Fast battery charger

• US 5,493,199 A
• Filed: 10/06/1992
• Issued: 02/20/1996
• Est. Priority Date: 06/07/1982
• Status: Expired due to Term

• Current Assignee: Intermec Inc (Honeywell International Inc.)
• Original Assignee: Norand Corporation (Baker Hughes Company)
• Inventors: Koenck, Steven E., Miller, Phillip, Becker, Ronald D.
• Primary Examiner(s): Stephan, Steven L.
• Assistant Examiner(s): Ponomarenko, Nicholas
• Application Number:
  US07/957,470
• Time in Patent Office: 1,232 Days
• Field of Search: 320/35
• US Class Current: 320/106
• 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 7/0049 Detection of fully charged condition
• 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

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 automatically adjust to different levels 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 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 dynamic, charging current to said rechargeable battery means during at least a portion of 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 intervals 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 of current flow to said rechargeable battery means during a battery conditioning cycle as a function of battery temperature as monitored by said computer means without relying on measured battery voltage, including dynamically varying rate of current flow by successive relatively small incremental changes, as a function of battery temperature during said portion of the battery conditioning cycle to maximize efficiency of recharging,

(f) wherein said computer means senses a differential between ambient temperature and battery temperature to insure that 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 a battery conditioning cycle, the substantial current flow rates varying dynamically as a function of battery temperature.

2. In a battery conditioning system according to claim 1, said computer means adjusting said current control means during a battery conditioning operation so as to provide a moderate rate of current flow when the battery temperature is substantially greater than ambient temperature.

3. In a battery conditioning system according to claim 2, said rechargeable battery means comprising nickel-cadmium rechargeable battery means.

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 4, said computer means including programming, automatically controlling said current control means so as to avoid extended overcharging of the rechargeable battery means when the differential between ambient temperature and battery temperature is greater than ten degrees celsius.

6. In a battery conditioning system according to claim 1, said computer means including programming, automatically operating so as to avoid substantial extended overcharging of the battery means at extremes in the differential between ambient temperature and battery temperature while providing respective progressively increased values of overcharge current for respective progressively increased values of battery temperature over a substantial range after the differential between ambient temperature and battery temperature has been reduced.

7. In a battery conditioning system according to claim 6, said battery means comprising nickel-cadmium battery means, and said computer means including programming being automatically operative to supply a current flow rate to the battery means not substantially exceeding an overcharge rate for the battery means until such time as battery temperature is generally equal to ambient temperature.

8. The battery conditioning system of claim 1, said computer means further comprising memory means for storing predetermined values of rate of current flow correlated to the specific battery means for incremental changes in measured temperature, wherein said current control means varies the rate of current flow to said rechargeable battery means with reference to the predetermined values.

9. 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:

measuring battery temperature;

sensing any change in battery temperature which is distinctive of an overcharge condition of the battery means to automatically determine, without relying on measured battery voltaqe, whether or not the battery means is in the overcharge condition;

measuring ambient temperature at successive times;

applying a relatively high charge rate to said battery means while the battery means is sensed not to be in the overcharge condition, the relatively high charge rate being dynamically adjusted by successive relatively small incremental changes as a function of battery temperature;

comparing battery and ambient temperatures; and

applying a relatively lower charge rate to said battery means when the battery means is sensed to be in the overcharge condition, the relatively lower charge rate being dynamically adjusted by successive relatively small incremental changes as a function of the differential between battery temperature and ambient temperature to maintain the battery means substantially in a fully charged condition but to avoid substantial detriment to the useful life of the battery means.

10. The method of claim 9 further comprising the steps of:

pre-selecting a set of relatively high charge rates for given temperatures for a given battery type and capacity;

pre-selecting a set of relatively lower charge rates for given temperatures for a given battery type and capacity;

wherein said relatively high charge rate is applied from the set of relatively high charge rates; and

said relatively lower charge rates are applied from the set of relatively lower charge rates.

11. 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:

measuring battery temperature at intervals;

sensing any change in battery temperature which is distinctive of an overcharge condition of the battery means to automatically determine whether or not the battery means is in the overcharge condition without relying on measured battery voltage;

measuring ambient temperature;

comparing battery and ambient temperature; and

applying a relatively lower charge rate to said battery means when the battery means is sensed to be in the overcharge condition, the relatively lower charge rate being dynamically adjusted by successively small incremental changes as a function of the differential between battery temperature and ambient temperature to maintain the battery means substantially in a fully charged condition but to avoid substantial detriment to the useful life of the battery means.

