Method and apparatus for controlling the charging of a rechargeable battery to ensure that full charge is achieved without damaging the battery

• US 5,686,815 A
• Filed: 02/14/1995
• Issued: 11/11/1997
• Est. Priority Date: 02/14/1991
• Status: Expired due to Fees

• Current Assignee: Star Werks Inc.
• Original Assignee: Chartec Laboratories A/S
• Inventors: Reipur, John, Juul-Hansen, Ebbe
• Primary Examiner(s): TSO, EDWARD H
• Application Number:
  US08/388,680
• Time in Patent Office: 1,001 Days
• Field of Search: 320/2, 320/5, 320/21, 320/22, 320/30, 320/31, 320/39, 320/48, 320/35, 324/426, 324/427, 340/635, 429/90
• US Class Current: 320/116
• CPC Class Codes: G01R 31/374 with means for correcting the measurement for temperature or ageing
• CPC Class Codes: G01R 31/3832 without measurement of battery voltage
• CPC Class Codes: H01M 10/05 Accumulators with non-aqueous electrolyte H01M10/39 takes precedence
• CPC Class Codes: H01M 10/30 Nickel accumulators H01M10/34 takes precedence
• CPC Class Codes: H01M 10/345 Gastight metal hydride accumulators
• CPC Class Codes: H01M 10/4221 with battery type recognition
• CPC Class Codes: H01M 10/4257 Smart batteries, e.g. electronic circuits inside the housing of the cells or batteries
• 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: H02J 7/007184 in response to battery voltage gradient
• CPC Class Codes: H02J 7/007194 of the battery
• CPC Class Codes: Y02B 40/00 Technologies aiming at improving the efficiency of home appliances, e.g. induction cooking or efficient technologies for refrigerators, freezers or dish washers
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02E 60/13 Energy storage using capacitors

Abstract

In order to optimally control the charging of a rechargeable battery of one or more cells to ensure that full and rapid charge is achieved without damaging the battery, a maximum safe value (or sequence of values during the charging process) for one or more charging parameters is determined during a test charge, and subsequent charges of the battery are performed without exceeding the predetermined maximum value(s) for the charging parameter(s). Among the charging parameters contemplated for use are: the charging voltage potential placed across the battery terminals, the charging current supplied to the battery, the temperature of the battery cell and internal pressure of the battery cell as well as rates of changes of the parameters. In accordance with apparatus for practicing the invention, the value(s) of one or more predetermined maximum parameters are stored, and the corresponding actual charging parameter values are measured during the charging process and compared to the stored values to develop signals for controlling the charging process and thereby maintain the monitored parameter(s) no higher than the predetermined maximum value(s).

Claims

1. A method of charging a rechargeable battery having a pair of terminals, said method comprising:

selectively applying electrical power to the terminals of the battery;

monitoring at least one characteristic parameter of the charging process during at least part of the charging process;

comparing the characteristic charging parameter with corresponding stored reference parameters representing battery conditions;

selecting, based on said comparison, one of said stored sets of reference parameters;

determining the time (Tmax) at which the battery terminal voltage reaches a predetermined maximum value (Vmax);

determining a remaining period of charging time in accordance with the value of Tmax; and

terminating the charging process when said remaining period of time has expired.

4. The method of claim 1, wherein a first characteristic parameter is controlled during at least part of the charging process to obtain a predetermined desired sequence of a second characteristic parameter.

5. The method of claim 4, wherein the first characteristic parameter is the charging current and the second characteristic parameter is the charging voltage.

6. The method of claim 1, wherein the battery has at least two cells, the method further comprising:

monitoring the voltage of each cell; and

controlling the remaining period of the charging process in accordance with the voltage of the cell which first reaches a predetermined maximum cell voltage.

7. The method of claim 1, wherein the remaining charging period is determined by comparing the time at which the maximum voltage is reached with stored reference values and corresponding remaining charging periods.

