Method of charging batteries and apparatus therefor

• US 4,392,101 A
• Filed: 01/05/1982
• Issued: 07/05/1983
• Est. Priority Date: 05/31/1978
• Status: Expired due to Term

• Current Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Original Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Inventors: Walter, Richard T., Saar, David A.
• Primary Examiner(s): SHOOP JR, WILLIAM M
• Application Number:
  US06/337,174
• Time in Patent Office: 546 Days
• Field of Search: 320/20, 320/22-24, 320/39, 320/40, 320/48
• US Class Current: 320/156
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H02J 7/00718 in response to charge current gradient
• CPC Class Codes: H02J 7/007184 in response to battery voltage gradient
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A method of fast charging batteries by means of precise analysis of the profile of the variation with time of a characteristic of the battery which is indicative of the variation in stored chemical energy as the battery is charged. The method specifically comprises analyzing the profile for the occurrence of a particular series of events preferably including one or more inflection points which precisely identify the point in time at which the application of a fast charge rate should be discontinued. Additional methods of analysis provide for termination or control of the charging current upon the occurrence of other events such as limiting values on time, voltage or voltage slope or a negative change in the level of stored energy.

Apparatus for performing these methods comprises a suitable power supply and a microcomputer for analyzing the profile and controlling the power supply.

Claims

1. A method of rapidly and efficiently charging a battery of the type having characteristic associated therewith that varies with the state of charge of the battery and in which the characteristic varies with time during charging to exhibit a plurality of inflection points prior to the battery attaining substantial full charge, the method comprising the steps of:

supplying electrical energy to the battery for charging thereof;

monitoring said characteristic drawn by the battery during charging;

analyzing the variation of said monitored characteristic with time to determine the occurrence of the last inflection point exhibited prior to the battery attaining substantial full charge; and

controlling the supply of electrical energy of the battery on the basis of the so-determined occurrence.

22. The method claimed in claims 1, 6, 10, 15, 18, or 19, whrein said monitoring step further comprises:

monitoring an electrical characteristic of the battery.

23. The method claimed in claim 22, wherein the monitoring step further comprises:

measuring the battery voltage.

24. The method claimed in claim 22, wherein the monitoring step further comprises:

measuring the current drawn by the battery during charging.

25. The method claimed in claim 24, wherein the monitoring step further comprises:

measuring the current drawn by the battery during charging at a constant value of voltage.

26. The method claimed in claim 1, 2, 3, 6, 7, or 15, wherein said controlling step further comprises:

discontinuing the supply of electrical energy to the battery.

27. The method claimed in claim 1, 2, 3, 6, 7, or 15, wherein said controlling step further comprises:

reducing the rate of supply of electrical energy to the battery to a predetermined rate to prevent self-discharge thereof.

28. The method claimed in claim 1, 5, 6, 7, 9, 10, 13, or 14, in which the battery is of the nickel-cadmium type.

62. The method claimed in claim 1, 2, 3, 4, 7, 15, 19 or 60, wherein said supplying step further comprises:

supplying the electrical energy to the battery at a rate greater than 0.2 C.

63. The method claimed in claim 1, 2, 3, 4, 7, 18, 19, or 60, wherein said monitoring step further comprises:

monitoring the characteristic on a periodic basis.

2. A method of rapidly and efficiently charging a battery of the type in which the voltage characteristic thereof varies with the state of charge of the battery and in which the voltage characteristic varies with time during charging to exhibit an inflection point just prior to the battery attaining substantial full charge, the inflection point characterized by a change in sign of the second derivative of the voltage characteristic variation with time, the method comprising the steps of:

supplying electrical energy to the battery for charging thereof;

monitoring said voltage characteristic of the battery during charging;

analyzing the variation of said monitored voltage characteristic with time to determine the occurrence of the inflection point exhibited just prior to the battery attaining substantial full charge by determining a change in sign of the second derivative of said voltage characteristic variation with time; and

controlling the supply of electrical energy to the battery on the basis of the so-determined occurrence.

