Battery pack having a processor controlled battery operating system

• US 5,691,621 A
• Filed: 06/07/1995
• Issued: 11/25/1997
• Est. Priority Date: 11/10/1994
• Status: Expired due to Fees

• Current Assignee: Microchip Technology Incorporated
• Original Assignee: Duracell Incorporated (Berkshire Hathaway Incorporated)
• Inventors: Phuoc, Duong Var, Friel, Daniel D., Hull, Matthew P., Taylor, Alwyn H., Wieczorek, Rudi, Zeising, Elmar, Hruska, Louis W.
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): Toatley, Jr., Gregory J.
• Application Number:
  US08/473,341
• Time in Patent Office: 902 Days
• Field of Search: 320/5, 320/19, 320/20, 320/22, 320/30, 320/35, 320/48, 324/426, 365/96, 365/106
• US Class Current: 320/134
• CPC Class Codes: G01R 31/396 Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
• CPC Class Codes: H01M 10/42 Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells H01M10/60 takes precedence
• 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 6/5011 for several cells simultaneously or successively
• 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 7/00047 with provisions for charging different types of batteries
• CPC Class Codes: H02J 9/061 for DC powered loads
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y10S 320/13 Fault detection

Abstract

A battery pack and a method of operating a battery system. The battery pack includes a rechargeable battery and a processor for monitoring the battery during charging and discharging. The processor receives data values representing the battery voltage, temperature and current, and the processor performs a series of calculations using those data values. In one of these calculations, the processor determines the actual full capacity of the battery. Preferably, the processor also keeps track of an uncertainty value that represents an uncertainty in the capacity of the battery; and the processor calculates the actual full capacity of the battery at the end of each discharge cycle if, at that time, the uncertainty value is less than a given percentage of a nominal full capacity of the battery.

Claims

1. A smart battery which provides electrical power and which reports predefined battery parameters to an external device having a power management system, said smart battery comprising:

(a) at least one rechargeable cell connected to a pair of terminals to provide electrical power to an external device during a discharge mode and to receive electrical power during a charge mode, as provided or determined by said remote device,

(b) a data bus for reporting predefined battery identification and charge parameters to the external device,

(c) an analog means for generating analog signals representative of battery voltage and current at said terminals, and an analog signal representative of battery temperature at said cell,

(d) a hybrid integrated circuit (Ic) having a microprocessor for receiving the analog signals and converting them to digital signals representative of battery voltage, current and temperature, and calculating actual charge parameters over time from said digital signals, said calculations including a capacity reset and an error calculation which is incremented after each partial charge and extinguished at each capacity reset;

(e) a data memory defined within said hybrid IC for storing said predefined battery identification and actual charge parameters, even when nominally fully discharged, said charge parameters including a cumulative error value,

(f) a bus controller defined within said hybrid IC for sending battery messages to said remote device over said data bus, said messages including said predefined battery identification and said actual charge parameters.

2. A battery pack comprising:

terminal means for connecting the battery pack to a battery powered device and to a battery recharger;

a battery including at least one rechargeable battery cell connected to the terminal means, said battery having

i) discharging periods for supplying electrical power to the battery powered device, and

ii) charging periods for receiving electrical power from the terminal means;

means to sense and to generate signals representing battery voltage, battery temperature or battery current;

a processor for receiving the signals representing battery voltage, battery temperature or battery current, and for performing a predefined series of calculations using said signals, wherein said predefined calculations include calculating an actual full capacity of the battery at the ends of at least selected ones of the discharging periods; and

a memory area for storing data values including at least values representing battery voltage, battery temperature and battery current.

3. A battery pack according to claim 2, wherein:

the processor maintains

i) an uncertainty value representing an uncertainty in the full capacity of the battery, and

ii) a nominal full capacity value representing a nominal full capacity of the battery;

after each end of the selected ones of the discharging periods, if the uncertainty value is less than a given percentage of the nominal full capacity value, then the processor calculates the actual full capacity of the battery.