8. The method of claim 1, wherein the characteristic charging parameter is selected from the group consisting of the potential across the battery terminals, the electric charging current supplied to the battery, the inner temperature of the battery, and the rate of change of any of such parameters.

9. The method of claim 1, further including the step of controlling, in accordance with at least one of the reference parameters of the selected set, the voltage supplied to the terminals of the battery over at least part of the process of charging the battery.

10. The method of claim 9, wherein the voltage supplied to the battery is controlled to maintain the electric charging current supplied to the battery at substantially the same maximum value during a major part of the charging process.

11. The method of claim 9, wherein voltage is supplied to the battery for a first relatively short period prior to the initiation of the charging process so that characteristic charging parameters can be measured, the results of these measurements determining whether the charging process is to be initiated.

12. The method of claim 9, wherein the voltage supplied to the battery is controlled so that the charging current is kept below a lower level during a first period and is raised to a higher level during a later period of the charging process.

13. The method of claim 1, wherein:

the characteristic charging parameter is measured at predetermined time intervals during charging;

the measured parameter values are compared with corresponding reference values; and

the relevant set of reference parameters is selected in accordance with the of comparison of such measure of such measured values and reference values.

14. The method of claim 13, wherein the characteristic charging parameter is the rate of change of the parameter values as a function of the lapsed charging time.

15. The method of claim 13, wherein parameter values are measured and the rates of change of the parameter values are determined at periodic first time intervals, each determination of the rates of change being based on parameter values measured at second time intervals, the second time interval being a multiple of the first time interval.

16. The method of claim 1, wherein the step of selectively applying electrical power to the terminals of the battery comprises pulse width modulating a constant voltage source.

17. The method of claim 14, wherein the determination of the rate of change is initiated when a measured value of the characteristic parameters exceeds a predetermined value.

18. The method of claim 1, wherein each parameter value is an average of a plurality of measurements within a certain period of time.

19. The method of claim 1, further comprising the step of terminating the application of electrical power to the battery if the charging period reaches a predetermined maximum period.

20. The method of claim 1, wherein the charging process is terminated if one of the parameter values measured exceeds a predetermined value for the respective parameter.

21. The method of claim 1, wherein the application of electrical power to the battery is interrupted if and when the characteristic parameter monitored deviates a predetermined amount from any of the corresponding values of the stored reference parameters.

22. The method of claim 1, wherein the charge state of the battery is maintained after termination of the charging process by feeding a pulsating current to the terminals of the battery.

23. The method of claim 1, wherein the battery is subjected to an initial testing prior to the actual charging process, said testing comprising

test charging the battery by supplying a first test charging current to the terminals of the battery for a first period of time,

monitoring at least one test charging parameter,

subsequently test discharging the battery for a, second period of time;

and

monitoring at least one test discharging parameter, wherein the first part of the actual charging process is controlled in accordance with the monitoring done during at least one of the test charging and test discharging processes.

24. The method of claim 23, wherein the battery is test charged by applying a predetermined test charging voltage to the terminals of the battery and monitoring at least one characteristic parameter.

25. The method of claim 24, wherein the test charging voltage is increased gradually or stepwise.

26. The method of claim 24, wherein the test charging and discharging procedures are performed at least one time.

2. An apparatus for charging a chargeable battery, said apparatus comprising:

a connector adapted to selectively effect an electrical connection between the battery and an electrical power source;

means for monitoring at least one characteristic parameter of a charging process during at least part of the battery charging process;

a memory containing indicia of a plurality of reference parameters representing different desirable charging processes;

means for comparing the monitored charging parameter with the reference parameters and for selecting, based on said comparison, one of said stored sets of reference parameters; and

means for determining the time (Tmax) at which the battery terminal voltage reaches a predetermined maximum value (Vmax); and

means for determining a remaining period of charging time in accordance with the value of Tmax.