3. A method of rapidly and efficiently charging a battery of the type in which the voltage characteristic thereof varies with the state of charge of the battery and in which the voltage characteristic varies with time during charging to exhibit an inflection point prior to the battery attaining substantial full charge, the inflection point characterized by a change in sign of the second derivative of the voltage characteristic variation with time from a positive to a negative value, the method comprising the steps of:

supplying electrical energy to the battery for charging thereof;

monitoring said voltage characteristic of the battery during charging;

analyzing the variation of said monitored voltage characteristic with time to determine the occurrence of the inflection point exhibited prior to the battery attaining substantial full charge by determining a change in sign from a positive to a negative value of the second derivative of said voltage characteristic variation with time; and

controlling the supply of electrical energy to the battery on the basis of the so-determined occurrence.

4. A method of rapidly and efficiently charging a battery of the type in which the current characteristic drawn by the battery during charging varies with the state of charge of the battery and in which the current characteristic varies with time during charging to exhibit an inflection point just prior to the battery attaining substantial full charge by determining a change in sign of the second derivative of said current characteristic variation with time, the method comprising the steps of:

supplying electrical energy to the battery for charging thereof;

measuring said current characteristic drawn by the battery during charging;

analyzing the variation of said monitored current characteristic with time to determine the occurrence of the inflection point exhibited just prior to the battery attaining substantial full charge by determining a change in sign of the second derivative of said current characteristic variation with time; and

controlling the supply of electrical energy of the battery on the basis of the so-determined occurrence.

5. A method of rapidly and efficiently charging a battery of the type in which the current characteristic drawn by the battery during charging varies with the state of charge of the battery and in which the current characteristic varies with time during charing to exhibit an inflection point prior to the battery attaining substantial full charge, the inflection point characterized by a change in sign of the second derivative of the current characteristic variation with time from a negative to a positive value, the method comprising the steps of:

supplying electrical energy to the battery for charging thereof;

monitoring said current characteristic drawn by the battery during charging;

analyzing the variation of said monitored current characteristic with time to determine the occurrence of the inflection point exhibited prior to the battery attaining substantial full charge by determining a change in sign of the second derivative of said current characteristic variation from a negative to a positive value; and

controlling the supply of electrical energy of the battery on the basis of the so-determined occurrence.

6. A method of rapidly and efficiently charging a battery of the type having a characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the characteristic with time during charging exhibits an inflection point prior to the battery attaining substantial full charge and another inflection point that precedes the first-mentioned inflection point, the method comprising the steps of:

supplying electrical energy to the battery for charging thereof;

monitoring said characteristic of the battery during charging;

analyzing the variation of said monitored characteristic with time to determine the occurrence of the first-mentioned inflection point; and

controlling the supply of electrical energy to the battery on the basis of the so-determined occurrence.

7. A method of rapidly and efficiently charging a battery of the type having a characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the characteristic with time during charging exhibits a first and a succeeding inflection point prior to the battery attaining a predetermined charge level, the method comprising the steps of:

supplying electrical energy to the battery for charging thereof;

monitoring said characteristic of the battery during charging;

analyzing the variation of said monitored characteristic with time to determine the occurrence of the succeeding inflection point; and

controlling the supply of electrical energy to the battery on the basis of the so-determined occurrence.

8. A method of rapidly and efficiently charging a battery of the type having a characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the characteristic with time during charging exhibits an opposed pair of inflection points prior to the battery attaining substantial full charge, the method comprising the steps of:

supplying electrical energy to the battery for charging thereof;

monitoring said characteristic of the battery during charging;

analyzing the variation of said monitored characteristic with time to determine the occurrence of the last inflection point of the opposed pair of inflection points; and

controlling the supply of electrical energy to the battery on the basis of the so-determined occurrence of the last inflection point of the opposed pair of inflection points.

9. A method of rapidly and efficiently charging a battery of the type having a characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the characteristic with time during charging exhibits a plurality of inflection points prior to the battery attaining substantial full charge, the method comprising the steps of:

supplying electrical energy to the battery for charging thereof;

monitoring said characteristic of the battery during charging;

analyzing the variation of said monitored characteristic with time to determine the occurrence of a second inflection point of the plurality of inflection points; and

controlling the supply of electrical energy to the battery on the basis of the so-determined occurrence.

10. A method of rapidly and efficiently charging a battery of the type having a characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the characteristic with time during charging exhibits an inflection point prior to the battery attaining substantial full charge and another inflection point that precedes the first-mentioned inflection point, the method comprising the steps of:

supplying electrical energy to the battery for charging thereof;

monitoring said characteristic of the battery during charging;

analyzing the variation of said monitored characteristic with time to determine the occurrence of a sequence of the preceding and the first-mentioned inflection points; and

controlling the supply of electrical energy to the battery on the basis of the so-determined sequential occurrence.

