Fast battery charger

• US 5,363,031 A
• Filed: 03/23/1992
• Issued: 11/08/1994
• Est. Priority Date: 12/05/1989
• Status: Expired due to Term

• Current Assignee: Intermec (Honeywell International Inc.)
• Original Assignee: Norand Corporation (Baker Hughes Company)
• Inventors: Miller, Phillip, Koenck, Steven E., Becker, Ronald D.
• Primary Examiner(s): Peckman, Kristine L.
• Application Number:
  US07/859,591
• Time in Patent Office: 960 Days
• Field of Search: 320/21, 320/31, 320/32, 320/35, 320/36, 320/39, 320/40, 320/43, 320/48, 320/22, 320/23, 320/24, 320/20
• US Class Current: 320/115
• CPC Class Codes: B60L 2260/162 of electrical cells or capacitors
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/374 with means for correcting the measurement for temperature or ageing
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• CPC Class Codes: G06F 1/263 Arrangements for using multiple switchable power supplies, e.g. battery and AC G06F1/30 takes precedence
• CPC Class Codes: H01M 10/425 Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing printed circuits H05K1/00
• CPC Class Codes: H01M 10/4257 Smart batteries, e.g. electronic circuits inside the housing of the cells or batteries
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• 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: H01M 10/486 for measuring temperature
• CPC Class Codes: H01M 50/213 adapted for cells having curved cross-section, e.g. round or elliptic H01M50/209, H01M50/216 take precedence
• CPC Class Codes: H01M 50/50 Current conducting connections for cells or batteries
• CPC Class Codes: H01M 6/5044 Cells or batteries structurally combined with cell condition indicating means
• CPC Class Codes: H01M 6/505 Cells combined with indicating means for external visualization of the condition, e.g. by change of colour or of light intensity
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
• CPC Class Codes: H02J 7/00036 Charger exchanging data with battery
• CPC Class Codes: H02J 7/00038 using passive battery identification means, e.g. resistors or capacitors identification by mechanical connections H02J7/0045
• CPC Class Codes: H02J 7/00047 with provisions for charging different types of batteries
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]
• CPC Class Codes: H02J 7/0068 Battery or charger load switching, e.g. concurrent charging and load supply H02J7/0013 takes precedence
• CPC Class Codes: H02J 7/0069 : Charging or discharging for charge maintenance, battery initiation or rejuvenation
• CPC Class Codes: H02J 7/0071 : with a programmable schedule
• CPC Class Codes: H02J 7/00711 : with introduction of pulses during the charging process
• CPC Class Codes: H02J 7/00712 : the cycle being controlled or terminated in response to electric parameters
• CPC Class Codes: H02J 7/00714 : in response to battery charging or discharging current
• CPC Class Codes: H02J 7/007194 : of the battery
• CPC Class Codes: H02J 9/061 : for DC powered loads
• CPC Class Codes: Y02E 60/10 : Energy storage using batteries
• CPC Class Codes: Y10S 320/10 : Nonbattery load controls charging

Abstract

In an exemplary fast charging system, a hand-held computerized terminal with rechargeable batteries therein may be bodily inserted into a charger receptacle. The terminal may have volatile memory and other components requiring load current during charging., The system may automatically identify battery type and progressively increase charging current while monitoring for an increase in battery terminal voltage to ascertain the level of load current. The battery temperature may be brought into a relationship to surrounding temperature such that by applying a suitable overcharge current value and observing any resultant temperature increase, the level of remaining battery charge can be determined. For example, if the battery is found to be relatively fully discharged, a relatively high fast-charge rate may be safely applied while monitoring battery temperature. If the battery is initially relatively fully charged or reaches such a state during fast charge, the system may automatically dynamically select a maintenance charge rate according to battery type and temperature. A preferred system may automatically recharge the batteries of a portable device according to an optimum schedule of essentially maximum safe charging rates as a function of battery temperature, and thereafter safely maintain the batteries at essentially fully charged condition in readiness for maximum duration portable operation.