12. The method of claim 11 wherein the conversion from a relatively high charge rate to a relatively low charge rate is accomplished quickly to avoid detriment to the useful life of the battery means.

13. The method of claim 11 further comprising the step of pre-selecting a set of relatively lower charge rates for given temperatures for a given battery type and capacity wherein said relatively lower charge rate is applied from the set of relatively lower charge rates.

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

determining when the battery is in an optimal condition for charging by measuring battery temperature, ambient temperature, and battery voltage to characterize current drain caused by battery load if any, and causing battery temperature to be in a given temperature range;

presenting current to the battery at a relatively fast charge rate to quickly recharge the battery;

monitoring battery temperature at closely repeated intervals to detect any increase of battery temperature which indicates an overcharged condition of the battery without relying on measured battery voltage;

immediately converting the fast charge rate to a relatively lower charge rate upon detection of the overcharge condition; and

monitoring battery temperature during overcharge condition and dynamically varying the lower charge rate as a function of battery temperature to provide an optimal charge rate which compensates for any battery load to maintain the battery in a fully charge condition while avoiding substantial detriment to the useful life of the battery.

15. 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 temperature and ambient at successive time 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 of current flow to said rechargeable battery means during a battery conditioning cycle as a function of battery temperature as monitored by said computer means without relying on measured battery voltage,

(f) wherein said computer means senses a differential between ambient temperature and battery temperature to insure that 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 a battery conditioning cycle, said computer means including programming, and including connection means for obtaining a measure of the voltage of the battery means from a battery voltage measuring means for characterizing current drain caused by battery load, if any, and automatically operating to provide respective successively increased values of current flow rate to compensate for battery load, until such time as battery voltage has stabilized, and maintaining a current flow rate which compensates for battery load until the battery temperature has increased to a elected temperature value suited to fast charging operation.

16. The battery conditioning system of claim 15 wherein said battery means comprises a nickel-cadmium battery means wherein current supplied to the battery means becomes overcharge current when most of the supplied charge causes generation of oxygen gas.

17. A battery recharging system for recharging and maintaining a rechargeable battery to maximum capacity 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 battery temperature and ambient temperature at least during the recharging periods;

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

overcharge detection means associated with the computer means for automatically sensing a change of battery temperature which is distinctive of an overcharge condition of the battery means by comparison in the computer means of the successive measurements of battery temperature and ambient temperature communicated to the computer means and without relying on measured battery voltage.

18. The battery recharging system of claim 17 further comprising temperature monitoring means for measuring battery temperature and ambient temperature, including means for operative connection to the input means.

19. The battery recharging system of claim 17 further comprising a portable housing means for containing components of the battery recharging system.

20. The battery recharging system of claim 17 further comprising:

memory means for storing predetermined values of rate of the recharging current correlated to the specific battery means for incremental changes in measured temperature; and

wherein said current control means provides a relatively low recharging current according to said predetermined values.

21. 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:

supplying charging current at a charge rate to the battery means;

monitoring temperature of battery means at spaced intervals;

monitoring ambient temperature at or near the battery means;

determining an overcharge condition of the battery means by detecting a difference between battery temperature and ambient temperature of a magnitude distinctive of an overcharge condition of the battery means without relying on measured battery voltage; and

supplying a relatively lower charge rate when an overcharge condition has been established;

so that protection of the overcharge condition is made independent of any measurement of battery voltage, load, or battery current.

22. The method of claim 21 wherein the steps of monitoring battery temperature and ambient temperature, and determining an overcharge condition are applied to a battery means in a portable, hand-held device.

23. The method of claim of 21 further comprising controlling charge rate to the battery means as a function of battery temperature.

24. The method of claim 21 further comprising controlling charge rate to the battery as a function of whether the battery means is in an overcharge condition.

25. The method of claim 21 further comprising controlling charge rate to the battery means as a function of battery temperature and whether the battery means is in an overcharge condition.

26. The method of claim 21 further comprising controlling charge rate of charging current to the battery means after sensing of the overcharge condition by adjusting the charge rate as a function of battery temperature.

27. The method of claim of 21 further comprising monitoring an initial charge state of the battery means.

28. The method of claim 27 wherein the initial charge state of the battery means is detected by measuring battery voltage.

29. The method of claim of 27 wherein the initial charge state of the battery means is detected by measuring battery temperature.

30. The method of claim 27 further comprising controlling charge rate of recharging current to the battery means after detecting an initial charge state by selecting charge rate as a function of battery temperature.

