the initial portion of the startup voltage depression and which is thereafter periodically decremented at a second rate until CF reaches a predetermined fixed value (FCF) approaching the SS of the stable section of the voltage discharge curve, and generating periodically at the first rate a real-time compensated voltage-discharge value (CSAV) in accordance with the functional expression: ##EQU1## The real-time CSAV(s) determine the particular battery management step taken.

Claims

1. Apparatus for managing a battery power supply connected to a load device using compensation for the rate of change of discharge voltage with respect to the elapse of time, comprising:

first means for generating a voltage-discharge value responsive to the rate of change of battery discharge voltage with respect to the elapse of time;

second means for generating a compensation-factor value which is generally numerically different from the voltage-discharge value;

third means for generating a compensated voltage-discharge value responsive to both the voltage-discharge value and the compensation-factor value; and

means responsive to said third generating means for initiating a shutdown of said load device under predetermined conditions.

2. Apparatus for managing a battery power supply connected to a load device using compensation for the rate of change of discharge voltage with respect to the elapse of time, comprising:

first means for generating a voltage-discharge value responsive to the rate of change of battery discharge voltage with respect to the elapse of time;

second means for generating a compensation-factor value which is generally numerically different from the voltage-discharge value;

third means for generating a compensated voltage-discharge value responsive to both the voltage-discharge value and the compensation-factor value wherein the battery power supply is characterized by normal voltage-discharge curve with the power supply fully charged having a startup voltage depression section under load, and in which the absolute value of the compensation-factor value during at least the initial portion of the startup voltage depression is numerically several times greater than the absolute value of the voltage-discharge value during the same period; and

means responsive to said third generating means for initiating a shutdown of said load device under predetermined conditions.

3. The apparatus of claim 2 in which the monitoring means is responsive during at least the initial portion of the startup voltage depression section to the numerical difference between the two absolute values.

4. The apparatus of claim 3 including means for decrementing the compensation-factor value during at least the initial portion of the startup voltage depression section.

5. The apparatus of claim 4 in which the compensation-factor value is periodically decremented to a predetermined fixed compensation-factor value with the time period separating successive steps of the decrementation being a fraction of the time period of the startup voltage depression section.

6. The apparatus of claim 5 in which the predetermined fixed compensation-factor value is equal to or approximately equal to the voltage-discharge value at a terminal portion of the startup voltage depression section.

7. The apparatus of claim 5 in which the voltage-discharge curve is further characterized by a stable voltage-discharge section following the startup voltage depression section, and in which the predetermined fixed compensation-factor value is approximately equal to the voltage-discharge value for at least the initial portion of the stable voltage section.

8. The apparatus of claim 5 in which the predetermined fixed compensation-factor value is slightly greater in absolute value than the absolute-value of the voltage-discharge value for at least the initial portion of the stable voltage section.

9. The apparatus of claim 4 for managing a battery power supply which may be subject to a voltage-discharge knee induced by an overcharge voltage depression, including timing means for generating a predetermined time period approximately equal to or greater than the length of time that a voltage discharge knee would persist due to an overcharge voltage depression.

10. The apparatus of claim 9 including means for detecting a predetermined timer-starting value which is a first function of the compensated voltage-discharge value occurring during an initial portion of the voltage-discharge knee induced by a overcharge voltage depression.

11. The apparatus of claim 10 in which the timing means is activated in response to the detection of the predetermined timer-starting value occurring during the voltage-discharge knee induced by an overcharge voltage depression.

12. The apparatus of claim 11 in which a second function of the compensated voltage-discharge value is detected at the end of the time period generated by the timing means.

13. The apparatus of claim 12 in which the voltage-discharge curve is further characterized by a rapidly-declining voltage-knee section terminating in complete battery discharge and following timewise the stable voltage section, and including means for effecting battery power management depending upon the second function of the voltage-discharge value measured at the end of the time period generated by the timing means.

14. The apparatus of claim 13 in which the means for effecting battery power management includes means selectively operable to issue a warning signal of low battery capacity characteristic of a voltage-discharge curve knee section terminating in complete battery discharge, to shutdown the load device, or to prevent the issuance of a warning signal and shutdown depending upon the numerical value of the second function of the compensated voltage-discharge value measured at the end of the time period generated by the timing means.

15. The apparatus of claim 14 including means for establishing a first predetermined threshold value for the second function of the compensated voltage-discharge value for issuing a warning signal and also a second predetermined threshold value for the second function of the compensated voltage-discharge value for shutting down the load device, and in which the selectively operable means returns the monitoring means to measuring compensated voltage-discharge values characterized by relatively constant voltage-discharge values if neither of the threshold values are exceeded at the end of the time period generated by the timing means.