Claims

1. In a battery conditioning system,

(a) rechargeable battery means for supplying operating current during a number of hours of portable operation so as to become progressively discharged as a result,

(b) battery conditioning system means for coupling with said rechargeable battery means for supplying current to said rechargeable battery means during a battery conditioning cycle, after a period of portable operation,

(c) said battery conditioning system means comprising computer means having input means for receiving measures of battery temperature at successive times during such battery conditioning cycle, and

(d) current control means for coupling with said rechargeable battery means for controlling the rate of current flow to the rechargeable battery means during a battery conditioning cycle,

(e) said computer means having output means coupled with said current control means for varying the rate to said rechargeable battery means during conditioning cycle as a function of said measures of battery temperature as monitored by said computer means,

(f) said current control means providing a relatively low rate of current flow to said battery means suitable for a relatively low value of battery temperature during overcharge of the battery means, and providing a multiplicity of different higher rates of current flow to said battery means each of which is higher than said relatively low rate of current flow, and each of which is suitable for a respective different higher value of battery temperature during overcharge of said battery means,

(g) said computer means being responsive to one of said measures of battery temperature representative of said relatively low value of battery temperature to select said relatively low rate of current flow to said battery means, and being responsive to respective others of said measures of battery temperature representing the respective different higher values of battery temperature to select respective ones of said multiplicity of different higher rates of current flow to said battery means, such that said battery conditioning cycle can be carried out under a wide range of environmental conditions while yet assuring a battery conditioning cycle which is suitable during overcharge of said battery means.

2. In a battery conditioning system according to claim 1, said current control means having about ten or more of said different higher rates of current flow to said battery means corresponding to battery charge rates greater than C/20 but less than C/5 where C represents the rated capacity of said battery means.

3. In a battery conditioning system according to claim 2, said rechargeable battery means comprising nickel-cadmium rechargeable battery means having a rated capacity of about two ampere-hours.

4. In a battery conditioning system according to claim 1, said rechargeable battery means comprising nickel-cadmium rechargeable battery means.

5. In a battery conditioning system according to claim 1, said computer means automatically controlling said current control means in response to said one of said measures of battery temperature so as to avoid extended overcharging of the rechargeable battery means at a rate exceeding rated capacity divided by twenty.

6. In a battery conditioning system according to claim 1, said computer means automatically operating in response to said one of said measures representative of said relatively low value of battery temperature so as to avoid substantial extended overcharging of the battery means at said relatively low value of battery temperature while providing respective progressively increased values of overcharge current for said others of said measures of battery temperature representing said respective different higher values of battery temperature over a substantial range lying above said relatively low value of battery temperature.

7. In a battery conditioning system according to claim 6, said battery means comprising nickel-cadmium battery means, and said computer means being automatically operative in response to said others of said measures of battery temperature to supply overcharge current values as a function of battery temperature between capacity divided by approximately twenty and capacity divided by approximately five.

8. In a battery conditioning system according to claim 1, said computer means automatically operating in response to said measures of battery temperature to provide respective successively increased rates of current flow to said battery means such that overcharge current is increased by a factor of at least four for the highest of the respective different higher values of battery temperature in comparison to said relatively low rate of current flow.

9. In a battery conditioning system according to claim 8, said battery means comprising a nickel-cadmium battery means.

10. In a battery conditioning system according to claim 1, said computer means automatically determining whether said battery means is in an overcharge condition, and when said battery means is not in overcharge condition selecting from a schedule of still higher rates of current flow to said battery means as a function of said measures of battery temperature, said still higher rates of current flow being respectively higher than overcharge of said battery means.

11. In a battery conditioning system according to claim 10, said computer means in determining whether said battery means is in said overcharge condition applying said relatively low rate of current flow for said relatively low value of battery temperature until such time as said one of said measures of battery temperature at least approximates ambient temperature.

12. In a battery conditioning system according to claim 10, said computer means in determining whether said battery means is in said overcharge condition applying said higher rates of current flow for said respective different higher values of battery temperature until such time as said one of said measures of battery temperature at least approximates the ambient temperature.

13. In a battery conditioning system according to claim 1, said computer means automatically comparing said measures of battery temperature with the ambient temperature, and when said battery temperature is not substantially less than the ambient temperature, applying a rate of current flow to said battery means as a function of said measures of battery temperature which is substantially higher than the respective rates of current flow as a function of said measures of battery temperature which are selected by said computer means during overcharge of said battery means.