3. A method of determining a process of charging a rechargeable battery having a capacity C, said method comprising:

test charging the battery to a substantially fully charged state by supplying thereto a relatively low test charging current, the relatively low test charging current being of such a level and being supplied during such a period of time that a rise in at least one charging parameter, comprising battery temperature, inner pressure of the battery and the charging voltage of the batteries and/or the cells thereof, is obtained during the test charging; and

determining a maximum value for the charging parameter during the test charging; and

carrying out subsequent charging of the battery at a higher rate controlled to avoid exceeding the determined maximum value for the charging parameter.

54. The method of claim 3, wherein the charging parameter is the difference between maximum and minimum temperatures during the test charging in said certain period of time.

55. The method of claim 3, wherein the test charging current supplied to the battery is 0.1-0.3 C/h.

56. The method of claim 3, wherein the test charging current supplied to the battery is 0.2-0.25 C/h.

57. The method of claim 3, wherein the test charging current supplied to the battery is 0.75-1.5 C/h.

58. The method of claim 57, wherein the maximum value of the charging or terminal voltage is determined as the maximum voltage obtained when the test charging current has been supplied to the battery for a predetermined period of time.

59. The method of claim 3, wherein the battery is partly charged at a slow rate and subsequently discharged at least once prior to said test charging and determining the maximum charging parameter.

60. The method of claim 3, wherein the relatively low test charging current is supplied to the battery for a predefined period of time such that a rise in at least one of the charging parameters has been obtained and no further essential parameter change has been detected.

61. The method of claim 60, wherein a first charging stop point is determined when no further rise in parameter value has been detected for a predetermined period of time.

62. The method of claim 61, wherein a capacity value of the battery is determined by determining a total first charging power supplied to the battery during the test charging until the first charging stop point is reached.

63. The method of claim 62, wherein the charging parameters for which a maximum value is determined comprises the terminal voltage of the battery, said test charging comprising a second test charging process wherein the battery is charged by a second test charging current which is substantially equal to the C-rate based on the capacity value determined.

64. The method of claim 63, wherein the maximum voltage is determined as the voltage measured across battery terminals at the point of time where the battery temperature has increased by the difference between maximum and minimum temperatures determined during test charging.

65. The method of claim 3, wherein the battery is substantially discharged before initiating test charging.

66. The method of claim 64, wherein:

the battery is charged with a substantially constant charging current during part of the subsequent charging process, the substantially constant charging current being several times the C-rate based on the capacity value determined;

the voltage of the battery terminal is monitored; and

when the maximum terminal voltage of the battery has been reached, the charging process is controlled to maintain the battery voltage substantially constant for the remaining period of the charging process.

67. The method of claim 66, wherein the battery has at least two cells, the voltage of each cell of the battery being monitored and the remaining period of the charging process being controlled based on the voltage of the cell first reaching the maximum cell terminal voltage.

68. The method of claim 66, wherein the stop point of the remaining charging period is determined by monitoring the charging current and when no further decrease in the charging current has been detected for a predetermined period of time, terminating the charging process.

69. The method of claim 66, wherein the subsequent charging process is stopped at a predetermined time, the remaining charging period being determined generally at the time when the maximum battery terminal voltage is reached.

70. The method of claim 66, wherein the remaining charging period is determined on the basis of a comparison of the battery terminal voltage sequence with stored reference voltage sequences.

71. The method of claim 69, wherein the remaining charging period is determined in accordance with the time when the maximum battery terminal voltage is reached.

72. The method of claim 69, wherein the stop point of the subsequent charging process and thus the remaining charging period is determined based on a comparison of the time at which the maximum voltage is reached with stored reference values and corresponding remaining charging periods.

73. The method of claim 66, wherein the subsequent charging process is stopped if the difference between maximum and minimum battery temperature exceeds the maximum value determined during test charging.