16. The apparatus of claim 13 in which the means for effecting battery power management includes means selectively operable to issue at least two successive warning signals of low battery capacity characteristic of a voltage-discharge curve knee section terminating in complete battery discharge, to shutdown the load device, or to prevent the issuance of any warning signal and shutdown depending upon the particular numerical values for the second function of the compensated voltage-discharge values measured during a time period starting with and following the end of the time period generated by the timing means.

17. The apparatus of claim 16 in which each warning signal and shutdown is activated by different ranges of numerical values for the second function of the compensated voltage-discharge values with each range having a successively larger threshold value of activation.

18. The apparatus of claim 17 in which selectively operable means returns the monitoring means to measuring compensated voltage-discharge values characterized by relatively constant voltage-discharge values if none of the threshold values are exceeded at the end of the time period generated by the timing means.

19. Apparatus for monitoring a battery power supply, which has a normal voltage-discharge curve when connected to a load device, characterized by an initial startup voltage depression section, followed by a stable voltage section and ending with a rapidly declining voltage knee section terminating in loss of battery capacity, comprising:

first means for generating a voltage-discharge value (SS) responsive to the rate of change of battery discharge voltage with respect to the elapse of time while the battery power supply is under load;

second means for generating a compensation-factor value (CF) which is numerically different than the voltage-discharge value during at least the initial portion of the startup voltage depression section;

third means for generating a compensated voltage-discharge value (CSAV) is a function of the voltage-discharge factor (SS) and the compensation-factor value (CF) in accordance with the functional expression

space="preserve" listing-type="equation">CSAV=[(f)X]f(SS-CF)

during at least the initial portion of the startup voltage depression; and

means responsive to said third generating means for initiating a shutdown of said load device under predetermined conditions.

20. Apparatus for monitoring a battery power supply, which has a normal voltage-discharge curve when connected to a load device, characterized by an initial startup voltage depression section, followed by a stable voltage section and ending with a rapidly declining voltage knee section terminating in loss of battery capacity, comprising:

first means for generating a voltage-discharge value (SS) responsive to the rate of change of battery discharge voltage with respective to the elapse of time while the battery supply is under load;

second means for generating a compensation-factor value (CF) which is numerically different than the voltage-discharge value during at least the initial portion of the startup voltage depression section;

third means for generating a compensated voltage-discharge value (CSAV) as a function of the voltage-discharge factor (SS) and the compensation-factor (CF) in accordance with the functional expression

space="preserve" listing-type="equation">CSAV=[(f)X]f(SS-CF)

during at least the initial portion of the startup voltage depression wherein the absolute value of the initial CF at startup of battery discharge (start up compensation-factor (SCF)) is numerically greater than the absolute value of SS during the same time; and

means responsive to said third generating means for initiating a shutdown of said load device under predetermined conditions.

21. The apparatus of claim 20 in which the SCF is decremented periodically during the startup voltage depression section of a fully charged battery following a normal startup depression curve.

22. The apparatus of claim 21 in which the SCF is decremented until it reaches a predetermined fixed compensation value (FCF).

23. The apparatus of claim 22 in which the predetermined FCF is approximately equal to the SS of the terminal relatively-stable portion of the startup voltage depression section.

24. The apparatus of claim 22 in which the SCF is decremented to a FCF which approaches in value the SS of the voltage-discharge curve.

25. The apparatus of claim 22 in which the FCF is maintained at its fixed value throughout the stable voltage section of the voltage-discharge curve.

26. The apparatus of claim 25 in which the FCF is maintained at its fixed value throughout the rapidly-declining voltage knee section of the voltage-discharge curve.

27. Apparatus for monitoring and managing a battery power supply, which has normal voltage-discharge curve when fully charged and connected to a load device, characterized by an initial startup voltage depression section, followed by a stable voltage section, and ending with a rapidly declining voltage knee section terminating in loss of battery capacity, comprising:

first means for generating periodically at a first rate a voltage-discharge value (SS) indicative of the rate of change of battery discharge voltage with respect to the elapse of time while the battery power supply is under load;

second means for generating periodically at the first rate a compensation-factor value (CF) which is numerically larger in absolute value than the absolute value of SS during at least the initial portion of the startup voltage depression and is thereafter periodically decremented at a second rate until CF reaches a predetermined fixed value (FCF) approaching the SS of the stable section of the voltage-discharge curve;

third means for generating periodically at the first rate a real-time compensated voltage-discharge value (CSAV) as a function of the voltage-discharge factor (SS) and the compensation-factor (CF) in accordance with the functional expression ##EQU2## where SS is treated as a positive number for declining-voltage-discharge and as a negative number for increasing-voltage-discharge, where the previously taken quantity (SS-CF) is adjusted to a first fixed value if the

quantity is otherwise less than the first fixed value; and

means responsive to said third means for initiating a shutdown of said load device under predetermined conditions.

