Battery monitor and method for providing operating parameters

• US 5,321,627 A
• Filed: 03/11/1992
• Issued: 06/14/1994
• Est. Priority Date: 03/11/1992
• Status: Expired due to Term

• Current Assignee: C&D Technologies Incorporated (Angel Holdings LLC)
• Original Assignee: Globe-Union Inc.
• Inventors: Reher, Michael T.
• Primary Examiner(s): Black, Thomas G.
• Assistant Examiner(s): ZANELLI, MICHAEL J
• Application Number:
  US07/850,405
• Time in Patent Office: 825 Days
• Field of Search: 364/550, 364/551.01, 364/481, 364/483, 364/557, 324/426, 324/427, 324/428, 324/431, 340/636, 320/48, 320/43
• US Class Current: 702/63
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/374 with means for correcting the measurement for temperature or ageing
• CPC Class Codes: G01R 31/379 for lead-acid batteries
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• CPC Class Codes: H01M 10/48 Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals, H01M50/569
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y10S 320/21 State of charge of battery

Abstract

A battery monitor which monitors the operating parameters of a battery to provide an indication of, for example, the absolute state of charge, the relative state of charge, and the capacity of the battery under battery discharge, rest, and recharge conditions. The battery monitor includes a current sensor for sensing battery current, a voltage sensor for sensing battery voltage, and a temperature sensor for sensing battery temperature. A processor approximates to a high level of accuracy the battery parameters utilizing an iterative process based upon predetermined relationships, employing empirically determined constants and parameters determined in the immediately proceeding iteration stored in memory. Output signals indicative of the determined parameters are provided and may be utilized for many different battery applications.

Claims

1. A battery monitor for monitoring operating parameters of a battery, said battery monitor comprising:

voltage sensor means for sensing batter voltage and providing a voltage sensor signal indicative of said battery voltage;

current sensor means for sensing battery current and providing a current sensor signal indicative of said battery current;

processing means coupled to said voltage sensor means and said current sensor means for reading said voltage sensor signal, for reading said current sensor signal, and for computing said operating parameters at spaced apart computing times;

memory means coupled to said processing means for storing selected ones of the last computed said operating parameters;

said processing means determining when said battery is in discharge and computing, responsive to said voltage sensor signal and said current sensor signal, a corrected battery voltage and, from said corrected battery voltage, computing relative state of charge of said battery, said processing means computing a factor representing the difference between absolute state of charge of said battery and sad relative state of charge of said battery, said processing means computing said absolute state of charge of said battery from a sum of said relative state of charge of said battery and said factor; and

output means coupled to said processing means for providing output signals indicative of predetermined ones of said operating parameters.

2. A battery monitor as defined in claim 1 further including temperature sensing means for sensing the battery temperature and providing said processing means with a temperature sensor signal indicative of said battery temperature and wherein said processing means computes said corrected battery voltage responsive to said temperature sensor signal.

3. A battery monitor as defined in claim 1 wherein said processing means computes the rated capacity of said battery and the current capacity of said battery.

4. A battery monitor as defined in claim 3 wherein said processing means further stores the last read said current sensor signal and the last computed said factor of said battery in said memory means.

5. A battery monitor as defined in claim 4 wherein said processing means computes said factor based upon said rated capacity of said battery, said current capacity of said battery, said stored last computed factor of said battery, the time since the last said computing time, and said stored last read current sensor signal.

6. A battery monitor as defined in claim 3 wherein said processing means further computes the capacity of said battery and stores said capacity of said battery in said memory means.

7. A battery monitor as defined in claim 6 wherein said processing means computes said rated capacity of said battery based upon said stored capacity and computes said current capacity of said battery based upon said stored capacity and said current sensor signal.

8. A battery monitor as defined in claim 6 wherein said processing means computes the integrated amp hour state of charge of said battery and computes said capacity of said battery based upon said stored capacity, said absolute state of charge of said battery, said integrated amp-hour state of charge of said battery and the time since the last said computing time.

9. A battery monitor as defined in claim 3 further including temperature sensing means for sensing the battery temperature and providing said processing means with a temperature sensor signal indicative of said battery temperature and wherein said processing means is further responsive to said temperature sensor signal for computing a temperature compensation value for computing said rated capacity of said battery and said current capacity of said battery.