14. In a battery conditioning system according to claim 1, said computer means having stored tables of suitable rates of current flow to said battery means as a function of said measures of battery temperature during overcharge of said battery means comprising said relatively low rate of current flow and said multiplicity of different higher rates of current flow.

15. In a battery conditioning system according to claim 13, said computer means having stored tables of suitable rates oi current flow to said battery means as a function of said measures of battery temperature during overcharge of said battery means comprising said relatively low rate of current flow and said multiplicity of different higher rates of current flow.

16. In a battery conditioning system according to claim 10, said computer means having stored tables of suitable rates of current flow to said battery means as a function of said measures of battery temperature during overcharge of said battery means comprising said relatively low rate of current flow and said multiplicity of different higher rates of current flow.

17. In a battery charging system,

(a) rechargeable battery means,

(b) external terminals of opposite polarity for the rechargeable

battery means,

(c) external circuit means between said rechargeable battery means and said external terminals of opposite polarity, said external circuit means having essentially negligible ohmic resistance and connecting said external terminals of opposite polarity with said battery means,

(d) load means at a load side of said external terminals, said external terminals having said load means connected there across at the load side of said external terminals such that said battery means supplies load current to said load means via said external circuit means with minimized ohmic loss at the battery side of said terminals, and

(e) automatically operating programmed system means comprising

(el) automatically operating processing means coupled with said external terminals for reading battery terminal voltage, and for increasing charging current to said battery means in successive steps to determine any load current being supplied to load means, and

(e2) automatically operating control means operating to apply substantially maximum charging current to said battery means consistent with avoiding substantial detriment to the operating life thereof while additionally supplying any required load current.

18. In a battery charging system according to claim 17, said automatically operating programmed system means comprising said automatically operating control means reading battery temperature and essentially supplying to said external terminals only the required load current so long as battery temperature exceeds a given upper limit temperature value.

19. In a battery charging system according to claim 17, said automatically operating control means insuring that battery temperature is above a selected minimum temperature value before applying said substantially maximum charging current to said battery means.

20. In a battery charging system according to claim 18, said automatically operating control means determining that battery temperature is within a given temperature range below said given upper limit temperature value, and then applying an excess overcharge current to said battery means which exceeds a substained overcharge rating of the battery means while limiting the time of application of said excess overcharge current to a time sufficient to detect the charge condition of the battery means without substantial detriment to the operating life thereof.

21. In a battery charging system according to claim 20, said automatically operating control means after detection of an overcharge condition of the battery means reducing overcharge current to a value according to said sustained overcharge rating of said battery means.

22. In a battery charging system according to claim 17, said automatically operating control means having means for automatically identifying a sustained overcharge current rating for said battery means.

23. In a battery charging system according to claim 17, said automatically operating control means insuring that battery temperature is above a selected minimum temperature value before applying said substantially maximum charging current to said battery means.

24. In a battery charging system according to claim 17, said automatically operating control means determining that battery temperature is within a given temperature range below a given upper limit temperature value, and then applying an excess overcharge current to said battery means which exceeds a sustained overcharge rating of the battery means while limiting the time of application of said excess overcharge current to a time sufficient to detect the charge condition of the battery means without substantial detriment to the operating life thereof.

25. In a battery charging system according to claim 24, said automatically operating control means after detection of an overcharge condition of the battery means reducing overcharge current to a value according to said sustained overcharge rating of said battery means.

26. In a battery charging system according to claim 17, said automatically operating control means having means for automatically identifying a sustained overcharge current rating for said battery means, and automatically supply an overcharge current according to said sustained overcharge rating to said battery means when said battery means has attained an overcharge condition.

27. In a battery charging system,

(a) rechargeable battery means,

(b) external terminals of opposite polarity for the rechargeable battery means,

(c) external circuit means between said rechargeable battery means and said external terminals of opposite polarity, said external circuit means connecting said external terminals of opposite polarity with said battery means,

(d) load means at a load side of said external terminals having said load means connected there across at the load side of said external terminals such that said battery means supplies load current to said load means via said external circuit means at the battery side of the said terminals, and

(e) automatically operating programmed system means comprising automatically operating control means operating to apply substantially maximum charging current to said battery means consistent with avoiding substantial detriment to the operating life thereof,

(f) said automatically operating control means having means for automatically identifying a sustained overcharge current rating for said battery means, and automatically supplying an overcharge current according to said sustained overcharge rating to said battery means when said battery means has attained an overcharge condition.