28. The apparatus of claim 27 including timing means for specifying a warning-signal time period, and means for activating the timing means in response to the real-time CSAV reaching a predetermined threshold value.

29. The apparatus of claim 28 including means for measuring the real-time CSAV at the end of the warning-signal time period.

30. The apparatus of claim 29 including means for triggering a warning signal (WL-1) in the event the real-time CSAV at the end of the warning-signal time period is equal to or greater than a predetermined WL-1 threshold value.

31. The apparatus of claim 30 including means for returning the monitoring and management means to measuring real-time CASV(s) characterized by relatively constant SS(s) in the event the WL-1 threshold value is not attained.

32. The apparatus of claim 29 including means for triggering a first warning signal (WL-1) in the event the real-time CSAV at the end of the warning-signal time period is within a first range of CSAV(s), and for triggering a second warning signal (WL-2) in the event the real-time CSAV at the end of the warning-signal time period is within a second and higher range of real-time CSAV(s).

33. The apparatus of claim 29 in which the triggering means also triggers a load device shutdown signal (SDV) in the event the real-time CSAV at the end of the warning-signal time period is within a third and still higher range of CSAV(s).

34. The apparatus of claim 32 in which the warning-signal time period is at least approximately equal to the time period of the declining voltage-discharge knee of an overcharge voltage depression.

35. The apparatus of claim 28 including means for selectively triggering a first warning signal (WL-1), a second warning signal (WL-2), a load-device shutdown signal, and a (SDV) in time progression in the event the real-time CSAV at the end of the warning-signal time period is equal to or greater than a predetermined WL-1 threshold value and thereafter the real-time CSAV progressively increases to equal or exceed a WL-2 threshold value and thereafter to equal or exceed a SDV threshold value.

36. The apparatus of claim 35 in which the selective triggering means returns the monitoring and management means to measure real-times CSAV'"'"'s characteristic of relatively stable SS(s) in the event the real-time CSAV measured at the end of the warning-signal time period fails to reach the WL-1 threshold value.

37. The apparatus of claim 35 in which the otherwise normal voltage-discharge curve of the battery power supply may be subjected to an overcharge voltage depression section characterized by a declining voltage-discharge knee followed by a period of relatively stable voltage discharge, and in which the timing means is activated in response to the real-time CSAV reaching the predetermined threshold value for activation in response to the power supply discharge passing through an overcharge voltage-discharge knee.

38. The apparatus of claim 37 in which the selective triggering means is deactivated at the end of the warning-signal time period in response to the measurement of a real-time CSAV less than the WL-1 threshold value.

39. The apparatus of claim 35 in which the otherwise normal discharge curve of a fully charged battery is abridged due to partial charging of the battery power supply with the result that the rapidly-declining voltage knee section terminating in loss of battery capacity is arrived at prematurely, including means for selectively reducing the number of times CF is periodically decremented thereby to start the warning counter time period earlier timewise than for a normal discharge curve.

40. Apparatus for monitoring and managing a battery power supply, which has a normal voltage-discharge curve when fully charged and connected to a load device, characterized by an initial startup voltage depression section, followed by a stable voltage section, and ending with a rapidly declining voltage knee section terminating in loss of battery capacity, comprising:

first means for generating periodically at a first rate a voltage-discharge value (SS) indicative of the rate of change of battery discharge voltage with respect to the elapse of time while the battery power supply is under load;

second means for generating periodically at the first rate a compensation-factor value (CF) which is numerically larger in absolute value than the absolute value of SS during at least the initial portion of the startup voltage depression and is thereafter periodically decremented at a second rate until CF reaches a predetermined fixed value (FCF) approaching the SS of the stable section of the voltage-discharge curve;

third means for generating periodically at the first rate a real-time compensated voltage-discharge value (CSAV) as a function of the voltage-discharge factor (SS) and the compensation-factor (CF) in accordance with the functional expression ##EQU3## where SS is treated as a positive number for declining-voltage-discharge and as a negative number for increasing-voltage-discharge, and where the previously taken quantity (SS-CF) is adjusted to a first fixed value if the quantity is otherwise less than the first fixed value

wherein the adjusted first fixed value is zero; and

means responsive to said third means for initiating a shutdown of said load device under predetermined conditions.