10. A battery monitor as defined in claim 1 wherein said processing means stores said absolute state of charge of said battery and said factor in said memory means.

11. A battery monitor as defined in claim 10 wherein said processing means limits the value of said computed absolute state of charge of said battery and stores said limited absolute state of charge value of said battery in said memory means.

12. A battery monitor as defined in claim 11 wherein said processing means further computes the state of charge used by said battery since the last s id computing time.

13. A battery monitor as defined in claim 12 wherein said processing means limits the value of said computed absolute state of charge of said battery between the difference between the last stored said limited absolute state of charge value and the quantity of a first constant times said state of charge used by said battery and the difference between the last stored said limited absolute state of charge value and the quantity of a second constant times the said state of charge used by said battery.

14. A battery monitor as defined i claim 1 wherein said processing means limits the value of said computed relative state of charge of said battery and stores said limited relative state of charge value of said battery in said memory means.

15. A battery monitor as defined in claim 14 wherein said processing means further computes the state of charge used by said battery since the last said computing time.

16. A battery monitor as defined in claim 15 wherein said processing means limits the value of said computed relative state of charge of said battery between the difference between the last stored said limited relative state of charge value and the quantity of a first constant times the said state of charge used by said battery and the difference between the last stored said limited relative state of charge value and the quantity of a second constant times the said state of charge used by said battery.

17. A battery monitor as defined in claim 1 wherein said processing means computes at each of said computing times the relative state of charge of said battery and wherein said output signals include an output signal indicative of said relative state of charge of said battery.

18. A battery monitor as defined in claim 1 wherein said processing means computes at each of said computing times the absolute state of charge of said battery and wherein said output signals include an output signal indicative of said absolute state of charge of said battery.

19. A battery monitor as defined in claim 1 wherein said processing means computes at each of said computing times the fully charged output capacity of said battery at a given discharge current and wherein said output signals include an output signal indicative of said fully charged output capacity of said battery at said given discharge current.

20. A battery monitor as defined in claim 1 wherein said processing means computes at each of said computing times the remaining output capacity of said battery at a given discharge current and wherein said output signals include an output signal indicative of said remaining output capacity.

21. A battery monitor as defined in claim 1 wherein said processing means computes at each of said computing times the time to empty of said battery representing the time in which said battery will be fully discharged at a given discharge current and wherein said output signals include an output signal indicative of said time to empty.

22. A battery monitor as defined in claim 1 wherein said processing means computes at each of said computing times the required amp-hours to fully recharge said battery and wherein said output signals include an output signal indicative of said amp-hours to fully recharge said battery.

23. A battery monitor as defined in claim 1 wherein said processing means computes at each of said computing times the time to fully recharge said battery at a given recharge current and wherein said output signals include an output signal indicative of said time to fully recharge said battery.

24. A battery monitor as defined in claim 1 wherein said processing means computes at each of said computing times a recommended recharge voltage for recharging said battery and wherein said output signals include an output signal indicative of said recommended recharge voltage.

25. A battery monitor as defined in claim 1 wherein said processing means at each of said computing times computes a critical restart temperature of said battery and wherein said output signals include an output signal indicative of said critical restart temperature of said battery.

26. A battery monitor for monitoring operating parameters of a battery, said battery monitor comprising:

voltage sensor means for sensing battery voltage and providing a voltage sensor signal indicative of said battery voltage;

current sensor means for sensing battery current and providing a current sensor signal indicative of said battery current;

processing means coupled to said voltage sensor means and said current sensor means for reading said voltage sensor signal, for reading said current sensor signal, and for computing said operating parameters at spaced apart computing times;

memory means coupled to said processing means for storing selected one of the last computed said operating parameters;

said processing means determining when said battery is at rest and computing, responsive to said voltage sensor signal and said current sensor signal, an open circuit voltage of said battery and from said open circuit voltage, computing an open circuit voltage state of charge of said battery, said processing means determining if said open circuit voltage is accurate and setting absolute state of charge of said battery equal to said open circuit state of charge of said battery when said processing means determines that said open circuit voltage state of charge is accurate; and

output means coupled to said processing means for providing output signals indicative of predetermined ones of said operating parameters.

27. A battery monitor as defined in claim 26 further including timing means for determining the time in which said battery is at rest.

28. A battery monitor as defined in claim 27 wherein said processing means resets said timing means when said battery is not at rest.