28. In a battery charging system according to claim 27, said automatically operating system means comprising said automatically operating control means reading battery temperature and essentially supplying to said external terminals only any required load current so long as battery temperature exceeds a given upper limit temperature value.

29. In a battery charging system according to claim 27, said automatically operating control means insuring that battery temperature is above a selected minimum temperature value before applying said substantially maximum charging current to said battery means.

30. In a battery charging system according to claim 27, said automatically operating control means determining that battery temperature is within a given temperature range below a given upper limit temperature value, and then applying an excess overcharge current to said battery means which exceeds the sustained overcharge rating of the battery means while limiting the time of application of said excess overcharge current to a time sufficient to detect the charge condition of the battery means without substantial detriment to the operating life thereof.

31. In a battery charging system according to claim 30, said automatically operating control means after detection of an overcharge condition of the battery means reducing overcharge current to a value according to said sustained overcharge rating of said battery means.

32. In a battery charging system,

(a) rechargeable battery means,

(b) external terminals of opposite polarity for the rechargeable battery means,

(c) external circuit means between said rechargeable battery means and said external terminals of opposite polarity, said external circuit means connecting said external terminals of opposite polarity with said battery means,

(d) load means at a load side of external terminals, said external terminals having said load means connected there across at the load side of said external terminals such that said battery means supplies load current to said load means via said external circuit means at the battery side of said terminals, and

(e) automatically operating programmed system means comprising automatically operating control means operating to apply substantially maximum charging current to said battery means consistent with avoiding substantial detriment to the operating life thereof,

(f) said automatically operating control means determining that battery temperature is within a given temperature range below a given upper limit temperature value, and then applying an excess overcharge current to said battery means which exceeds a sustained overcharge rating of the battery means while limiting the time of application of said excess overcharge current to a time sufficient to detect the charge condition of the battery means without substantial detriment to the operating life thereof.

33. In a battery charging system according to claim 32, said automatically operating control means after detection of an overcharge condition of the battery means reducing overcharge current to a value according to the sustained overcharge rating of said battery means.

34. In a battery charging system according to claim 32, said automatically operating control means having means for automatically identifying the sustained overcharge current rating for said battery means.

35. In a battery charging system according to claim 32, said automatically operating system means comprising said automatically operating control means reading battery temperature and essentially supplying to said external terminals only any required load current so long as battery temperature exceeds a given upper limit temperature value.

36. In a battery charging system according to claim 32, said automatically operating control means insuring that battery temperature is above a selected minimum temperature value before applying said substantially maximum charging current to said battery means.

37. The method of charging a battery pack comprising

(a) applying a charge increment to a rechargeable battery means,

(b) measuring a parameter sensitive to accumulation of charge by the battery means,

(c) repeating steps (a) and (b) as necessary to effect a determination of any load current being supplied by the battery means, and

(d) initiating a battery charging operation by supplying to the battery means a charging current taking account of any load current as determined by step (c) while enabling connections of minimum ohmic resistance between the battery means and the load.

38. Apparatus for charging a battery means, said apparatus comprising

(a) operating means for automatically obtaining measures of ambient temperature and of battery temperature of the battery means,

(b) said operating means automatically comparing the measures of the ambient temperature and said battery temperature, and when said measures show that said battery temperature is not substantially less than the ambient temperature, automatically applying current to the battery means of a substantial overcharge magnitude greater than a sustainable overcharge current, but of a limited duration such as to avoid substantial detriment to the useful life of the battery means even when in overcharged condition,

(c) said operating means repeatedly automatically obtaining said measures of the battery temperature and sensing any change in said measures of the battery temperature which is distinctive of the overcharge condition of the battery means so as to automatically determine whether or not the battery means is in overcharge condition, and

(d) means automatically applying a relatively high charge rate to said battery means while the battery means is not in the overcharge condition, and applying a relatively lower charge rate to said battery means when the battery means is in the overcharge condition.