11. A method of rapidly and efficiently charging a battery of the type having a characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the characteristic with time during charging exhibits a first and a succeeding inflection point prior to battery attaining a predetermined charge level, the method comprising the steps of:

supplying electrical energy to the battery for charging thereof;

monitoring said characteristic of the battery during charging;

analyzing the variation of said monitored characteristic with time to determine the occurrence of a sequence of the first and the succeeding inflection points; and

controlling the supply of electrical energy to the battery on the basis of the so-determined sequential occurrence.

12. A method of rapidly and efficiently charging a battery of the type having a characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the characteristic with time during charging exhibits an opposed pair of inflection points prior to battery attaining substantial full charge, the method comprising the steps of:

supplying electrical energy to the battery for charging thereof;

monitoring said characteristic of the battery during charging;

analyzing the variation of said monitored characteristic with time to determine the occurrence of a sequence of the opposed pair of inflection points; and

controlling the supply of electrical energy to the battery on the basis of the so-determined sequential occurrence.

13. A method for rapidly and efficiently charging a battery of the type having a voltage characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the voltage characteristic with time during charging exhibits inflection points prior to the battery attaining substantial full charge in which each inflection point is characterized by a change in sign of the second derivative of the voltage characteristic, the method comprising the steps of:

supplying electrical energy to the battery for charging thereof;

monitoring said voltage characteristic of the battery during charging;

analyzing the variation of said monitored voltage characteristic with time to determine the occurrence of a sequence of inflection points characterized by a change in the sign of the second derivative of said voltage characteristic from a negative to a positive value and a succeeding change in sign of the second derivative of said voltage characteristic from a positive to a negative value; and

controlling the supply of electrical energy to the battery on the basis of the so-determined sequential occurrence.

14. A method of rapidly and efficiently charging a battery of the type in which the current characteristic drawn by the battery during charging varies with the state of charge of the battery and in which the variation of the current characteristic with time during charging exhibits inflection points prior to the battery attaining substantial full charge in which each inflection point is characterized by a change in sign of the second derivative of the current characteristic, the method comprising the steps of:

supplying electrical energy to the battery for charging thereof;

monitoring said current characteristic of the battery during charging;

analyzing the variation of said monitored current characteristic with time to determine the occurrence of a sequence of inflection points characterized by a change in sign of the second derivative of said current characteristic from a positive to a negative value and a succeeding change in sign of the second derivative of said current characteristic from a negative to a positive value; and

controlling the supply of electrical energy to the battery on the basis of the so-determined sequential occurrence.

15. A method of rapidly and efficiently charging a nickel-cadmium battery in which the voltage varies with the state of charge of the battery and in which the variation of the voltage with time during charging exhibits an inflection point prior to the battery attaining substantial full charge and another inflection point that precedes the first-mentioned inflection point, the method comprising the steps of:

supplying electrical energy to the battery for charging thereof;

monitoring said voltage characteristic of the battery during charging;

analyzing the variation of said monitored voltage characteristic with time to determine the occurrence of the first-mentioned inflection point; and

controlling the supply of electrical energy to the battery on the basis of the so-determined occurrence of the first-mentioned inflection point.

16. A method of rapidly and efficiently charging a battery of the type having a characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the characteristic with time during charging exhibits an inflection point just prior to the battery attaining substantial full charge, the method comprising the steps of:

supplying electrical energy to the battery for charging thereof;

monitoring said characteristic of the battery during charging;

analyzing the variation of said characteristic with time to determine the occurrence of said inflection point that occurs just prior to the battery attaining substantial full charge and to determine the occurrence of a predetermined variation of said characteristic that comprises a control indicium for reducing the supply of electrical energy to the battery; and

reducing the supply of electrical energy to the battery upon the first occurrence of a one of;

(a) said inflection point,

(b) a control indicium for reducing the supply of electrical energy to the battery.

20. The method claimed in claim 16, 17, 18, or 19, wherein said control indicium for reducing the supply of electrical energy to the battery comprises the occurrence of a one of:

the variation of said characteristic ceasing to be monotonic;

the value of said characteristic decreasing to a predetermined limit;

the value of said characteristic increasing to a predetermined limit;

the slope of the variation of said characteristic attaining a predetermined limit.