29. A battery monitor as defined in claim 27 wherein said processing means is further responsive to said current sensor signal for determining if said battery is at rest or not at rest.

30. A batter monitor as defined in claim 29 wherein, when said battery is not at rest, said processing means resets the said time in which said battery is at rest.

31. A battery monitor as defined in claim 29 wherein said processing means increments said timing means with the time since the last said computing time when said battery is at rest.

32. A battery monitor as defined in claim 27 wherein said processing means determines if said battery has been at rest for a period of time greater than a first time period and determines that said open circuit voltage state of charge is accurate when said battery has been at rest for a period of time greater than said first time period.

33. A battery monitor as defined in claim 27 wherein said processing means determines if said battery has been at rest for an intermediate time period greater than a second time period but less than a first time period.

34. A battery monitor as defined in claim 33 wherein said processing means computes the absolute state of charge of said battery prior to determining if said battery has been at rest for said intermediate time period.

35. A battery monitor as defined in claim 34 wherein said processing means also computes the relative state of charge of said battery responsive to said absolute state of charge of said battery and a last computed factor stored in said memory means, wherein said factor represents the difference between said absolute state of charge of said battery and said relative state of charge of said battery.

36. A battery monitor as defined in claim 34 wherein said processing means determines, when said battery has been at rest for said intermediate time period, if the difference between said open circuit voltage state of charge and the absolute state of charge of said battery is less than a given magnitude and determines that said open circuit voltage state of charge is accurate when said difference is less than said given magnitude.

37. A battery monitor as defined in claim 36 wherein said processing means advances said timing means to said first time period upon determining that said open circuit voltage state of charge is accurate.

38. A battery monitor as defined in claim 34 wherein said processing means determines a given range of values such that the magnitude of the difference between said given range of values and said absolute state of charge of said battery is less than a constant.

39. A battery monitor as defined in claim 38 wherein said processing means computes said given range of values responsive to the time since the last computing time and the time since said battery was last not at rest.

40. A battery monitor as defined in claim 38 wherein, when said battery has been at rest for said intermediate time period, said processing means sets said absolute state of charge of said battery equal to said open circuit voltage state of charge of said battery and adjusts said absolute state of charge of sid battery to within said given range of values if sid open circuit voltage state of charge of said battery is outside of said given range of values.

41. A battery monitor as defined in claim 26 further including temperature sensing means for sensing the battery temperature and providing said processing means with a temperature sensing signal indicative of said battery temperature, and wherein said processing means is further responsive to said temperature sensor signal for computing said open circuit voltage of said battery.

42. A battery monitor as defined in claim 26 wherein said processing means further computes the integrated amp-hour state of charge of said battery, the capacity of said battery and stores the last computed said capacity of said battery and the last state of charge value.

43. A battery monitor as defined in claim 42 wherein said processing means determines if the difference between said last state of charge value and said absolute state of charge is greater than a given amount and computes said capacity responsive to the last computed capacity, said absolute state of charge, said last state of charge value, and said integrated amp-hour state of charge of said battery when said difference between said last state of charge value and said absolute state of charge is greater than said given amount.

44. A battery monitor for monitoring operating parameters of a battery, said battery monitor comprising:

voltage sensor means for sensing batter voltage and providing a voltage sensor signal indicative of said battery voltage;

current sensor means for sensing battery current and providing a current sensor signal indicative of said battery current;

processing means coupled to said voltage sensor means and said current sensor means for reading said voltage sensor signal, for reading said current sensor signal, and for computing said operating parameters at spaced apart computing times;

memory means coupled to said processing means for storing selected ones of the last computed said operating parameters;

said processing means determining in response to said current sensor signal if said battery is in recharge, said processing means determining state of charge added to said battery since the last said computing time, said processing means computing at each of said computing times and storing in said memory means absolute state of charge of said batter, said processing means computing at each of said computing times and storing in said memory means a factor representing the difference between said absolute state of charge of said battery and relative state of charge of said battery; and

output means coupled to said processing means for providing output signals indicative of predetermined ones of said operating parameters.

45. A battery monitor as defined in claim 44 wherein said processing means computes said factor by determining, when said battery is in recharge, the difference between the last said factor stored in said memory means and the state of charge added to said battery.