31. The method of claim of 30 wherein the selection of charge rate is accomplished independently of measurement and detection of current flow through the battery means.

32. The method of claim 21 further comprising the step of:

pre-selecting a set of relatively lower charge rates for a given temperature for a given battery type and capacity; and

wherein said relatively lower charge rate is supplied from the set of relatively lower charge rates.

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

measuring battery temperature at spaced intervals;

measuring ambient temperature;

comparing battery and ambient temperature; and

applying a relatively moderate charge rate of recharging current to the battery means, the charge rate being determined between at least two distinct levels as a function of the difference between battery temperature and ambient temperature but without relying on measured battery voltage;

the relatively moderate charging current being dynamically adjusted by successive relatively small incremental changes as a function of a comparison of battery temperature, ambient temperature, and the rate of change of battery temperature.

34. The method of claim 33 wherein the battery means has characteristics which can be stored in a battery identification means which relates to charging parameters of the battery means.

35. The method of claim 34 wherein the charge rate is determined additionally by battery identification.

36. The method of claim 33 wherein the charge rate is additionally determined by current to the load.

37. The method of claim 33 wherein the battery means has a range of safe overcharging current and the charge rate is additionally determined by the range of safe overcharging current.

38. The method of claim 33 wherein the relatively moderate charging current is dynamically adjusted as a function of a comparison of battery temperature and ambient temperature.

39. The method of claim 33 wherein the dynamic adjustment of relatively moderate recharging current is carried on with a periodic monitoring of battery temperature and ambient temperature.

40. The method of claim 39 wherein the dynamic adjustment occurs between at least two discrete current levels.

41. The method of claim 39 wherein the dynamic adjustment occurs between a plurality of incremental current levels.

42. 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, the method comprising:

monitoring temperature of the battery means at intervals;

monitoring ambient temperature at or near the battery means;

monitoring rate of change of the temperature of the battery means;

comparing battery temperature and ambient temperature; and

determining an overcharge condition of the battery means by detecting a rise in temperature of said battery means of a predetermined rate when said battery means temperature and said ambient temperature are within a predetermined range of one another when charging is initiated by application of charging current to the battery means but without relying on measured battery voltaqe so that protection of the battery means in an overcharged condition is made independent of any measurement of battery voltage, load, or battery current.

43. A method of charging a battery prior to its reaching an overcharge condition, which comprises:

applying recharging current to the battery such that battery temperature may increase as a result;

measuring battery temperature during application of such recharging current at time intervals not exceeding a time interval of the order of one minute; and

incrementally adjusting the recharging current as a function of such battery temperature measurement so as to closely follow a schedule of maximum charge rates as a function of battery temperature which applies prior to the battery reaching the overcharge condition but without relying on measured battery voltage.

44. The method according to claim 43 wherein the schedule of maximum charge rate as a function of battery temperature provides changing recharging current values for successive changes in battery temperature of the order of two degrees Celsius.

45. A method of charging a battery once it has reached an overcharge condition comprising:

applying recharging current to the battery such that battery temperature may change as a result;

measuring battery temperature during application of such recharging current at time intervals not exceeding a time interval of the order of one minute; and

incrementally adjusting the recharging current as a function of such battery temperature measurements so as to closely follow a schedule of maximum charge rates as a function of battery temperature which applies after the overcharge condition has been reached but relying on measured battery voltage.

46. The method according to claim 45 wherein the schedule of maximum charge rate as a function of battery temperature provides charging recharging current valves for successive charges in battery temperature of the order of two degrees Celsius.

47. The method of charging a battery means which may have a load requiring current during charging operation, said method comprising:

(a) measuring battery voltage to characterize current drain caused by battery load, if any, and applying moderate non-static, non-preset charging current at any stage of recharging to the battery means,

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

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

(d) increasing current to the battery means without relying on measured battery voltage by a small increment where battery voltage has not substantially increased within a given time interval.

48. The method of claim 47 further comprising dynamically adjusting current to the battery means until the battery means temperature is within a given temperature range.

49. The method of claim 48 wherein the dynamic adjustment of current is between a plurality of discrete current levels.

50. The method of claim 49 wherein the plurality of discrete levels differ by increments over a range of current values.

51. The method of claim 47 wherein the increased current is taken from a set of current values between relatively low and relatively high current values.

52. The method of claim 51 wherein the relatively low current values are selected when battery temperature is relatively low compared to ambient temperature.

53. The method of claim 51 where the current values are relatively high when battery temperature is relatively high compared to ambient temperature.