74. A battery system comprising:

a rechargeable battery including a pair of battery terminals;

an information means for containing information about the battery comprises at least one maximum value of a charging parameter determined by a method according to claim 3; and

a charging apparatus including a pair of charger terminals, means for releasably interconnecting the battery and the charging apparatus so that the battery terminals are in electrical conductive contact with the charger terminals, and information receiving means for receiving information from the information means of the battery, whereby the charging of the battery may be controlled based on said information.

75. The battery system of claim 74 further comprising control means for controlling the charging process based on the information received by the information receiving means.

76. A rechargeable battery for use in the battery system of claim 74, said battery comprising a pair of battery terminals and an information means for containing battery information in a form which may be sensed by suitable information receiving means of a corresponding battery charging apparatus.

77. The battery of claim 76, wherein the information means comprises an electronic memory for storing the battery information.

78. The battery of claim 76, wherein the battery information comprises information about the type of the battery, the capacity of the battery, other specifications of the battery, charging status of the battery, the condition of the various battery cells, the last charging process, the last discharging process, the time period lapsed since the last charging and discharging process, charging parameter algorithms, and the internal battery pressure.

79. The battery of claim 77, further comprising control means for controlling the charging process.

80. The battery of claim 79, wherein the control means are adapted to control charging of individual cells of the battery in response to the information received from the information means.

81. The battery of claim 77, further comprising an electronic display for displaying information from the memory.

82. The battery system of claim 74, wherein the information means comprise a temperature sensor for sensing the temperature of the battery.

83. The battery system of claim 74, wherein charging current is initially increased when the temperature sensed by the temperature sensor is low.

84. The battery system of claim 74, wherein charging voltage is initially increased when the temperature sensed by the temperature sensor is low.

85. The rechargeable battery of claim 76, further comprising:

at least two battery cells;

means for measuring the voltage of each battery cell; and

means for storing the measured cell voltages in the information means.

86. The battery of claim 85, wherein the information means further comprises a microprocessor.

87. The battery of claim 76, wherein the information means comprises a temperature sensor for sensing the temperature of the battery.

27. A method of charging a rechargeable battery having a pair of terminals, said method comprising:

connecting the terminals of the battery to an electrical power source;

initially test charging the battery by supplying a first test charging current to the terminals of the battery for a first period of time;

monitoring at least one test parameter;

subsequently test discharging the battery for a second period of time;

monitoring at least one test discharging parameter;

selecting values of at least one characteristic charging parameter based on the monitoring of the test charging and discharging processes;

subsequently at least partly charging the battery, wherein the battery charging process is controlled so that it is substantially in accordance with the values selected for the characteristic charging parameter, and terminating the charging process at the expiration of a remaining period of charging time determined when the battery terminal voltage has reached a predetermined maximum voltage.

28. The method of claim 27, wherein the battery is test charged by applying a predetermined test charging voltage to the terminals of the battery and monitoring at least one test parameter.

29. The method of claim 28, wherein the test charging voltage is increased gradually.

30. The method of claim 28, wherein the test charging and discharging processes are repeated at least one time.

31. The method of claim 27, wherein the test charging current supplied to the battery is relatively low.

32. The method of claim 27, wherein the battery is further charged subsequent to the partial charging, said further charging comprising:

monitoring the value of at least one characteristic parameter of the charging process during part of the battery charging process;

comparing the value of the characteristic charging parameter with corresponding values of stored reference parameters representing desirable charging processes;

selecting based on said comparison one of the stored sets of reference parameters; and

controlling at least part of the process of charging the battery in accordance with at least one reference parameter of the selected set.

33. The method of claim 32, wherein the charging parameter is selected from the group consisting of the potential across the battery terminals, the electric charging current supplied to the battery, the inner temperature of the battery, and the rate of change of any of such parameters.

34. The method of claim 32, wherein the charging process is controlled by controlling the voltage supplied to the terminals of the battery.