46. A battery monitor as defined in claim 44 wherein said processing means further computes the relative state of charge of said battery responsive to said absolute state of charge of said battery and the last computed factor stored in said memory means.

47. A battery monitor as defined in claim 44 wherein, when said battery is in recharge, said processing means computes the gassing current of said battery representing the amount of recharge current which is not being used to recharge said battery.

48. A battery monitor as defined in claim 47 wherein said processing means computes said gassing current responsive to said voltage sensor signal.

49. A battery monitor as defined in claim 48 further including temperature sensing means for sensing the battery temperature and providing said processing means with a temperature sensor signal indicative of said battery temperature and wherein said processing means computes said gassing current responsive to said temperature sensor signal.

50. A battery monitor as defined in claim 47 wherein said memory means stores the last read said current sensor signal and, wherein said processing means determines if said last current sensor signal stored in said memory means is greater than said gassing current and computes an adjusted state of charge added to said battery since the last said computing time when said last current sensor signal stored in said memory means is greater than said gassing current.

51. A battery monitor as defined in claim 50 wherein said processing means computes the rated capacity of said battery and wherein said adjusted state of charge added to said battery is equal to the time since said last computing time multiplied by the difference between said last current and said gassing current divided by said rated capacity of said battery.

52. A battery monitor as defined in claim 44 wherein said processing means, when said battery is i recharge, further computes and stores in said memory means an integrated amp-hour state of charge of said battery by summing the last integrated amp-our state of charge of said battery stored in said memory means and said state of charge added to said battery.

53. A battery monitor as defined in claim 44 wherein said processing means computes said absolute state of charge of said battery, when said battery is in recharge, by summing the last said absolute state of charge of said battery stored in said memory means and said state of charge added to said battery

54. A battery monitor as defined in claim 53 wherein said processing means, when said battery is in recharge, computes said factor by determining the difference between the last said factor stored in said memory means and said state of charge added to aid battery.

55. A battery monitor as defined in claim 54 wherein said processing means computes said relative state of charge of said battery by determining the difference between said absolute state of charge of said battery and said factor.

56. A method of monitoring the operating parameters of a battery, said method comprising the steps of:

providing a voltage sensor;

sensing battery voltage and providing a voltage sensor signal indicative of said battery voltage;

providing a current sensor;

sensing battery current and providing a current sensor signal indicative of said battery current;

providing processing means coupled to said voltage sensor and said current sensor for reading said voltage sensor signal, for reading said current sensor signal, and for computing said operating parameters at spaced apart computing times;

providing memory means coupled to said processing means;

storing selected ones of the last computed said operating parameters in said memory means;

computing, when said battery is in discharge, responsive to said voltage sensor signal and said current sensor signal, a corrected battery voltage and computing from said corrected battery voltage relative state of charge of said battery;

computing a factor representing the difference between absolute state of charge of said battery ad said relative state of charge of sid battery and computing said absolute state of charge of said battery from a sum of said relative state of charge of said battery and said factor; and

providing output signals indicative of predetermined ones of said operating parameters

57. A method as defined in claim 56 comprising the further steps of providing a temperature sensor, sensing the battery temperature and providing said processing means with a temperature sensor signal indicative of said battery temperature, and computing said corrected battery voltage responsive to said temperature sensor signal.

58. A method as defined in claim 56 comprising the further steps of computing the rated capacity of said battery and the current capacity of said battery.

59. A method as defined in claim 58 comprising the further steps of storing the last read said current sensor signal and the last computed said factor of said battery in said memory means.

60. A method as defined in claim 59 comprising the further steps of computing said factor based upon said rated capacity of said battery, said current capacity of said battery, said stored last computed factor of said battery, the time since the last said computing time, and said stored last read current sensor signal.

61. A method as defined in claim 58 comprising the further steps of computing the capacity of said battery and storing said capacity of said battery in said memory means.

62. A method as defined in claim 61 comprising the further steps of computing said rated capacity of said battery based upon said stored capacity and computing said current capacity of said battery based upon said stored capacity and said current sensor signal.

63. A method as defined in claim 61 comprising the further steps of computing the integrated amp-hour state of charge of said battery and computing said capacity of said battery based upon said stored capacity, said absolute state of charge of said battery, said integrated amp-hour state of charge of said battery and the time since the last said computing time.