21. The method claimed in claim 16, 17, 18, or 19, 20, wherein said reducing step further comprises:

reducing the supply of electrical energy to the battery upon the passage of a predetermined amount of time.

17. A method of rapidly and efficiently charging a battery of the type having a characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the characteristic with time during charging exhibits an inflection point just prior to the battery attaining a predetermined charge level, and at least one other inflection point that precedes said first-mentioned inflection point, the method comprising the steps of:

supplying electrical energy to the battery for charging thereof;

monitoring said characteristic of the battery during charging;

analyzing the variation of said characteristic with time to determine the occurrence of said first-mentioned inflection point and to determine the occurrence of a predetermined variation of said characteristic that comprises a control indicium for reducing the supply of electrical energy to the battery; and

reducing the supply of electrical energy to the battery upon the first occurrence of a one of;

(a) said first-mentioned inflection point,

(b) a control indicium for reducing the supply of electrical energy to the battery.

18. A method of rapidly and efficiently charging a battery of the type having a characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the characteristic with time during charging exhibits a sequence of a first and a successive inflection point prior to the battery attaining substantial full charge, the method comprising the steps of:

supplying electrical energy to the battery for charging thereof;

monitoring said characteristic of the battery during charging;

analyzing the variation of said characteristic with time to determine the occurrence of said sequence of a first and a successive inflection point and to determine the occurrence of a predetermined variation of said characteristic that comprises a control indicium for reducing the supply of electrical energy to the battery; and

reducing the supply of electrical energy to the battery upon the first occurrence of a one of;

(a) said sequence of a first and a successive inflection point,

(b) a control indicium for reducing the supply of electrical energy to the battery.

19. A method of rapidly and efficiently charging a nickel-cadmium battery of the type having a characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the characteristic with time during charging exhibits an opposed pair of inflection points prior to the battery attaining substantial full charge, the method comprising the steps of:

supplying electrical energy to the battery for charging thereof;

monitoring said characteristic of the battery during charging;

analyzing the variation of said characteristic with time to determine the occurrence of said opposed pair of inflection points and to determine the occurrence of a predetermined variation of said characteristic that comprises a control indicium for reducing the supply of electrical energy to the battery; and

reducing the supply of electrical energy to the battery upon the first occurrence of a one of;

(a) said opposed pair of inflection points,

(b) a control indicium for reducing the supply of electrical energy to the battery.

29. An apparaus for charging a battery of the type having a characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the characteristic with time during charging exhibits a plurality of inflection points prior to the battery attaining substantial full charge, said apparatus comprising:

means for supplying electrical energy to the battery for charging thereof; and

means connected to said supply means for monitoring the characteristic during charging, for analyzing the so-monitored characteristic with time to determine the occurrence of the last inflection point exhibited prior to the battery attaining substantial full charge, and for controlling said supply means to control the supply of electrical energy to the battery.

48. The apparatus claimed in claim 29, 31, 33, 35, 38, or 44, wherein said second-mentioned means comprises a stored-program controlled means.

49. The apparatus claimed in claim 48, wherein said stored-program controlled means comprises a stored-program processor controlled means.

50. The apparatus claimed in claim 48, wherein said stored-program controlled means further comprises:

means for analyzing the so-monitored characteristic with time to determine the occurrence of a predetermined variation of the monitored characteristic that comprises a control indicium for controlling the supply of electrical energy to the battery.

51. The apparatus claimed in claim 50, wherein said means for analyzing to determine the occurrence of a control indicium comprises means for determining the occurrence of a one of:

the variation of the characteristic ceasing to be monotonic;

the value of the characteristic decreasing to a predetermined limit;

the value of the characteristic increasing to a predetermined limit;

the slope of the variation of the characteristic attaining a predetermined limit.

52. The apparatus claimed in claim 48, wherein said stored-program controlled means further comprises:

means for reducing the supply of electrical energy to the battery upon the passage of a predetermined amount of time.

