Apparatus for monitoring the state of charge of a battery

• US 4,968,941 A
• Filed: 07/13/1988
• Issued: 11/06/1990
• Est. Priority Date: 07/13/1988
• Status: Expired due to Term

• Current Assignee: Electronic Development Inc.
• Original Assignee: Electronic Development Inc.
• Inventors: Rogers, Wesley A.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Mueller, Robert W.
• Application Number:
  US07/218,539
• Time in Patent Office: 846 Days
• Field of Search: 324/426, 324/427, 324/428, 324/435, 340/636, 320/48
• US Class Current: 324/428
• CPC Class Codes: G01R 1/203 Resistors used for electric measuring, e.g. decade resistors standards, resistors for comparators, series resistors, shunts resistors in general H01C; microwave or radiowave terminations H01P1/26; coupling devices H01R
• CPC Class Codes: G01R 31/382 Arrangements for monitoring battery or accumulator variables, e.g. SoC
• CPC Class Codes: H02J 7/1423 with multiple batteries

Abstract

An apparatus for monitoring the state of charge of a battery having a shunt resistor connected in series with a battery and an integrating circuit connected across the terminals of the shunt resistor is provided. The integrating circuit includes a Memoriode having a large capacitance and the capability to store charge for long periods of time, so that the integration can be performed along the same curve even if power to the integrating circuit is interrupted.

Claims

1. An apparatus for monitoring the state of charge of a battery comprising:

a shunt resistor to be placed in series with said battery and having a voltage drop related to the current to or from said battery;

and an electrical long term analog integrator connected across said shunt resistor for integrating said voltage drop;

said integrator comprising an operational amplifier, an input resistor connected in series to a first input of said operational amplifier, and a MEMORIODE connected in series between said first input and the output of said operational amplifier;

said MEMORIODE being operatively connected for non-volatile storage of said monitored state of charge without requiring connection of said apparatus, said integrator, or said MEMORIODE to said battery or other source of power.

2. The apparatus of claim 1 further comprising:

a charging circuit for selectively charging said memoriode to a voltage level corresponding to the level of charge of said battery,

a voltage limiter circuit for sensing a voltage output of said memoriode and limiting said voltage,

a circuit for sensing high current discharges from said battery and for changing the discharge rate of said memoriode,

a circuit for sensing discharge currents from said battery and for providing power to said integrating circuit during said discharge currents,

a circuit for sensing charging currents from said battery and for providing power to said integrating circuit during said charging currents.

3. The apparatus of claim 2, further comprising a display means for showing the state of charge of said battery.

4. The apparatus of claim 1, wherein said memoriode functions to store a charge related to said battery'"'"'s state of charge for long periods of time.

5. The apparatus of claim 4, wherein said memoriode retains said stored charge without requiring connection of said apparatus, said integrator, or said memoriode to said battery or to another power supply.

6. An apparatus for monitoring the state of charge of a battery comprising:

a current sensor operatively connected to said battery for producing an output signal related to the magnitude and sign of the current flowing to or from said battery;

an electrical long term analog integrator connected to said current sensor for integrating said output signal and for producing a signal related to said battery'"'"'s state of charge;

said integrator including a long term charge storage device for storing a charge related to said battery'"'"'s state of charge;

said long term charge storage device being operatively connected to said apparatus such that said charge is non-volatile without requiring connection of said long term charge storage device, said integrator, or said apparatus to either said battery or other power supply.

7. The apparatus of claim 6, further comprising an indicator connected to said integrator for indicating the state of said signal related to said battery'"'"'s state of charge.

8. The apparatus of claim 7, wherein said indicator produces a visual indication of said battery'"'"'s state of charge.

9. The apparatus of claim 7, wherein said indicator produces an audible indication of said battery'"'"'state of charge.

10. The apparatus of claim 6, wherein said integrator further comprises:

a current source having an input connected to said current sensor and an output connected to said long term charge storage device;

said input controlling the magnitude and sign of said output such that said current source operates to charge and discharge said long term charge storage device in response to said current flowing to or from said battery.

11. The apparatus of claim 10, wherein said current source further comprises an operational amplifier and said long term charge storage device is connected in a feedback path of said operational amplifier.

12. The apparatus of claim 11, wherein said operational amplifier has a high input impedance to thereby inhibit decay of said charge stored in said long term charge storage device.