64. A method as defined in claim 58 comprising the further steps of providing a temperature sensor, sensing the battery temperature and providing said processing means with a temperature sensor signal indicative of said batter temperature and computing, responsive to said temperature sensor signal, a temperature compensation value for computing said rated capacity of said battery and said current capacity of said battery.

65. A method as defined in claim 56 comprising the further steps of storing said absolute state of charge of said battery and said factor in said memory means.

66. A method as defined in claim 65 comprising the further steps of limiting the value of said computed absolute state of charge of said battery and storing said limited absolute state of charge of said battery in said memory means.

67. A method as defined in claim 66 comprising the further steps of computing the step of charge used by said battery since the last said computing time.

68. A method as defined in claim 67 comprising the further steps of computing said limited absolute state of charge of said battery between the difference between the last stored said limited absolute state of charge value and the quantity of a first constant times the said state of charge used by said battery and the difference between the last stored said limited absolute state of charge value and the quantity of a second constant times the said state of charge used b y said battery.

69. A method as defined in claim 56 comprising the further steps of limiting the value of said computed relative state of charge of said battery and storing said limited relative state of charge value of said battery in said memory means.

70. A method as defined in claim 69 comprising the further steps of computing the state of charge used by said battery since the last said computing time.

71. A method as defined in claim 70 comprising the further steps of computing said computed limited relative state of charge of said battery between the difference between the last stored said limited relative state of charge value ad the quantity of a first constant times the said state of charge used by said battery and the difference between the last stored said limited relative state of charge value and the quantity of a second constant times the said state of charge used by said battery.

72. A method as defined in claim 56 comprising the further steps of computing at each of said computing times the relative state of charge of sid battery and providing an output signal indicative of said relative state of charge of said battery.

73. A method as defined in claim 56 comprising the further steps of computing at each of said computing times the absolute state of charge of said battery and providing an output signal indicative of the said absolute state of charge of said battery.

74. A method as defined in claim 56 comprising the further steps of computing at each of said computing times the fully charged output capacity of said battery at a given discharge current and providing an output signal indicative of said fully charged output capacity of said battery at said given discharge current.

75. A method as defined in claim 56 comprising the further steps of computing at each of said computing times the remaining output capacity of said battery at a given discharge current and providing an output signal indicative of said remaining output capacity.

76. A method as defined in claim 56 comprising the further steps of computing at each of said computing times the time to empty of said battery representing the time in which said battery will be fully discharged at a given discharge current and providing an output signal indicative of said time to empty.

77. A method as defined in claim 56 comprising the further steps of computing at each of said computing times the required amp-hours to fully recharge said battery and providing an output signal indicative of said amp-hours to fully recharge said battery.

78. A method as defined in claim 56 comprising the further steps of computing at each of said computing times the time to fully recharge said battery at a given recharge current and providing an output signal indicative of said time to fully recharge said battery.

79. A method as defined in claim 56 comprising the further steps of computing at each of said computing times a recommended recharge voltage for recharging said battery and providing an output signal indicative of said recommended recharge voltage.

80. A method as defined in claim 56 comprising the further steps of computing at each of said computing times a critical restart temperature of said battery and providing an output signal indicative of said critical restart temperature of said battery.

81. A method of monitoring the operating parameters of a battery, said method comprising the steps of:

providing a voltage sensor;

sensing battery voltage and providing a voltage sensor signal indicative of said battery voltage;

providing a current sensor;

sensing battery current and providing a current sensor signal indicative of said battery current;

providing processing means coupled to said voltage sensor and said current sensor for reading said voltage sensor signal, for reading said current sensor signal, and for computing said operating parameters at spaced apart computing times;

providing memory means coupled to sid processing means;

storing selected ones of the last computed said operating parameters in said memory means;

computing, when sid battery is at rest, responsive to said voltage sensor signal and said current sensor signal, the open circuit voltage and computing from said open circuit voltage the open circuit voltage state of charge of said battery;

determining if said open circuit voltage state of charge is accurate and setting absolute state of charge of said battery equal to the open circuit voltage state of charge of said battery after determining that said open circuit voltage state of charge is accurate; and

providing output signals indicative of predetermined ones of said operating parameters.

82. A method as defined in claim 81 comprising the further steps of providing timing means for determining the time in which said battery is at rest.

83. A method as defined in claim 82 comprising the further steps of resetting said timing means when said battery is not at rest.