35. The method of claim 34, wherein the voltage supplied to the battery is controlled to maintain the electric charging current supplied to the battery at substantially the same maximum value during a major part of the charging process.

36. The method of claim 33, wherein voltage is briefly supplied to the battery prior to the initiation of the charging process so that charging parameters can be measured, the results of these measurements determining whether the characteristic charging process is to be initiated.

37. The method of claim 34, wherein the voltage supplied to the battery is controlled so that the charging current is kept below a lower level during a first period and is raised to a higher level during a later period of the charging process.

38. The method of claim 32, wherein:

the characteristic charging parameter is measured at predetermined time intervals during charging;

the measured parameter values are compared with corresponding reference values; and

the relevant set of reference parameters is selected in accordance with the of comparison of such measured values and reference values.

39. The method of claim 38, wherein the rate of change of the parameter values as a function of the charging time lapsed is compared with corresponding reference values.

40. The method of claim 38, wherein the parameter values are measured and the rates of change of the parameter values are determined at uniform first time intervals, each determination of the rates of change being based on parameter values measured at second time intervals, the second time interval being a multiple of the first time interval.

41. The method of claim 32, wherein the charging current fed to the battery is controlled by pulse width modulating a constant voltage source.

42. The method of claim 39, wherein the determination of the rate of change is initiated when a measured value of the characteristic parameters exceeds a predetermined value.

43. The method of claim 32, wherein each parameter value is an average of a plurality of measurements within a certain period of time.

44. The method of claim 32, wherein the charging period is restricted to a predetermined maximum period.

45. The method of claim 32, wherein the charging process is terminated if one of the parameter values measured exceeds a predetermined value for the respective parameter.

46. The method of claim 32, wherein the charging process is interrupted if and when the characteristic parameter monitored deviates a predetermined amount from any of the corresponding courses or values of the stored reference parameters.

47. The method of claim 32, wherein the charge state of the battery is maintained after termination of the charging process by feeding a pulsating current to the terminals of the battery.

48. The method of claim 32, wherein the battery is test charged by applying a predetermined test charging voltage to the terminals of the battery and monitoring at least one characteristic parameter.

49. The method of claim 48, wherein the test charging voltage is increased gradually.

50. The method of claim 48, wherein the test charging and discharging procedures are repeated at least one time.

51. An apparatus for charging a rechargeable battery, said apparatus comprising:

a connector disposed to selectively effect an electrical connection between the battery and an electrical power source;

means for initially test charging the battery by supplying a first test charging current to terminals of the battery for a first period of time;

means for monitoring at least one test charging parameter;

means for test discharging the battery for a, second period of time;

means for monitoring at least one test discharging parameter;

means for selecting a sequence of at least one charging parameter based on the monitoring of the test charging and discharging processes; and

means for controlling the process of partly charging the battery substantially in accordance with the sequence selected for the charging parameter, determining a remaining period of charging time when the value of the battery terminal voltage has reached a predetermined maximum voltage, and terminating the charging process when the remaining period of time has expired.

52. An apparatus according to claim 51, wherein the means for test charging the battery is adapted to apply a predetermined test charging voltage to the terminals of the battery, the monitoring means being adapted to monitor the test charging parameter.

53. The apparatus of claim 52, wherein the test charging means is adapted to increase the test charging voltage gradually.

88. A method of charging a rechargeable battery having terminals and a C-rate based on a predetermined capacity value of the rechargeable battery, said method comprising:

connecting an electrical power source to the terminals;

charging the battery with a substantially constant charging current during part of the charging process, said substantially constant charging current being several times the C-rate of the battery;

monitoring the voltage of the terminals;

controlling the charging process such that when a maximum terminal voltage has been reached, the battery voltage is maintained substantially constant for the remaining period of the charging process;

determining, at the time when the maximum terminal voltage has been reached, the remaining charging period of the charging process in accordance with the time when the maximum terminal voltage has been reached; and

stopping the charging process at the end of the remaining charging period.