41. The method of managing a battery power supply connected to a load device which is energized by the battery power supply using compensation for the rate of change of discharge voltage with respect to a specified criteria, comprising:

generating a voltage-discharge value responsive to the rate of change of battery discharge voltage with respect to a specified criteria;

generating a compensation-factor value which is generally numerically different than the voltage-discharge value;

generating a compensated voltage-discharge value responsive to both the voltage-discharge value and the compensation-factor value for monitoring the battery discharge voltage; and

utilizing said compensated voltage-discharge value to initiate a shutdown of said load device under predetermined conditions.

42. The method of managing a battery power supply connected to a load device which is energized by the battery power supply using compensation for the rate of change of discharge voltage with respect to a specified criteria, comprising;

generating a voltage-discharge value responsive to the rate of change of battery discharge voltage with respect to a specified criteria;

generating a compensation-factor value which is generally numerically different than the voltage-discharge value;

generating a compensated voltage-discharge value responsive to both the voltage-discharge value and the compensation-factor value for monitoring the battery discharge voltage, wherein the battery power supply is characterized by a voltage-discharge curve having a startup voltage depression under load, and in which the absolute value of the compensation-factor value during at least the initial portion of the startup voltage depression is numerically several times greater than the absolute value of the voltage-discharge value during the same time period; and

utilizing said compensated voltage-discharge value to initiate a shutdown of said load device under predetermined conditions.

43. The method of claim 42 in which the monitoring step is responsive during at least the initial portion of the startup voltage depression to the numerical difference between the two absolute values.

44. The method of claim 43 including decrementing the compensation-factor value during at least the initial portion of the startup voltage depression.

45. The method of claim 44 in which the compensation-factor value is periodically decremented to a predetermined fixed value with the time period separating successive steps of the decrementation being a fraction of the time period of the startup voltage depression.

46. The method of claim 45 in which the predetermined fixed compensation-factor value is equal to or approximately equal to the voltage-discharge value at a terminal portion of the startup voltage depression section.

47. The method of claim 45 in which the voltage-discharge curve is further characterized by a stable voltage-discharge section following the startup voltage depression section, and in which the predetermined fixed compensation factor value is approximately equal to the voltage-discharge value for at least the initial portion of the stable voltage section.

48. The method of claim 45 in which the predetermined fixed compensation-factor value is slightly greater in absolute value than the absolute-value of the voltage-discharge value for at least the initial portion of the stable voltage section.

49. The method of claim 44 for managing a battery power supply which may be subject to a voltage-discharge knee induced by an overcharge voltage depression, including generating a predetermined time period approximately equal to or greater than the length of time that a voltage discharge knee would persist due to an overcharge voltage depression.

50. The method of claim 49 including detecting a predetermined compensated voltage discharge value occurring during an initial portion of the voltage-discharge knee induced by an overcharge voltage depression.

51. The method of claim 50 in which the generated time period is activated in response to the detection of the predetermined compensated voltage-discharge value occurring during the voltage-discharge knee induced by an overcharge voltage depression.

52. The method of claim 51 in which the compensated voltage-discharge value is measured at the end of the generated time period.

53. The method of claim 52 in which the voltage-discharge curve is further characterized by a rapidly-declining voltage knee section terminating in complete battery discharge and following timewise the stable voltage section, and effecting battery power management depending upon the voltage-discharge value measured at the end of the generated time period.

54. The method of claim 53 in which effecting battery power management includes selectively issuing a warning signal of low battery capacity characteristic of a voltage-discharge curve knee section terminating in complete battery discharge, shutting down the load device, or preventing the issuance of a warning signal and shutdown depending upon the numerical value of the second function of the compensated voltage-discharge value measured at the end of the generated time period.

55. The method of claim 54 including establishing a predetermined compensated voltage-discharge value for issuing a warning signal and also a predetermined compensated voltage-discharge threshold value for shutting down the load device, and in which compensated voltage-discharge values characterized by relatively constant voltage-discharge values are measured if neither of the threshold values are exceeded at the end of the generated time period.

56. The method of claim 53 includes operating selectively at least two successive warning signals of low battery capacity characteristic of a voltage-discharge curve knee section terminating in complete battery discharge, shutting down the load device, or preventing the issuance of any warning signal and shutdown depending upon the particular compensated voltage-discharge value measured at the end of the generated time period.