4. A battery pack according to claim 2, wherein:

the processor includes means to determine a correction value; and

at the end of a given discharging period, when the processor calculates a new value for the actual full capacity value of the battery, the processor calculates said new value according to the equation

space="preserve" listing-type="equation">nCAP.sub.FC =oCAP.sub.FC +(oCAP.sub.FC)x-CAP.sub.REM

where;

nCAP_FC is the new value for the actual full capacity of the battery,

oCAP_FC is the most recently previously calculated value for the actual full capacity of the battery, x is the correction value determined by the processor, and

CAP_REM is the capacity of the battery at the end of the given charge-discharge cycle.

5. A battery pack according to claim 4, wherein the means to determine the correction value includes means to determine the correction value based on battery temperature and battery current.

6. A battery pack according to claim 5, wherein the means to determine the correction value includes:

a look-up table having a multitude of stored values; and

means to select one of said stored values based on the battery temperature and battery current.

7. A battery pack according to claim 3, wherein the predefined calculations further include calculating the uncertainty value at predetermined times.

8. A battery pack according to claim 7, wherein the uncertainty value is reset to zero at given times.

9. A battery pack according to claim 8, wherein:

the processor includes means to detect a plurality of predefined end of charge conditions during the charging periods, and to terminate each of the charging periods when one of said end of charge conditions is detected during said each of the changing periods; and

the processor resets the uncertainty value to zero when one of said end of charge conditions is detected.

10. A battery pack according to claim 8, wherein:

the processor includes means to detect a plurality of predefined end of discharge conditions during the discharging periods, and to terminate each of the discharging periods when one of said end of discharge conditions is detected during said each of the discharging periods; and

the processor resets the uncertainty value to zero when one of said end of discharge conditions is detected.

11. A battery pack according to claim 8, wherein:

the processor includes means to determine the accumulated amount of current conducted to the battery during each of the charging periods; and

when the uncertainty value is calculated during one of the charging periods, the calculated uncertainty value is based on the accumulated amount of current conducted to the battery during said one of the charging periods.

12. A battery according to claim 8, wherein:

the processor includes means to determine the accumulated amount of current discharged from the battery during each of the discharging periods; and

when the uncertainty value is calculated during one of the discharging periods, the calculated uncertainty value is based on the accumulated amount of current discharged from the battery during the said one of the discharging periods.

13. A method of operating a battery system having a rechargeable battery connected to a battery powered device, a processor and a memory area, the method comprising:

discharging the battery during discharging periods to power the battery powered device;

charging the battery during charging periods;

sensing, and generating signals representing, battery voltage, battery temperature and battery current;

storing data values in the memory area, said stored data values including at least values representing battery voltage, battery temperature and battery current; and

the processor performing predefined calculations using the signals representing battery voltage, battery temperature and battery current, including the step of calculating actual full capacity of the battery at the ends of at least selected ones of the discharging periods.

14. A method according to claim 13, wherein:

the step of performing predefined calculations further includes the steps of the processor

i) maintaining an uncertainty value representing an uncertainty in the full capacity of the battery, and

ii) maintaining a nominal full capacity value representing a nominal full capacity of the battery; and

the step of calculating the actual full capacity of the battery includes the step of, after each end of the selected ones of the discharging periods, calculating the actual full capacity of the battery if the uncertainty value is less than a given percentage of the nominal full capacity value.

15. A method according to claim 13, wherein:

the step of performing predefined calculations further includes the step of determining a correction value; and

the step of calculating the actual full capacity of the battery includes the step of

calculating a new value for the actual full capacity of the battery according to the equation

space="preserve" listing-type="equation">nCAP.sub.FC =oCAP.sub.FC +(oCAP.sub.FC)x-CAP.sub.REM

where

nCAP_FC is the new value for the actual full capacity of the battery,

oCAP_FC is the most recently previously calculated value for the actual full capacity of the battery,

x is the determined correction value, and

CAP_REM is the capacity of the battery at the time said new value is calculated.

16. A method according to claim 15, wherein the step of determining the correction value includes the step of determining the correction value based on battery temperature and battery current.

17. A method according to claim 16, wherein the memory area includes a look-up table having a multitude of stored values, and wherein the step of determining the correction value includes the step of selecting one of the values from the look-up table on the basis of the battery temperature and the battery current.

