Battery monitoring and charging control unit

• US 5,563,496 A
• Filed: 09/14/1994
• Issued: 10/08/1996
• Est. Priority Date: 12/11/1990
• Status: Expired due to Fees

• Current Assignee: SPAN Incorporated
• Original Assignee: SPAN Incorporated
• Inventors: McClure, Malcolm S.
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): TOATLEY, GREGORY J
• Application Number:
  US08/306,121
• Time in Patent Office: 755 Days
• Field of Search: 320/31, 320/32, 320/22-24, 320/37-40, 320/43, 320/44, 320/48, 324/426-7, 324/433
• US Class Current: 320/128
• CPC Class Codes: H02J 2207/20 Charging or discharging characterised by the power electronics converter
• CPC Class Codes: H02J 7/007184 in response to battery voltage gradient
• CPC Class Codes: H02J 7/02 for charging batteries from ac mains by converters
• CPC Class Codes: H02M 3/155 using semiconductor devices only
• CPC Class Codes: H02M 7/217 using semiconductor devices only

Abstract

A unit that can be a tiny module within a battery pack includes a microprocessor operating through onboard sensors and read circuitry to monitor battery current, voltage and temperature and to develop fast charge termination control data. Various termination schemes are available including negative delta V, dT/dt, dV/dt, absolute temperature, absolute voltage, and override timer. The microprocessor also operates to develop state of charge, percentage of capacity charge and other status data, to store such data along with setup and calibration data, in an EEPROM, to report data to a host periodically or when polled to and to operate automatically or at a user'"'"'s request to initially perform and update a calibration as to actual battery capacity. During times when the pack is idle, the unit automatically reverts to a low-power mode in which measuring circuitry is deenergized but during such times, it operates periodically to compensate for self-discharge as a function of temperature. In the read circuitry, a ramp generator generates a linear ramp voltage that is compared with voltages proportional to battery voltage, supply voltage, battery current and temperature, using comparators connected to pins of a common port of the microprocessor and using a mask to obtain all readings from a single generation of the ramp. Voltage dividers of the read circuitry are so arranged as to permit accurate readings of current in either direction and to operate in a bridge configuration to obtain normalized measurements independent of ramp slope. Dynamic correction of readings and other features are also provided.

Claims

1. A monitoring unit for monitoring the condition of charge of a battery, comprising:

processor means operable during flow of charge current to said battery and discharge current from said battery for performing periodic read and processing operations, each read operation including producing a battery current reading corresponding to net current flowing to said battery, and each processing operation including producing an output reading from said battery current, and adding said output reading to a stored accumulated charge value indicating the condition of charge of said battery, said producing of said output reading from said battery current reading including adjusting said battery current reading as function of operating conditions to produce said output current reading as a function of net change in energy stored in said battery since a last preceding read operation.

2. A monitoring unit as defined in claim 1, said adjusting of said battery current reading as a function of operating conditions including adjusting said battery current reading as a function of said stored accumulated charge value when said battery current reading has a positive value during charging of said battery.

3. A monitoring unit as defined in claim 2, including means for supplying a charge capacity value for said battery, said adjusting of said battery current reading as a function of said stored accumulated charge value being performed by determining the product of said battery current reading and a charge capacity factor which is a function of the ratio of said stored accumulated charge value to said charge capacity value.

4. A monitoring unit as defined in claim 3, means storing a table of said charge capacity factors in memory for access according to said ratio of said stored accumulated charge value to said charge capacity value.

5. A monitoring unit as defined in claim 3, said processing means being operable in a calibrating mode after charging of said battery to a full charge condition and during a subsequent discharge of said battery to a certain discharge condition to determine a resultant decrease in said accumulated charge value and to then adjust said charge capacity value as a function of said decrease in said accumulated charge value.

6. A monitoring unit as defined in claim 1, each of said read operations including producing a temperature reading, and said adjusting of said battery current reading as a function of operating conditions including operating when said battery current reading has a positive value during charging of said battery to adjust said battery current reading as a function of said temperature reading.

7. A monitoring unit as defined in claim 6, means storing a table of temperature factors in memory for access according to said temperature reading, said adjusting of said battery current reading as a function of said temperature reading being performed by determining the product of said battery current reading and said temperature factor.

8. A monitoring unit as defined in claim 1, said processor means being operable during inactive conditions of no flow of charge current to or discharge current from said battery for periodically performing a self-discharge correction, each self-discharge operation serving to effect a reduction in said stored accumulated charge which is a function of elapsed time while in said inactive condition and since a last preceding self-discharge operation.