89. The method of claim 88, wherein the battery has at least two cells, the voltage of each cell being monitored and the remaining period of the charging process being controlled based on the cell voltage first reaching the maximum cell terminal voltage.

90. The method of claim 88, wherein the remaining charging period is determined on the basis of a comparison of the terminal voltage with stored reference voltages.

91. The method of claim 88, wherein the stop point and thus the remaining charging period of time is determined based on a comparison of the time at which the maximum voltage is reached with stored reference values and corresponding remaining charging periods.

92. A method of charging a rechargeable battery, comprising:

storing indicia of charging periods corresponding to values of a predetermined charging parameter of the battery;

applying electrical energy to the battery;

sampling the parameter; and

terminating application of electrical energy to the battery in accordance with the charging periods corresponding to the sampled values of the predetermined charging parameter.

93. A method of charging a rechargeable battery, comprising:

storing indicia of a respective charging time period corresponding to each of a plurality of values of at least one characteristic parameter of the charging process during at least a predetermined part of the charging process;

applying electrical energy to the battery;

determining the value of the characteristic parameter for at least one point in the predetermined part of the charging process; and

terminating application of electrical energy to the battery in accordance with the charging time period corresponding to the value of the characteristic parameter.

94. The method of claim 93, wherein the storing indicia step comprises storing a plurality of sequences of values for the characteristic parameter under different charging conditions, and the method further includes the steps of:

applying a test charging current to the battery for an initial period;

determining the value of at least one test parameter associated with the charging during the initial period;

after the initial period, discharging the battery for a second period of time;

determining the value of at least one test parameter associated with discharging;

selecting one of the sequence or values of the charging parameter based on the test parameters; and

subsequently at least partly charging the battery substantially in accordance with the selected sequence of values.

95. The method of claim 93, wherein the step of applying electrical energy to the battery comprises controllably applying a current of a first predetermined value to the battery applying a current of a first predetermined value to the battery, and the method further comprises the steps of:

prior to applying a current of a first predetermined value to the battery, determining if the chemical reaction in the battery is normal.

96. The method of claim 95, further comprising the steps of:

if determined that the chemical reaction in the battery is not normal, applying a current to the battery of a predetermined value, less than the first predetermined value, for an initial time period.

97. The method of claim 93, comprising the steps of:

determining the value of at least the one characteristic parameter of the charging process at a plurality of sequential points in the process of charging the battery; and

terminating the charging in accordance with a time period determined in accordance with at least one of the determined values of the characteristic parameter.

98. The method of claim 93, comprising the steps of:

determining the value of the characteristic parameter of the charging process at a plurality of sequential points in the process of charging the battery; and

terminating the charging in accordance with the time period corresponding to the most recently determined value of the characteristic parameter.

99. The method of claim 93, comprising the steps of:

determining the value of the characteristic parameter of the charging process at a plurality of sequential points in the process of charging the battery; and

terminating the charging in accordance with a time period determined in accordance with at least one of the determined values of the characteristic parameter.

100. The method of claim 93, wherein the characteristic parameter is the rate of change of the voltage of the battery.

101. The method of claim 100, wherein the step of determining the value of the characteristic parameter comprises:

measuring the voltage of the battery at periodic intervals;

storing indicia of the measured voltage; and

for succeeding voltage measurements, determining the difference between the measured voltage and a prior voltage measured a predetermined number of intervals before.

102. The method of claim 100, wherein the electrical energy to the battery is cut off during periods when the voltage of the battery is measured.

103. The method of claim 93, wherein the step of applying electrical energy to the battery comprises the steps of:

controllably applying a current of a first predetermined value to the battery;

monitoring a predetermined parameter of the charging process;

controllably applying a current of a second predetermined value, less than the first predetermined value, to the battery in accordance with the value of the parameter reaching a first predetermined value;

and the part of the charging process for which indica is stored comprises at least part of the process during which the value of the current is the second predetermined value.