18. A method according to claim 15, wherein the step of determining the uncertainty value includes the step of calculating the uncertainty value at predefined times.

19. A method according to claim 18, wherein the step of determining the uncertainty value further includes the step of resetting the uncertainty value to zero at given times.

20. A method according to claim 19, wherein:

the method further includes the step of,

during each of the discharging periods, the processor detecting one of a plurality of predefined end of discharge conditions, and terminating the discharging period when said one of said end of discharge conditions is detected; and

the step of resetting the uncertainty value to zero includes the step of resetting the uncertainty value to zero when one of said end of discharge conditions is detected.

21. A method according to claim 19, wherein:

the step of calculating the uncertainty value includes the steps of

i) determining the accumulated amount of charge conducted to the battery during each of the charging periods, and

ii) when the uncertainty value is calculated during the charging period, calculating said uncertainty value on the basis of the accumulated amount of charge conducted to the battery during said charging period.

22. A method according to claim 19, wherein:

the step of calculating the uncertainty value includes the steps of

i) determining the accumulated amount of charge discharged from the battery during each of the discharging periods, and

ii) when the uncertainty value is calculated during one of the discharging periods, calculating said uncertainty value on the basis of the accumulated amount of charge discharged from the battery during said one of the discharging periods.

23. A battery pack comprising:

terminal means for connecting the battery pack to a battery powered device and to a battery recharger;

a battery including at least one rechargeable battery cell connected to the terminal means, said battery having

i) a discharge mode for supplying electrical power to the battery powered device, and

ii) a charge mode for receiving electrical power from the terminal means;

means to sense and to generate signals representing battery voltage, battery temperature, and battery current;

a memory area for storing data values including at least values representing battery voltage, battery temperature and battery current; and

a processor for receiving the signals representing battery voltage, battery temperature and battery current, and for performing predefined calculations using said signals, the processor including

i) means to calculate an uncertainty value, and

ii) means to calculate one of said stored data values at defined times if the uncertainty value is below a given level.

24. A battery pack according to claim 23, wherein the means to calculate one of said stored data values calculates said one of said stored data values at each of said defined times if and only if at said each of said defined times the uncertainty value is below the given level.

25. A battery pack according to claim 24, wherein the means to calculate the uncertainty value resets the uncertainty value to zero at predetermined times.

26. A battery pack according to claim 25, wherein the processor includes means to determine when said predetermined times occur.

27. A battery pack according to claim 25, wherein:

the battery has charge-discharge cycles, each of said cycles having a discharging portion and a charging portion;

the processor further includes means to detect a plurality of predefined end of discharge conditions during the discharging portion of each charge-discharge cycle, and to terminate the discharging portion of the charge-discharge cycle when one of said end of discharge condition is detected; and

the processor resets the uncertainty values to zero when one of said end of discharge condition is detected.

28. A method of operating a battery system having a rechargeable battery connected to a battery powered device, a processor and a memory area, the method comprising:

sensing, and generating signals representing, battery voltage, battery temperature and battery current;

storing data values in the memory area, said stored data values including at least values representing battery voltage, battery temperature and battery current; and

the processor performing predefined calculations using the signals representing battery voltage, battery temperature and battery current, including the steps of

i) calculating an uncertainty value, and

ii) calculating one of said stored data values at defined times if the uncertainty value is below a given level.

29. A method according to claim 28, wherein the step of calculating one of said stored data values includes the step of calculating said one of said stored data values at each of said defined times if and only if at said each of said defined times the uncertainty value is below the given level.

30. A method according to claim 28, wherein:

the battery has charge-discharge cycles, each of said cycles having a discharging portion and a charging portion;

in the discharging portion of each of said cycles, current is discharged from the battery;

in the charging portion of each of said cycles, current is conducted to the battery; and

the step of calculating the uncertainty value includes the steps of

i) in the discharging portion of each of said cycles, calculating an uncertainty in the accumulated amount of current conducted from the battery during the discharging portion of the cycle, and

ii) in the charging portion of each of said cycles, calculating an uncertainty in the accumulated amount of current discharged from the battery during the discharging portion of the cycle.