59. The apparatus claimed in claim 29, 30, 31, 34, 38, or 44, wherein said battery is a nickel-cadmium battery.

30. An apparatus for charging a battery of the type having a voltage characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the voltage characteristic with time during charging exhibits an inflection point just prior to the battery attaining substantial full charge, the inflection point characterized by a change in sign of the second derivative of the voltage characteristic variation with time, said apparatus comprising:

means for supplying electrical energy to the battery for charging thereof; and

means connected to said supply means for monitoring the voltage characteristic during charging, for analyzing the so-monitored voltage characteristic with time to determine the occurrence of the inflection point exhibited just prior to the battery attaining substantial full charge by determining a change in sign of the second derivative of the voltage characteristic variation with time, and for controlling said supply means to control the supply of electrical energy to the battery.

53. The apparatus claimed in claim 30, 33, 34, 35, 38, or 43, wherein said second-mentioned means further comprises:

means for analyzing the variation of said monitored characteristic with time to determine the occurrence of a predetermined variation of said characteristic that comprises a control indicium for controlling said supply means.

54. The apparatus claimed in claim 53, wherein said means for analyzing to determine the occurrence of a control indicium comprises means for determining the occurrence of a one of:

the variation of the characteristic ceasing to be monotonic;

the value of characteristic decreasing to a predetermined limit;

the value of the characteristic increasing to a predetermined limit;

the slope of the variation of the characteristic attaining a predetermined limit.

55. The apparatus claimed in claim 53, wherein said stored-program controlled means further comprises:

means for reducing the supply of electrical energy to the battery upon the passage of a predetermined amount of time.

31. An apparatus for charging a battery of the type having a voltage characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the voltage characteristic with time during charging exhibits an inflection point prior to the battery attaining substantial full charge, the inflection point characterized by a change in sign of the second derivative of the voltage characteristic variation with time from a positive to a negative value, said apparatus comprising:

means for supplying electrical energy to the battery for charging thereof; and

means connected to said supply means for monitoring the voltage characteristic during charging, for analyzing the so-monitored voltage characteristic with time to determine the occurrence of the inflection point exhibited prior to the battery attaining substantial full charge by determining a change in sign from a positive to a negative value of the second derivative of the voltage characteristic variation with time, and for controlling said supply means to control the supply of electrical energy to the battery.

32. An apparatus for charging a battery of the type having a current characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the current characteristic with time during charging exhibits an inflection point just prior to the battery attaining substantial full charge, the inflection point characterized by a change in sign of the second derivative of the current variation with time, said apparatus comprising:

means for supplying electrical energy to the battery for charging thereof; and

means connected to said supply means for monitoring the current characteristic during charging, for analyzing the so-monitored characteristic with time to determine the occurrence of the inflection point exhibited just prior to the battery attaining substantial full charge by determining a change in sign of the second derivative of the current characteristic with time, and for controlling said supply means to control the supply of electrical energy to the battery.

33. An apparatus for charging a battery of the type having a current characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the current characteristic with time during charging exhibits an inflection point prior to the battery attaining substantial full charge, the inflection point characterized by a change in the sign of the second derivative of the current variation with time from a negative to a positive value, said apparatus comprising:

means for supplying electrical energy to the battery for charging thereof; and

means connected to said supply means for monitoring the current characteristic during charging, for analyzing the so-monitored characteristic with time to determine the occurrence of the inflection point exhibited prior to the battery attaining substantial full charge by determining a change in sign from a negative to a positive value of the second derivative of the current characteristic with time, and for controlling said supply means to control the supply of electrical energy to the battery.

34. An apparatus for charging a battery of the type having a characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the characteristic with time during charging exhibits an inflection point prior to the battery attaining substantial full charge and another inflection point that precedes the first-mentioned inflection point, said apparatus comprising:

means for supplying electrical energy to the battery for charging thereof; and

means connected to said supply means for monitoring the characteristic during charging, for analyzing the so-monitored characteristic with time to determine the occurrence of the first-mentioned inflection point, and for controlling said supply means to control the supply of electrical energy to the battery.

35. An apparatus for charging a battery of the type having a characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the characteristic with time during charging exhibits a first and a succeeding inflection point prior to the battery attaining substantial full charge, said apparatus comprising:

means for supplying electrical energy to the battery for charging thereof; and

means connected to said supply means for monitoring the characteristic during charging, for analyzing the so-monitored characteristic with time to determine the occurrence of the succeeding inflection point, and for controlling said supply means to control the supply of electrical energy to the battery.