39. Apparatus according to claim 38 with said operating means automatically comparing the measures of the battery temperature of said battery means and the ambient temperature, and if said measures show that the battery temperature is sufficiently lower than the ambient temperature that battery temperature will increase at a substantial rate due to ambient temperature higher than said battery temperature, delaying the application of said current of said substantial overcharge magnitude until said measures show that the battery temperature is approximately equal to said ambient temperature.

40. Apparatus according to claim 39, with said operating means automatically applying a current substantially less than said substantial overcharge magnitude to said battery means so as to increase said battery temperature before applying said current of said substantial overcharge magnitude, when said battery temperature is initially substantially lower than the ambient temperature.

41. A method of charging a battery means, said method comprising

(a) insuring that battery temperature of the battery means is not substantially less than the ambient temperature, and that the battery means will exhibit a substantially greater increase in said battery temperature when subjected to current of a substantial overcharge magnitude when it is in an overcharged condition than when it is not in said overcharged condition,

(b) automatically applying current to the battery means of said substantial overcharge magnitude, but of a limited duration such as to avoid substantial detriment to the useful life of the battery means even when in said overcharged condition,

(c) automatically measuring said battery temperature and sensing any change of the battery temperature due to step (b) which is distinctive of said overcharged condition of the battery means so as to automatically determine whether or not the battery means is in said overcharged condition, and

(d) automatically according to the result of step (c), applying a relatively high charge rate to said battery means while the battery means is not in said overcharged condition, and applying a relatively lower charge rate to said battery means when the battery means is in said overcharged condition.

42. The method of charging according to claim 41 with step (a) comprising

(a1) automatically comparing said battery temperature of said battery means with the ambient temperature and if said battery temperature is sufficiently lower than the ambient temperature so that it will increase at a substantial rate due to a higher ambient temperature than said battery temperature, delaying the application of said current of said substantial overcharge magnitude until the battery temperature is more nearly equal to the ambient temperature.

43. The method of charging according to claim 42, with step (a) further comprising

(a2) if step (a1) shows said higher ambient temperature, automatically applying a current to the battery means substantially less than said substantial overcharge magnitude so as to increase the battery temperature.

44. The method of charging according to claim 43 with step (a) additionally comprising

(a3) intermittently repeating step (a1) until said battery temperature is sufficiently high to enable the sensing of said overcharged condition by means of steps (b) and (c).

45. In a battery conditioning system,

(a) rechargeable battery means for supplying operating current during portable operation so as to become progressively discharged as a result,

(b) battery conditioning system means for coupling with said rechargeable battery means for supplying current to said rechargeable battery means during a battery conditioning cycle, after a period of portable operation,

(c) said battery conditioning system means comprising computer means having input means for receiving measures of battery and ambient temperature at successive times during the battery conditioning cycle, and

(d) current control means for coupling with said rechargeable battery means for controlling a current flow rate to the rechargeable battery means during the battery conditioning cycle,

(e) said computer means having output means coupled with said current control means for varying the current flow rate to said rechargeable battery means during the battery conditioning cycle as a function of the battery temperature as monitored by said computer means,

(f) wherein said computer means senses a differential between the ambient temperature and the battery temperature to insure a battery temperature rise will be essentially a function of an overcharge condition of the battery means as substantial current flow rates are supplied to the battery means during the battery conditioning cycle,

(g) said computer means, including programming, and including connection means for obtaining a measure of battery voltage of the battery means from a battery voltage measuring means and automatically operating to provide respective successively increased values of the current flow rate to compensate for battery load, until such time as the battery voltage has stabilized, and maintaining the current flow rate which compensates for the battery load until the battery temperature has increased to a selected temperature value suited to fast charging operation.

46. In a battery conditioning system according to claim 45, said battery means comprising a nickel-cadmium battery means wherein the current supplied to the battery means becomes overcharge current when most of the supplied current causes generation of oxygen gas.