84. A method as defined in claim 82 comprising the further steps of determining if said battery is at rest or not at rest responsive to said current sensor signal.

85. A method as defined in claim 84 comprising the further steps of, when said battery is not at rest, resetting said tie in which said battery is at rest.

86. A method as defined in claim 84 comprising the further steps of incrementing said timing means with the time since the last said computing time when said battery is at rest.

87. A method as defined in claim 82 comprising the further steps of determining if said battery has been at rest for a period of time greater than a first time period and determining that said open circuit voltage state of charge is accurate when said battery has been at rest for a period of time greater than said first time period.

88. A method as defined in claim 82 comprising the further steps of determining if said battery has been at rest for an intermediate time period greater than a second time period but less than a first time period.

89. A method as defined in claim 88 comprising the further steps of computing the absolute state of charge of said battery prior to determining if said battery has been at rest for said intermediate time period.

90. A method as defined in claim 89 comprising the further steps of computing the relative state of charge of said battery responsive to said absolute state o charge of said battery and the last computed factor stored in said memory means, wherein said factor represents the difference between said absolute state of charge of said battery and said relative state of charge of said battery.

91. A method as defined in claim 89 comprising the further steps determining, when said battery has been at rest for said intermediate time period, if the difference between said open circuit voltage state of charge and the absolute state of charge of said battery is less than a given magnitude and determining that said open circuit voltage state of charge is accurate when said difference is less than said given magnitude.

92. A method as defined in claim 91 comprising the further steps of advancing said timing mans to said first time period upon determining that said open circuit voltage state of charge is accurate.

93. A method as defined in claim 89 comprising the further steps of determining a given range of values wherein the difference between said given range of values and said absolute state of charge of said battery is less than a constant.

94. A method as defined in claim 93 comprising the further steps of computing said given range of values responsive to the time since the last computing time and the time since said battery was last not at rest.

95. A method as defined in claim 93 comprising the further steps of, when said battery has been at rest for said intermediate time period, setting said absolute state of charge of said battery equal to said open circuit voltage state of charge of said battery and adjusting said absolute state of charge of said battery to within said given range if said open circuit voltage state of charge of sid battery is outside of said given range.

96. A method as defined in claim 81 comprising the further steps of providing a temperature sensor, sensing the battery temperature and providing said processing means with a temperature sensing signal indicative of said batter temperature, and computing, responsive to said temperature sensor signal, said open circuit voltage of said battery.

97. A method as defined in claim 81 comprising the further steps of causing said processing means to compute the integrated amp-hour state of charge of said battery, to compute the capacity of said battery and to store the last computed said capacity of said battery and the last state of charge value.

98. A method as defined in claim 97 comprising the further steps of determining if the difference between said last state of charge value and said absolute state of charge is greater than a given amount and computing said capacity responsive to the last computed capacity, said absolute state of charge, said last state of charge value, and said integrated amp-hour state of charge of sid battery when said difference between said last state of charge value and said absolute state of charge is greater than said given amount.

99. A method of monitoring the operating parameters of a battery, sid method comprising the steps of:

providing a voltage sensor;

sensing battery voltage and providing a voltage sensor signal indicative of said battery voltage;

providing a current sensor;

sensing battery current and providing a current sensor signal indicative of said battery current;

providing processing means coupled to said voltage sensor and said current sensor for reading said voltage sensor signal, for reading said current sensor signal, and for computing said operating parameters at spaced apart computing times;

providing memory means coupled to said processing means;

storing selected ones of the last computed said operating parameters in said memory means;

determining, when said battery is in recharge, the state of charge added to said battery since the last said computing time, and computing at each of said computing times and storing in said memory means the absolute state of charge of said battery;

computing at each of said computing times and storing in said memory means a factor representing the difference between said absolute state of charge of said battery and relative state of charge of said battery; and

providing output signals indicative of predetermined ones of said operating parameters.

100. A method as defined in claim 99 comprising the further steps of computing said factor by determining, when said battery is in recharge, the difference between the last said factor stored in said memory means and the state of charge added to said battery.

101. A method as defined in claim 99 comprising the further steps of computing said relative state of charge of said battery responsive to sid absolute state of charge of said battery and the last computed factor stored in said memory means.