36. An apparatus for charging a battery of the type having a characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the characteristic with time during charging exhibits an opposed pair of inflection points prior to the battery attaining a predetermined charge level, said apparatus comprising:

means for supplying electrical energy to the battery for charging thereof;

means connected to said supply means for monitoring the characteristic during charging;

means connected to said monitoring means for analyzing the so-monitored characteristic with time to determine the occurrence of the last inflection point of the opposed pair of inflection points; and

means connected to said supply means for controlling said supply means in response to said analyzing means.

37. An apparatus for charging a battery of the type having a characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the characteristic with time during charging exhibits a plurality of inflection points prior to the battery attaining substantial full charge, said apparatus comprising:

means for supplying electrical energy to the battery for charging thereof;

means connected to said supply means for monitoring the characteristic during charging;

means connected to said monitoring means for analyzing the so-monitored characteristic with time to determine the occurrence of a second inflection point of the plurality of inflection points; and

means connected to said supply means for controlling said supply means in response to said analyzing means.

56. The apparatus claimed in claim 37, 39, or 40, wherein said means for analyzing further comprises:

means for analyzing the variation of said monitored characteristic with time to determine the occurrence of a predetermined variation of said characteristic that comprises a control indicium for controlling said supply means.

57. The apparatus claimed in claim 56, wherein said means for analyzing to determine the occurrence of a control indicium comprises means for determining the occurrence of a one of:

the variation of the characteristic ceasing to be monotonic;

the value of the characteristic decreasing to a predetermined limit;

the value of the characteristic increasing to a predetermined limit.

58. The apparatus claimed in claim 56, wherein said stored-program controlled means further comprises:

means for reducing the supply of electrical energy to the battery upon the passage of a predetermined amount of time.

38. An apparatus for charging a battery of the type having a characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the characteristic with time during charging exhibits an inflection point prior to the battery attaining substantial full charge and another inflection point that precedes the first-mentioned inflection point, said apparatus comprising:

means for supplying electrical energy to the battery for charging thereof; and

means connected to said supply means for monitoring the characteristic during charging, for analyzing the so-monitored characteristic with time to determine the occurrence of sequence of the preceding and the first-mentioned inflection points, and for controlling said supply means to control the supply of electrical energy to the battery.

39. An apparatus for charging a battery of the type having a characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the characteristic with time during charging exhibits a first and a succeeding inflection point prior to battery attaining a predetermined charge level, said apparatus comprising:

means for supplying electrical energy to the battery for charging thereof;

means connected to said supply means for monitoring the characteristic during charging;

means connected to said monitoring means for analyzing the so-monitored characteristic with time to determine the occurrence of a sequence of the first and the succeeding inflection points; and

means connected to said supply means for controlling said supply means in response to said analyzing means.

40. An apparatus for charging a battery of the type having a characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the characteristic with time during charging exhibits an opposed pair of inflection points prior to battery attaining substantial full charge, said apparatus comprising:

means for supplying electrical energy to the battery for charging thereof;

means connected to said supply means for monitoring the characteristic during charging;

means connected to said monitoring means for analyzing the so-monitored characteristic with time to determine the occurrence of a sequence of the opposed pair of inflection points; and

means connected to said supply means for controlling said supply means in response to said analyzing means.

41. An apparatus for charging a battery of the type having a voltage characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the characteristic with time during charging exhibits inflection points prior to the battery attaining substantial full charge in which each inflection point is characterized by a change in sign of the second derivative of the voltage characteristic, said apparatus comprising:

means for supplying electrical energy to the battery for charging thereof; and

means connected to said supply means for monitoring the voltage characteristic during charging, for analyzing the so-monitored characteristic with time to determine the occurrence of a sequence inflection points characterized by a change in the sign of the second derivative of the voltage characteristic from a negative to a positive value and a succeeding change in sign of the second derivative of the voltage characteristic from a positive to a negative value, and for controlling said supply means to control the supply of electrical energy to the battery.

42. An apparatus for charging a battery of the type having a current characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the current characteristic with time during charging exhibits inflection points prior to the battery attaining substantial full charge in which each inflection point is characterized by a change in sign of the second derivative of the current characteristic, said apparatus comprising:

means for supplying electrical energy to the battery for charging thereof; and

means connected to said supply means for monitoring said characteristic during charging, for analyzing the so-monitored characteristic with time to determine the occurrence of a sequence of inflection points characterized by a change in sign of the second derivative of the current characteristic from a positive to a negative value and a succeeding change in sign of the second derivative of the current characteristic from a negative to a positive value, and for controlling said supply means to control the supply of electrical energy to the battery.