9. A monitoring unit as defined in claim 8, said processor means being operable during said inactive conditions to to perform a read operation including producing a battery temperature reading, said self-discharge correction serving to effect said reduction in said stored accumulated charge as a function of said temperature reading.

10. A monitoring unit as defined in claim 9, wherein the time between said periodically performed self-discharge correction is substantially constant, said reduction in said stored accumulated charge being reduced in accordance with a temperature factor which is a function of said battery temperature reading.

11. A monitoring unit as defined in claim 10, means storing a table of temperature factors in memory for access according to said temperature reading and to determine said reduction in said stored accumulated charge.

12. A monitoring unit for monitoring the condition of charge of a battery, comprising:

processor means operable during flow of charge current to said battery and discharge current from said battery for performing periodic read and processing operations, each read operation including producing a battery current reading corresponding to net current flowing to said battery, and each processing operation including producing an output reading from said battery current, and adding said output reading to a stored accumulated charge value indicating the condition of charge of said battery, said processor means being operable during inactive conditions of no flow of charge current to or discharge current from said battery for periodically performing a self-discharge correction, each self-discharge correction serving to effect a reduction in said stored accumulated charge which is a function of elapsed time while in said inactive condition and since a last preceding self-discharge correction.

13. A monitoring unit as defined in claim 12, said processor means being operable during said inactive conditions to to perform a read operation including producing a battery temperature reading, said self-discharge correction serving to effect said reduction in said stored accumulated charge as a function of said temperature reading.

14. A monitoring unit as defined in claim 13, wherein the time between said periodically performed self-discharge correction is substantially constant, said reduction in said stored accumulated charge being reduced in accordance with a temperature factor which is a function of said battery temperature reading.

15. A monitoring unit as defined in claim 14, means storing a table of temperature factors in memory for access according to said temperature reading and to determine said reduction in said stored accumulated charge.

16. A monitoring unit for monitoring the condition of charge of a battery, comprising:

battery temperature sensing means, and processor means coupled to said temperature sensing means and operable during flow of charge current to said battery for performing periodic temperature read and temperature-responsive processing operations, each temperature read operation including producing a temperature reading proportional to the current temperature of said battery, each processing operation including processing of said temperature reading to obtain data for use in subsequent processing operations, storing of such data, comparing said temperature reading and data stored during prior processing operations to develop a dT/dt value indicating a rate of change of temperature with time and to determine whether said dT/dt value is changing, and generating a full charge signal after said dT/dt value is increasing and when said dT/dt value exceeds a certain threshold value.

17. A monitoring unit as defined in claim 16, said processing operations further including reducing of said threshold value as a function of a decrease in said dT/dt value.

18. A monitoring unit as defined in claim 17, said reducing of said dT/dt value being limited to prevent reduction of said dT/dt value below a certain minimum value.

19. A monitoring unit as defined in claim 17, said reducing of said threshold value being commenced only after elapse of a certain time interval following a commencement of an operation to charge said battery from a discharged condition.

20. A monitoring unit as defined in claim 16, said processing operations further include reducing of said threshold value as a function of a decrease in said dT/dt value after charging of said battery to a certain condition while preventing reduction of said dT/dt value below a certain minimum value.

21. A monitoring unit for monitoring the charge of a battery which may supply power to circuitry of a host and may be charged from a charger associated with said host, said unit comprising:

sensing means for sensing the voltage of said battery and current flow to and from said battery, measuring circuitry coupled to said sensing means, processor means connected to said measuring circuitry for performing read and processing operations, each read operation including development of a battery voltage reading and battery current reading, transistor means for supplying an operating voltage to said measuring circuitry from said battery, said processor means being supplied with an operating voltage independent of that which is being supplied to said measuring circuitry, said processor means having a low power sleep condition and watch dog timer means for effecting a wake-up from said sleep condition upon elapse of a certain time interval after entering said sleep condition, and said processor means being operative upon a wake-up from said sleep condition to operate to sense a host-on condition in which said host should be in a condition in which said host circuitry or said charger may draw current from or supply current to said battery and being operative in response to sensing of said host-on condition for controlling said transistor means to supply said operating voltage to said measuring circuitry only during said on condition.

22. A monitoring unit as defined in claim 21, said processor means upon said wake-up from said sleep condition being operative to change the count registered by a counter and to sense a time-out at which a certain count has been registered by said counter, and said processor means being operative to enter said sleep condition upon sensing neither said time-out or said host-on condition.