102. A method as defined in claim 99 comprising the further steps of computing, when said battery is in recharge, the gassing current of said battery representing the amount of recharge current which is not being used to recharge said battery.

103. A method as defined in claim 102 comprising the further steps of computing said gassing current responsive to said voltage sensor signal.

104. A method as defined in claim 103 comprising the further steps of providing a temperature sensor, sensing the battery temperature and providing said processing means with a temperature sensor signal indicative of said battery temperature and computing said gassing current responsive to said temperature sensor signal.

105. A method as defined in claim 102 comprising the further steps of storing in said memory means the last read said current sensor signal and determining if said last current sensor signal stored in said memory means is greater than said gassing current and computing an adjusted state of charge added to said battery since the last said computing time when said last current sensor signal stored in said memory means is greater than said gassing current.

106. A method as defined in claim 105 comprising the further steps of computing the rated capacity of said battery and wherein said adjusted state of charge added to said battery is equal to the time since said last computing time multiplied by the difference between said last current sensor signal and said gassing current divided by said rated capacity of said battery.

107. A method as defined in claim 99 comprising the further steps of, when sid battery is in recharge, computing and storing in said memory means the integrated amp-hour state of charge of sid battery by summing the last said integrated amp-hour state of charge of said battery stored in said memory means and said state of charge added to said battery.

108. A method as defined in claim 99 comprising the further steps of computing, when said battery is in recharge, said absolute state of charge of said battery by summing the last said absolute state of charge of said battery stored in said memory means and said state of charge added to said battery.

109. A method as defined in claim 108 comprising the further steps of computing, when said battery is in recharge, said factor by determining the difference between the last said factor stored in said memory means and said state of charge added to said battery.

110. A method as defined in claim 109 comprising the further steps of computing said relative state of charge of said battery by determining the difference between the said absolute state of charge of said battery and said factor.

111. A battery monitor for use with a batter, said battery monitor comprising:

processing means;

voltage sensor means coupled to said processing means for sensing battery voltage and providing a voltage sensor signal to said processing means;

current sensor means coupled to said processing means or sensing battery current and providing a current sensor signal to said processing means;

said processing means computing;

(1) the rated capacity of said battery;

(2) the current capacity of said battery;

(3) the state of charge used by said battery;

(4) a factor of said battery;

(5) the absolute state of charge of said battery; and

(6) the relative state of charge of said battery; and

output means coupled to sadi processing means for providing output signals including a signal indicative of said absolute state of charge of said battery.

112. A battery monitor as defined in claim 111 wherein said output signals include a signal indicative of said relative state of charge of said battery.

113. A battery monitor as defined in claim 111 further comprising temperature sensing means for sensing battery temperature and providing a temperature sensor signal to said processing means.

114. A battery monitor as defined in claim 111 wherein said processing means includes timing means for causing said processor to calculate said rated capacity of said battery;

said current capacity of said battery;

said state of charge used by said battery;

said factor of said battery;

said absolute state of charge of said battery; and

said relative state of charge of said battery at spaced apart time intervals.

115. A battery monitor as defined in claim 111 further comprising timing means for sensing elapsed time and providing a timing signal to said processing means.

116. A battery monitor as defined in claim 111 wherein said processing means include storing means for storing the last computed said factor of said battery and the last computed said absolute state of charge of said battery.

117. A battery monitor as defined in claim 116 wherein said processing means determines whether said battery is in a recharge state or a discharge state responsive to said current sensor signal.

118. A battery monitor as defined in claim 117 wherein said processing means computes said absolute state of charge of said battery when said battery is in said recharge state by subtracting said state of charge used by said battery from said last computed absolute state of charge of said battery.

119. A battery monitor as defined in claim 118 wherein said processing means computes said state of charge used by said battery when said battery is in said recharge state by multiplying the difference between a gassing current, derived from said voltage sensor signal, and said current sensor signal, by the time since the last said computing time, and dividing by said rated capacity of said battery.

120. A battery monitor as defined in claim 119 wherein said processing means computes said absolute state of charge of said battery when said battery is in said recharge state by subtracting said state of charge used by said battery from said last computed absolute state of charge of said battery.

121. A battery monitor as defined in claim 120 wherein said processing means computes said relative state of charge of said battery when said battery is in said recharge state by subtracting said factor from said absolute state of charge of said battery, said factor being determined from said last computed factor and said state of charge used by said battery.