57. The method of claim 56 in which each warning signal and shutdown is activated by different ranges of compensated voltage-discharge values with each range having a successively larger threshold value of activation.

58. The method of claim 57 in which voltage-discharge values characterized by relatively constant voltage-discharge values are measured if none of the threshold values are exceeded at the end of the generated time period.

59. The method of monitoring a battery power supply connected to a load device which is energized by the battery power supply which has a voltage-discharge curve characterized by an initial startup voltage depression section, followed by a stable voltage section and ending with a rapidly declining voltage knee section terminating in loss of battery capacity, comprising:

generating a voltage-discharge value (SS) responsive to the rate of change of battery discharge voltage with respect to the elapse of time while the battery power supply is under load;

generating a compensation-factor value (CF) which is numerically different than the voltage-discharge value during at least the initial portion of the startup voltage depression;

generating a compensated voltage-discharge value (CSAV) as a function of the voltage-discharge value (SS) and the compensation-factor value (CF) in accordance with the functional expression

space="preserve" listing-type="equation">[SCAV]CSAV=[(f)x](SS-CF)

during at least the initial portion of the startup voltage depression; and

utilizing said compensated voltage-discharge value to initiate a shutdown of said load device under predetermined conditions.

60. The method of monitoring a battery power supply connected to a load device which is energized by the battery power supply which has a voltage-discharge curve characterized by an initial startup voltage depression section, followed by a stable voltage section and ending with a rapidly declining voltage knee section terminating in loss of battery capacity, comprising;

generating a voltage-discharge value (SS) responsive to the rate of change of battery discharge voltage with respect to the elapse of time while the battery power supply is under load;

generating a compensation-factor value (CF) which is numerically different than the voltage-discharge value during at least the initial portion of the startup voltage depression;

generating a compensated voltage-discharge value (CSAV) as a function of the voltage-discharge value (SS) and the compensation (CF) in accordance with the functional expression

space="preserve" listing-type="equation">[SCAV]CSAV=[(f)X]f(SS-CF)

during at least the initial portion of the startup voltage depression wherein the absolute value of the initial CF at startup of battery discharge (startup compensation factor (SCF)) is numerically greater than the absolute value of SS during the same time; and

utilizing said compensated voltage-discharge value (CSAV) to initiate a shutdown of said load device under predetermined conditions.

61. The method of claim 60 in which the SCF is decremented periodically during the startup voltage depression section of a fully charged battery following a normal startup depression curve.

62. The method of claim 61 in which the SCF is decremented until it reaches a predetermined fixed compensation value (FCF).

63. The method of claim 62 in which the predetermined FCF is approximately equal to the SS of the terminal and relatively stable portion of the startup voltage depression section.

64. The method of claim 62 in which the SCF is decremented to a FCF which approaches in value the SS of the voltage-discharge curve.

65. The method of claim 62 in which the FCF is maintained at its fixed value throughout the stable voltage section of the voltage-discharge curve.

66. The method of claim 65 in which the FCF is maintained at its fixed value throughout the rapidly-declining voltage knee section of the voltage-discharge curve.

67. The method of monitoring and managing a battery power supply, which has a normal voltage-discharge curve when fully charged and connected to a load device, characterized by an initial startup voltage depression section, followed by a stable voltage section and ending with a rapidly declining voltage knee section terminating in loss of battery capacity, comprising:

generating periodically at a first rate a voltage-discharge value (SS) indicative of the rate of change of battery discharge voltage with respect to the elapse of time while the battery power supply is under load;

generating periodically at the first rate a compensation-factor value (CF) which is numerically larger in absolute value than the absolute value of SS during at least the initial portion of the startup voltage depression and which is thereafter periodically decremented at a second rate until CF reaches a predetermined fixed value (FCF) approaching the SS of the stable section of the voltage-discharge curve;

generating periodically at the first rate a real-time compensated voltage-discharge value (CSAV) as a function of the voltage-discharge value (SS) and the compensation-factor (CF) in accordance with the functional expression ##EQU4## where SS is treated as a positive number for declining-voltage-discharge and as a negative number for increasing-voltage-discharge, and where the previously taken quantity (SS-CF) is adjusted to a first fixed value if the quantity is otherwise less than the first fixed value numerically; and

utilizing said compensated voltage-discharge value (CSAV) to initiate a shutdown of said load device under predetermined conditions.