23. A monitoring unit as defined in claim 22, said processor means being operable in response to said time-out of said counter for performing a self-discharge operation, each self-discharge operation serving to effect a reduction in a stored accumulated charge value which is a function of elapsed time while in said inactive condition and since a last preceding self-discharge operation.

24. A monitoring unit as defined in claim 23, said processor means being operable during said inactive conditions to to perform a read operation including producing a battery temperature reading, said self-discharge operations serving to effect said reduction in said stored accumulated charge as a function of said temperature reading.

25. A monitoring unit as defined in claim 24, wherein the time between said periodically performed self-discharge operations is substantially constant, said reduction in said stored accumulated charge being reduced in accordance with a temperature factor which is a function of said battery temperature reading.

26. A monitoring unit as defined in claim 25, means storing a table of temperature factors in memory for access according to said temperature reading and to determine said reduction in said stored accumulated charge.

27. A monitoring unit for monitoring the charge of a battery which may supply circuitry of a host and may be charged from a charger associated with said host, said unit comprising:

memory means, processor means operative for gathering and storing in said memory means information concerning the voltage of, current flow to and temperature of said battery and its condition of charge being operative for sending data to said host under control of said host.

28. A monitoring unit as defined in claim 27 said memory means including control data determining conditions of operation of said processor means, and said processor means being operative for sending said control data to said host under host control.

29. A monitoring unit as defined in claim 28, said memory means including control data determining conditions of operation of said processor means, and said processor means being operative for receiving instructions from said host and data for revision of said control data.

30. A monitoring unit comprising:

input means for supplying an input voltage to be measured, measuring means including ramp voltage generator means for generating a ramp voltage, comparator means coupled to said input means and said ramp voltage generator means, and processor means operative for controlling periodic operation of said ramp voltage generator means and coupled to said comparator means for registering digital input voltage data corresponding to a comparison of said ramp voltage with a voltage proportional to said input voltage and digital reference data corresponding to a comparison of said ramp voltage with a subtantially fixed voltage, said processor means being operative for processing said digital input voltage and reference data to develop output digital data proportional to the magnitude of said input voltage and substantially independent of changes in slope of said ramp voltage.

31. A monitoring unit as defined in claim 30, digital data storage means for storing digital calibration data developed at a calibration time and accessible by said processor means, and said processor means being operative for processing of said digital input voltage, reference and calibration data and for output of digital data which is directly proportional to said registered digital input voltage data, directly proportional to said digital calibration data and inversely proportional to said registered digital reference data, whereby to obtain in each periodic operation of said measuring means a dynamic correction for drifts in operation of said measuring means arising since said calibration time.

32. A monitoring unit as defined in claim 30, said ramp voltage generator means being operated peridically for generating a ramp voltage beginning at a starting time and changing in proportion to elapsed time since said starting time, said comparator means including first voltage comparator means for comparing said ramp voltage generated by said ramp voltage generator means and a voltage proportional to said input voltage to develop a first comparator output signal, second voltage comparator means for comparing said ramp voltage and a voltage proportional to said operating voltage to develop a second comparator output voltage, and said processor means being operative for initiating periodic operations of said ramp voltage generator means and being responsive to said first and second comparator output signals to develop said digital input voltage and reference data though counts of periodic signals from said initiating of said generating of said ramp voltage to receptions of said first and second comparator output signals.

33. A monitoring unit arranged for developing digital output data as a function of the value and polarity of an input voltage applied between an input terminal and a ground terminal, said unit comprising:

power supply means for supplying an operating voltage between said ground terminal and a supply voltage terminal, a measurement voltage divider including a first resistance means having one end connected to said supply voltage terminal and an opposite end connected to a measurement node and second resistance means having one end connected to said measurement node and an opposite end connected to said input terminal, and measuring means including analog to digital converter means operative for measuring a voltage at said measurement node and including means for producing a digital output reading corresponding to the value and polarity of said voltage at said input terminal.

34. A monitoring unit as defined in claim 33 for monitoring of current and including a current sense resistor between said input and ground terminals to produce said input voltage.

35. A monitoring unit as defined in claim 33, said measuring means being operable periodically including zero input means placed in an active condition and then in an inactive condition in each periodic operation of said measuring means, said zero input means being operable in an active condition to simulate a zero input voltage condition, said measuring means being operative for producing a reading of a first value of a measurement node voltage with said zero input means in said active condition and a reading of a second value of said measurement node voltage with said zero input means in said inactive condition, and said digital output reading being a function of a difference between said first and second values of said measurement node voltage.