104. The method of claim 103, wherein the predetermined parameter of the charging process is related to the voltage of the battery and the monitoring step includes measuring the battery voltage, and the method further includes the step of interrupting the application of current to the battery while voltage measurements are taken.

105. The method of claim 93, wherein the step of applying electrical energy to the battery comprises the steps of:

controllably applying a constant current of a first predetermined value to the battery until the battery voltage reaches a predetermined maximum value; and

controllably applying a current to the battery to maintain a constant battery voltage subsequent to the battery voltage reaching the predetermined maximum value.

106. The method of claim 105 wherein the predetermined parameter of the charging process is related to the voltage of the battery and the monitoring step includes measuring the battery voltage, and the method further includes the step of interrupting the application of current to the battery while voltage measurements are taken.

107. The method of claim 93, wherein the step of applying electrical energy to the battery comprises the steps of:

applying pulse width modulated current pulses to the battery.

108. The method of claim 107, wherein the predetermined parameter of the charging process is related to the voltage of the battery and the monitoring step includes measuring the battery voltage between current pulses.

109. A method of charging a rechargeable battery, comprising:

storing reference values for at least one characteristic parameter of the charging process during at least part of the process of charging at least one type of battery;

connecting a source of electrical energy to the battery;

monitoring the value of at least the one characteristic parameter of the charging process during at least part of the process of charging the battery,

comparing the values of the charging parameter monitored with the stored corresponding reference values, and

determining the remaining period necessary to charge the battery based upon the stored reference values.

110. The method of claim 109, wherein the storing reference values step comprises storing a sequence of values for the characteristic parameter.

111. The method of claim 110, wherein the storing reference values step comprises storing a plurality of sequences of values for the characteristic parameter under different charging conditions, and the method further includes the steps of:

choosing, based upon the results of comparing the values of the charging parameter monitored with the stored corresponding reference values, one of the sequences of values for the characteristic parameter; and

determining the remaining period necessary to charge the battery based upon the chosen stored sequence of reference values.

112. The method of claim 111, wherein the different charging conditions comprise different starting states of charge.

113. The method of claim 111, further comprising the steps of:

comparing, at a plurality of times during at least part of the process of charging the battery, the values of the charging parameter monitored with the stored corresponding reference values,

choosing, based upon the results of the most recent comparing the values of the charging parameter monitored with the stored corresponding reference values, one of the sequences of values for the characteristic parameter; and

determining the remaining period necessary to charge the battery based upon the chosen stored sequence of reference values.

114. The method of claim 110, wherein the storing reference values step comprises storing a plurality of sequences of values for the characteristic parameter for different types of batteries, and the method further includes the steps of:

choosing, based upon the results of comparing the values of the charging parameter monitored with the stored corresponding reference values, one of the sequences of values for the characteristic parameter; and

determining the remaining period necessary to charge the battery based upon the chosen stored sequence of reference values.

115. The method of claim 109, further comprising the steps of:

comparing, at a plurality of times during at least part of the process of charging the battery, the values of the charging parameter monitored with the stored corresponding reference values,

redetermining the remaining period necessary to charge the battery based upon the stored reference values in accordance with successive comparisons.

116. A method of charging a rechargeable battery, comprising:

storing indicia of a respective period of time necessary to complete charging corresponding to each of a plurality of values of at least one characteristic parameter of the charging process;

controllably applying a current of a first predetermined value to the battery;

monitoring the battery voltage;

controllably applying a current of a second predetermined value, less than the first predetermined value to the battery in accordance with the battery voltage reaching a first predetermined value;

during a period in accordance with the battery voltage reaching a second predetermined value, determining the value of the one characteristic parameter; and

terminating the charging in accordance with the time period corresponding to the value of the characteristic parameter.