43. An apparatus for charging a nickel-cadmium battery having a voltage characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the voltage characteristic with time during charging exhibits an inflection point prior to the battery attaining substantial full charge and another inflection point that precedes the first-mentioned inflection point, said apparatus comprising:

supply means for supplying electrical energy to the battery for charging thereof; and

stored-program controlled means connected to said supply means for monitoring the characteristic during charging, for analyzing the so-monitored characteristic with time to determine the occurrence of the first-mentioned inflection point, and for controlling said supply means to control the supply of electrical energy to the battery.

44. An apparatus for charging a battery of the type having a characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the characteristic with time during charging exhibits an inflection point just prior to the battery attaining substantial full charge, said apparatus comprising:

means for supplying electrical energy to the battery for charging thereof; and

means connected to said supply means for monitoring the characteristic during charging, for analyzing the so-monitored characteristic with time to determine the occurrence of the inflection point that occurs just prior to the battery attaining substantial full charge and the occurrence of a predetermined variation of the monitored characteristic that comprises control indicium for controlling said supply means, and for controlling said supply means to control the supply of electrical energy to the battery.

45. An apparatus for charging a battery of the type having a characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the characteristic with time during charging exhibits an inflection point prior to the battery attaining a predetermined charge level and another inflection point that precedes the first-mentioned inflection point, said apparatus comprising:

means for supplying electrical energy to the battery for charging thereof;

means connected to said supply means for monitoring the characteristic during charging;

means connected to said monitoring means for analyzing the so-monitored characteristic with time to determine the occurrence of the first-mentioned inflection point and the occurrence of a predetermined variation of the monitored characteristic that comprises control indicium for controlling said supply means; and

means connected to said supply means to control the supply of electrical energy to the battery in response to said analyzing means.

46. An apparatus for charging a battery of the type having a characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the characteristic with time during charging exhibits a sequence of a first and a successive inflection point, said apparatus comprising:

means for supplying electrical energy to the battery for charging thereof;

means connected to said supply means for monitoring the characteristic during charging;

means connected to said monitoring means for analyzing the so-monitored characteristic with time to determine the occurrence of a sequence of the first and successive inflection points and the occurrence of a predetermined variation of the monitored characteristic that comprises control indicium for controlling said supply means; and

means connected to said supply means to control the supply of electrical energy to the battery in response to said analyzing means.

47. An apparatus for charging a nickel-cadmium battery of the type having a voltage characteristic associated therewith that varies with the state of charge of the battery and in which the variation of the voltage characteristic with time during charging exhibits an opposed pair of inflection points, said apparatus comprising:

means for supplying electrical energy to the battery for charging thereof; and

means connected to said supply means for monitoring the voltage characteristic during charging, for analyzing the so-monitored characteristic with time to determine the occurrence of the last inflection point of the opposed pair and the occurrence of a predetermined variation of the monitored characteristic that comprises control indicium for controlling said supply means, and for controlling said supply means to control the supply of electrical energy to the battery.

60. A method of rapidly and efficiently charging a battery of the type having an electrical characteristic associated therewith that varies with the state of charge of the battery and in which the characteristic varies with time during charging to exhibit an inflection point just prior to the battery attaining substantial full charge, the method comprising the steps of:

supplying electrical energy to the battery for charging thereof;

monitoring said electrical characteristic of the battery during charging;

analyzing the variation of said monitored characteristic with time to determine the occurrence of the inflection point exhibited just prior to the battery attaining substantial full charge; and

discontinuing the supply of electrical energy to the battery on the basis of the so-determined occurrence.

61. The method claimed in claim 60, wherein said discontinuing step further comprises:

discontinuing the supply of electrical energy to the battery and subsequently supplying electrical energy to the battery at a predetermined maintenance rate not less than the internal discharge rate of the battery.

64. The method claimed in claim 60, wherein said discontinuing step further comprises:

discontinuing the supply of electrical energy to the battery and subsequently supplying electrical energy to the battery for a selected time period on a recurring basis.