36. A monitoring unit as defined in claim 35 for monitoring of current and including a current sense resistor between said input and ground terminals to produce said input voltage.

37. A monitoring unit as defined in claim 36, said second resistance means being divided to provide a zeroing node and a portion between said zeroing node and said opposite end having a resistance that is small fraction of the total resistance of said second resistance means but which is substantially higher than the resistance of said current sense resistor, said zero input means being connected to said zeroing node and being operative in said active condition thereof to develop a voltage at said zeroing node which is substantially independent of measured current.

38. A monitoring unit as defined in claim 35, means providing a bridge unit which includes said measurement voltage divider and which includes a reference voltage divider, said reference voltage divider including third resistance means having one end connected to said supply voltage terminal and an opposite end connected to a reference node and fourth resistance means having one end connected to said reference node and an opposite end connected to said ground terminal, said measuring means being operative for producing a first value of a reference node voltage with said zero input means in said active condition and a second value of a reference node voltage with said zero input means in an inactive condition, said first value of said reference node voltage differing from said first value of said measurement node voltage as a function of any unbalance in said bridge circuit that is independent of said input voltage and said second value of said reference node voltage differing from said second value of said measurement node voltage as a function of any unbalance in said bridge circuit affected by said input voltage, and said digital output reading being both a function of a difference between said first and second reference values and a function of a difference between said first and second measurement values.

39. A monitoring unit as defined in claim 38 for monitoring of current and including a current sense resistor between said input and ground terminals to produce said input voltage in response to current flow through said current sense resistor.

40. A monitoring unit as defined in claim 39, said second resistance means being divided to provide a first control node and a portion between said first control node and said opposite end of said second resistance means having a resistance that is small fraction of the total resitance of said second resistance means but which substantially higher than the resistance of said current sense resistor, said fourth resistance means being divided to provide a second control node and a portion between said second control node thereof and said opposite end thereof, said zero input means being connected to said first and second control nodes and being operative in said active condition thereof to place both of said first and seond control nodes at substantially the same potential relative to ground potential.

41. A monitoring unit as defined in claim 40, said zero input means comprising transistor means connected between said first and second control nodes and rendered conductive in said active condition of said zero input means.

42. A monitoring unit as defined in claim 41, said zero input means comprising first and second control means connected to said first and second control nodes and operative in said active condition of said zero input means to provide separate low resistance paths from said first and second control nodes to said ground terminal.

43. A monitoring unit as defined in claim 41, measuring means comprising processor means having a pair of pins connected to said first and second control nodes to provide said first and second control means, each of said pins being selectively operable in either a tri-state mode or in a conductive mode to provide a low resistance path to ground, and a pair of pins pins connected to said control nodes and controllable to provide said pair of means connected to said control nodes.

44. A measuring unit comprising:

ramp voltage generator means for generating a ramp voltage, a plurality of comparator means each operative for comparing said ramp voltage and an input voltage and producing an output signal which changes in state in response to a certain difference between said ramp voltage and said input voltage, and processor means coupled to said ramp voltage means and including data storage registers and a port for input of said output signals from said plurality of comparator means, said processor means being operative to perform a read operation including initiating generation of said ramp voltage and then performing periodic test operations, each test operation including effecting a one count change in current count data, registering of port data indicating the status of said output signals from said comparator means, detecting any change in data in said port data from port data registered in a last preceding test operation and responding to any such change in data by registering change data as to said change in said plural bit digital data, said change data together with said current count data providing data as to the relative magnitude of said ramp voltage and of any input voltage which produced a change in state of any one of said plurality of comparators since said last preceding test operation.

45. A measuring unit as defined in claim 44, said measurement data determining operation including storage in a mask register of plural bit data each bit corresponding to one of said comparator means, a logical operation to compare said data in said mask register with current port data and to develop said change data, and storage in said mask register of data corresponding to current port data for use in a next subsequent test operation to detect any change in port data.

46. A measuring unit as defined in claim 45, said processor means being operative to discontinue generation of said ramp voltage when said current count reaches a certain value in excess of an expected maximum value of any of said second voltage applied to said second inputs of said comparator means.

47. A measuring unit as defined in claim 46, each of said test operations including storage in temporary storage registers of said change data and corresponding current count data, and said processor means being operative after discontinuing generation of said ramp voltage to process and sort data stored in said temporary storage registers to produce a reading for each of said comparator means corresponding to a count registered in response to a change in state thereof.