47. A method of charging a battery means having a temperature characteristic when subject to overcharge current which exhibits a rising temperature as a function of overcharge current duration, said method comprising:

(a) insuring that the battery means has a state such that its temperature will not increase at a substantial rate due to a higher ambient temperature, and that the battery means will exhibit a substantially greater increase in battery temperature when subjected to the overcharge current than when subjected to a charging current when it is not overcharged, by monitoring both absolute temperature of the battery means and relative temperature between the battery means and ambient temperature, and automatically maintaining the battery temperature of the battery means within absolute and relative limits,

(b) automatically applying non-static, non-preset charging current at a charge at any stage of recharging to the battery means of a substantial magnitude, but measuring the battery temperature within a time interval after applying the charging current such as to avoid substantial detriment to useful life of the battery means prior to such measurement,

(c) automatically sensing any change of the battery temperature which is distinctive of an overcharge condition of the battery means so as to automatically determine whether or not the battery means is in the overcharge condition, and

(d) automatically according to the result of step (c), applying a relatively high charge rate as a function of the battery temperature to said battery means while the battery means is sensed not to be in the overcharge condition, and applying a relatively lower charge rate to said battery means when the battery means is in the overcharge condition, and in each case selecting the charge rate so as to avoid substantial detriment to the useful life of the battery means,

(e) measuring the ambient temperature and, after the battery means has reached the overcharge condition, the overcharge current flow rate is automatically adjusted according to the differential between the battery temperature and the ambient temperature, so as to maintain the battery means substantially in a fully charged condition.

48. The method of charging according to claim 47, where

(e1) step (e) comprises applying the overcharge current according to a safe overcharge value as a function of the battery temperature, where the battery temperature does not substantially exceed the ambient temperature.

49. The method of charging according to claim 48,

(e2) step (e) further comprises applying the overcharge current flow rate at a rate not substantially exceeding battery load current where the battery temperature substantially exceeds the ambient temperature.

50. The method of charging according to claim 49 with step

(e) comprising selecting between steps (e1) and (e2) in dependence upon whether the battery temperature exceeds the ambient temperature by a value of about eight degrees Celsius.

51. A method of charging a battery means which may have a load requiring current during charging operation, said method comprising

(a) measuring battery voltage to produce a measured value and applying moderate non-static, non-present charging current at any stage of recharging to the battery means,

(b) measuring battery temperature at successive times and determining whether the battery temperature is substantially outside a given temperature range before applying substantial charging current to the battery means, and if it is outside such temperature range,

(c) sensing whether the applied moderate charging current has increased the battery voltage, and

(d) increasing the charging current to the battery means a small increment where the battery voltage has not substantially increased within a given time interval.

52. In a method according to claim 51, repeating steps (b), (c) and (d) until such time as the battery voltage corresponds to the measured value, or the battery temperature is within said given temperature range.

53. In a method according to claim 51, repeating steps (b) and (c), and where the battery voltage has increased above the measured value, decreasing the moderate charging current to the battery means by a small increment, so that the battery voltage is maintained in the vicinity of the measured value until such time as the battery temperature is within the given temperature range, whereupon the substantial charging current may be applied.

54. A battery recharging system for recharging to and maintaining at maximum capacity a rechargeable battery comprising:

rechargeable battery means for providing a stored electric potential;

current control means for providing an adjustable recharging current to the battery means during a recharging period;

computer means for controlling the current control means and monitoring temperature of the battery means and ambient temperature;

input means included with the computer means for receiving successive measurements of the battery temperature and the ambient temperature at least during the recharging period;

output means included with the computer means for providing control signals to the current control means during the recharging period;

overcharge detection means associated with the computer means for automatically sensing a change of the battery temperature which is distinctive of an overcharge condition of the battery means; and

charge rate means associated with the computer means for automatically applying a relatively high charge rate of the recharging current, as a function of the battery temperature, to said battery means while the battery means is sensed not to be in the overcharge condition, and for applying a relatively lower charge rate of the recharging current to said battery means when the battery means is in the overcharge condition, and in each case selecting the charge rate so as to avoid substantial detriment to useful life of the battery means, said charge rate means dynamically and automatically adjusting the charging current as a function of the differential between the battery temperature and the ambient temperature to maintain the battery means in a substantially fully charged condition.

55. The system of claim 54 including switching means associated with the computer means for immediately changing the recharging current from the relatively high charge rate to the relatively lower charge rate upon detection of the overcharge condition.