117. The method of claim 116, wherein the second predetermined battery voltage value equals the second predetermined battery voltage value.

118. The method of claim 116, wherein the period in accordance with the battery voltage reaching a second predetermined value is a period beginning upon the battery voltage reaching the second predetermined value.

119. The method of claim 116, comprising the steps of:

determining the value of the one characteristic parameter during at a plurality of sequential points during the period in accordance with the battery voltage reaching a second predetermined value; and

terminating the charging in accordance with the time period corresponding to at least one of the determined values of the characteristic parameter.

120. An apparatus for charging a rechargeable battery, said apparatus comprising:

an electrical power supply circuit;

a measuring device for generating indicia of the value of at least one characteristic parameter of the charging process at sequential points of time during charging;

a storage circuit for storing indicia of measured parameter values, calculated parameter values and reference values;

a control unit, cooperating with the power supply circuit and the storage circuit, for determining a possible stop point of time for the charging process at least some of the measurement points of time, the stop point time being determined in accordance with a comparison of the measured characteristic parameter with the reference values, and to determine an optimum remaining charging time and thereby an optimum stop point of time from a plurality of possible stop points of time resulting from such comparisons, each comparison being based on a correlation between parameter values at subsequent points of time and their distances in time from their respective possible stop point of time.

121. An apparatus according to claim 120, further comprising a switch cutting-off the charging current to the battery for a brief period before the voltage across the connection terminals of the battery is measured.

122. A method of charging a rechargeable battery having a pair of terminals, said method comprising

connecting an electrical power source to the terminals of the battery,

monitoring at least one charging parameter during at least part of the process of charging of the battery,

comparing a sequence of values of said at least one charging parameter with stored reference parameter sequences representing idealistic or desirable processes of charging the battery for different starting states of charge of the battery,

selecting the reference sequence corresponding to the sequence of values of said at least one charging parameter, and

controlling the process of charging the battery so as to cause the sequence of subsequent values of said at least one parameter to approximate the selected reference parameter sequence.

123. The method of claim 122, wherein said at least one charging parameter is selected from the group consisting of:

the potential across the battery terminals;

the magnitude of the charging current supplied to the battery;

the temperature of the battery;

the rate of change of any of such parameters; and

any combination thereof.

124. The method of claim 122, further including the step of briefly supplying voltage to the battery prior to the initiation of the charging process so that charging parameters can be measured, the results of these measurements determining whether the charging process is to be initiated.

125. The method of claim 122, wherein the process of charging is controlled by controlling the voltage supplied to the terminals of the battery.

126. The method of claim 125, wherein the voltage supplied to the battery is controlled so as to maintain the electric charging current supplied to the battery at substantially the same maximum value during a major part of the charging process.

127. An apparatus for charging a rechargeable battery, said apparatus comprising:

connecting means for connecting the battery to an electrical power source,

means for monitoring at least one charging parameter during at least part of the process of charging the battery,

storing means for storing a plurality of reference parameter sequences representing idealistic or desirable processes of charging the battery for various starting states of charge of the battery,

means for comparing the sequence of values of said at least one charging parameter with the stored reference parameter sequences and for selecting the reference course corresponding to the sequence of values of said at least one charging parameter, and

means for controlling the process of charging the battery so as to cause the sequence of subsequent values of said at least one parameter to the selected reference parameter sequence.

128. An apparatus according to claim 127, wherein the control means is adapted to briefly supply a voltage to the battery prior to the initiation of the charging process and to measure charging parameters and to determine in response to the measurement results whether the charging process is to be initiated.

129. An apparatus according to claim 127, wherein the control means is adapted to control the process of charging the battery by controlling the voltage supplied to the connecting means.

130. An apparatus according to claim 129, wherein the control means are adapted to control the voltage supplied to the connecting means so as to maintain the electric charging current supplied to the battery connected to the connecting means substantially at the same maximum value during a major part of the charging process.