122. A battery monitor as defined in claim 118 wherein said processing means computes said relative state of charge of said battery when said battery is in said recharge state by subtracting said factor of said battery from said absolute state of charge of said battery, said factor of said battery being determined from:

said last computed factor of said battery and the state of charge used by said battery.

123. A battery monitor as defined in claim 117 wherein said processing means computes said relative state of charge of said battery when said battery is in said discharge state responsive to said voltage sensor signal and said current sensor signal.

124. A battery monitor as defined in claim 123 wherein said processing means computes said absolute state of charge of said battery when said battery is in said discharge state by adding said factor of said battery to said relative state of charge of said battery, said factor being determined from:

said rated capacity of said battery;

said current capacity of said battery;

said current sensor signal;

said last computed factor; and

said state of charge used by said battery.

125. A battery monitor as defined in claim 124 wherein said processing means limits the computed values for said relative state of charge and said absolute state of charge responsive to said last computed stored absolute state of charge of said battery, said factor of said battery, and said state of charge used by said battery and a constant.

126. A method of monitoring the absolute state of charge of a storage battery, said method comprising the steps of:

providing processing means;

providing voltage sensor means coupled to said processing means;

sensing the voltage of said battery and providing a voltage sensor signal to said processing means;

providing current sensor means coupled to said processing means;

sensing the battery current and providing a current sensor signal to said processing means;

computing by said processing means;

(1) the rated capacity of said battery;

(2) the current capacity of said battery;

(3) the state of charge used by said batter;

(4) a factor of said battery;

(5) the absolute state of charge of said battery; and

(6) the relative state of charge of said battery; and

providing an output signal indicative of said absolute state of charge of said battery.

127. A method as defined in claim 126 further comprising the step of providing an output signal indicative of said relative state of charge of said battery.

128. A method as defined in claim 126 further comprising the steps of providing temperature sensing means for sensing battery temperature and providing a temperature sensor signal to said processing means.

129. A method as defined in claim 126 further comprising the steps of calculating said rated capacity of said battery;

said current capacity of said battery;

said state of charge used by said battery;

said factor of said battery;

said absolute state of charge of said battery; and

said relative state of charge of said battery at spaced apart time intervals.

130. A method as defined in claim 129 including the further step of storing the last computed said factor of said battery and the last computed said absolute state of charge of said battery.

131. A method as defined in claim 130 including the further step of determining whether said battery is in a recharge state or a discharge state responsive to said current sensor signal.

132. A method as defined in claim 131 including the further step of computing said absolute state of charge of said battery when said battery is in said recharge state by subtracting said state of charge used by said battery from said last computed absolute state of charge of said battery.

133. A method as defined in claim 132 including the further step of computing said state of charge used by said battery when said battery is in said recharge state by multiplying the difference between a gassing current, derived from said voltage sensor signal, and said current sensor signal, by the time since the last said computing time, and dividing by said rated capacity of said battery.

134. A method as defined in claim 133 including the further step of computing said absolute state of charge of said battery when said battery is in said recharge state by subtracting said state of charge used by said battery from said last computed absolute state of charge of said battery.

135. A method as defined in claim 134 including the further steps of computing said relative state of charge of said battery when said battery is in said recharge state by subtracting said factor from said absolute state of charge of said battery, said factor being determined from said last computed factor and said state of charge used by said battery.

136. A method as defined in claim 132 including the further step of computing said relative state of charge of said battery when said battery is in said recharge state by subtracting said factor of said battery from said absolute state of charge of said battery, said factor being determined from:

said last computed factor of said battery; and

the state of charge used by said battery.

137. A method as defined in claim 131 including the further step of computing said relative state of charge of said battery when said battery is in said discharge state based upon said voltage sensor signal and said current sensor signal.

138. A method as defined in claim 137 including the further step of computing said absolute state of charge of said battery when said battery is in said discharge state by adding said factor of said battery to said relative state of charge of said battery, said factor being determined from:

said rated capacity of said battery;

said current capacity of said battery;

said last computed factor;

said current sensor signal; and

said state of charge used by said battery.

139. A method as defined in claim 138 including the further step of limiting the computed values for said relative state of charge and said absolute state of charge responsive to said last computed stored absolute state of charge of said battery, said factor of said battery, and said state of charge used by said battery and a constant.