56. A battery recharging system for recharging to and maintaining at maximum capacity a rechargeable battery comprising:

rechargeable battery means for providing stored electric potential for use by a load;

current control means for providing an adjustable recharging current to the battery means during a recharging period;

computer means for controlling the current control means and monitoring the battery means for an overcharge condition;

the computer means including input means for receiving repeated measurements of battery temperature and ambient temperature and output means for providing control signals to the current control means;

overcharge detection means associated with the computer means for automatically sensing any change of the battery temperature which is distinctive of the overcharge condition of the battery means so as to automatically determine whether or not the battery means is in the overcharge condition; and

charge rate means associated with the computer means for automatically and dynamically adjusting the recharging current to the battery means according to any ongoing differential between the battery temperature and the ambient temperature when the battery means has been sensed to have reached the overcharge condition, said charge rate means providing the battery means with a relatively low but variable rate of the recharging current to maintain the battery means substantially in a fully charged condition but to avoid substantial detriment to useful life of the battery means.

57. A method of charging a rechargeable battery means comprising:

measuring the difference between battery temperature of the battery means and ambient temperature;

applying a relatively low rate of charge current to the battery means if the battery temperature and the ambient temperature are not substantially close, to stabilize any temperature difference between the battery and ambient temperatures and prevent discharge of the battery means;

measuring the battery temperature to detect if the battery temperature is within a given temperature range to determine if the battery means is within an optimal charging temperature range;

applying a relatively moderate rate of charge current to the battery means if the battery temperature is outside the optimal charging temperature range, the relatively moderate rate dynamically varying as a function of the battery temperature to bring the battery temperature within the optimal charging temperature range;

applying a relatively high rate of charge current to the battery means if the battery temperature is within the optimal charging temperature range, the relatively high rate dynamically varying as a function of the battery temperature, the rate of charge current always being selected so as to avoid substantial detriment to useful life of the battery means;

measuring the difference between the battery temperature and the ambient temperature to sense any change of the battery temperature distinctive of an overcharge condition for the battery means; and

applying the relatively low rate of charge current when the battery temperature is sensed to indicate an overcharge condition, the relatively low rate dynamically varying as a function of the battery temperature but always being selected so as to avoid substantial detriment to the useful life of the battery means.

58. A method for recharging a rechargeable battery means comprising:

measuring battery and ambient temperature at successive times;

stabilizing the battery means by causing any difference between the ambient temperature and the battery temperature to be substantially close;

causing the battery temperature to be within a given optimal charging temperature range by measuring the battery temperature, comparing the battery temperature with the given optimal charging temperature range, measuring battery voltage, and dynamically applying current at a variable charge rate determined as a function of the battery temperature and the battery voltage, if the battery temperature is outside the optimal charging temperature range to bring the battery temperature within the optimal charging temperature range prior to recharging;

dynamically applying a current to the battery at a relatively high variable charge rate once the battery temperature is within the optimal charging temperature range, the relatively high variable charge rate determined as a function of the difference between the battery temperature and the ambient temperature;

continuing to apply the relatively high variable charge rate for fast recharging of the battery means while repetitively measuring the battery temperature to sense any battery temperature change which is distinctive of an overcharge condition of the battery means; and

applying a relatively lower charge rate selected between a predetermined non-varying charge rate if the battery temperature exceeds the ambient temperature by a substantial amount, and a varying charge rate dynamically varying as a function of battery temperature if the battery temperature does not exceed the ambient temperature by a substantial amount, to maintain the battery means in a fully charged condition, but avoiding substantial detriment to useful life of the battery means.

59. A method for fast charging of a rechargeable battery which deters damage to the battery during charging and maintains the battery in a fully charged capacity after charging, comprising:

measuring battery and ambient temperatures at successive times;

measuring battery voltage;

preparing the battery for optimal charging by applying a relatively non-varying low charge rate to the battery if the ambient temperature and the battery temperature differ by a substantial amount, and by applying a relatively low but varying charge rate which dynamically various as a function of the battery temperature and the battery voltage if the battery temperature is outside a given optimal charging temperature range;

charging the battery at a relatively fast charge rate which dynamically varies as a function of the battery temperature once the battery is prepared for optimal charging;

continuously monitoring the battery temperature during application of the relatively fast charge rate to detect any increase of the battery temperature which indicates an overcharge condition of the battery; and

immediately switching the relatively fast charge rate to the relatively low charge rate upon detection of the overcharge condition, the relatively low charge rate dynamically varying as a function of the battery temperature to maintain the battery fully charged without substantial detriment to useful, life of the battery.