13. The apparatus of claim 12, wherein said long term charge storage device comprises a memoriode.

14. The apparatus of claim 6, wherein said long term charge storage device comprises a MEMORIODE.

15. The apparatus of claim 14, wherein said integrator further comprises an operational amplifier and a resistor connected in series to a first input of said operational amplifier, said memoriode being connected in series between said first input and the output of said operational amplifier.

16. The apparatus of claim 14, wherein the output of said integrator is connected to a display for displaying the state of charge of said battery.

17. The apparatus of claim 16, wherein said display is an analog meter.

18. The apparatus of claim 16, wherein said display is a red, green and yellow bar graph display.

19. The apparatus of claim 14, further comprising an initializing circuit, for selectively charging said memoriode to a voltage level corresponding to the level of charge of said battery.

20. The apparatus of claim 14, further comprising a voltage limiter circuit for sensing a voltage output of said memoriode and limiting said voltage to a maximum level.

21. The apparatus of claim 14, further comprising a circuit for sensing high current discharges from said battery and for changing discharge rate of said memoriode during said high current discharge.

22. The apparatus of claim 21, further comprising a relay and a second resistor, said relay being actuated by said circuit for sensing high current discharges to switch said second resistor to provide a discharge path for said memoriode.

23. The apparatus of claim 14, further comprising a circuit for sensing discharge currents from said battery and for providing power to said means for integrating during said discharge currents.

24. The apparatus of claim 14, further comprising circuit for sensing charging currents from said battery and for providing power to said means for integrating during said charging currents.

25. The apparatus of claim 6, wherein only discharge currents flowing from said battery are monitored.

26. The apparatus of claim 6, wherein only charge currents flowing from said battery are monitored.

27. The apparatus of claim 6, wherein both charge and discharge currents flowing to or from said battery are monitored.

28. The apparatus of claim 6, further comprising:

an automatic on-off circuit connected to said current sensor for activating portions of said apparatus when said battery is being charged and deactivating said portions when said battery is not being charged;

said automatic on-off circuit having preset threshold levels for activating and deactivating said portions in response to charge currents flowing to said battery.

29. The apparatus of claim 6, further comprising:

an automatic on-off circuit connected to said current sensor for activating portions said apparatus when said battery is being discharged and deactivating said portions when said battery is not being discharged;

said automatic on-off circuit having present threshold levels for activating and deactivating said portions in response to discharge currents flowing from said battery.

30. The apparatus of claim 6, further comprising:

an automatic on-off circuit connected to said current sensor for activating portions of said apparatus when said battery is in use and deactivating said portions when said battery is not in use;

said automatic on-off circuit having preset threshold levels for activating and deactivating said portions in response to said current flowing to or from said battery.

31. The apparatus of claim 6, further comprising:

a voltage limiter circuit connected to said integrator for detecting the voltage across said long term charge storage device and operative to limit said voltage to a preset maximum value.

32. The apparatus of claim 6, further comprising:

a high discharge current level detector for rapidly altering said stored charge in said long term charge storage device in response to levels of said current flowing from said battery which exceed a predetermined threshold.

33. The apparatus of claim 6, further comprising an initialization circuit for presetting said stored charge.

34. The apparatus of claim 33, wherein said initialization circuit is connected to said long term charge storage device for selectively presetting said stored charge to a value related to said battery'"'"'s state of charge at the time of connection of said battery to said apparatus.

35. The apparatus of claim 6, further comprising a discharge circuit connected to said long term charge storage device providing a discharge path for discharging said long term charge storage device at a rate related to said battery'"'"'s self discharge characteristics to more accurately track said battery'"'"'s state of charge.

36. An apparatus for monitoring the state of charge of a battery comprising:

a current sensor operatively connected to said battery for producing an output signal related to the magnitude and sign of the current flowing to or from said battery;

an electrical long term analog integrator connected to said current sensor for integrating said output signal and for producing a signal related to said battery'"'"'s state of charge;

said integrator comprising a long term charge storage device for storing a charge related to said battery'"'"'s state of charge and a current source having an input connected to said current sensor and an output connected to said long term charge storage device;

said long term charge storage device retaining said charge for long periods of time without requiring connection of said long term charge storage device, said integrator, or said apparatus to either said battery or other power supply;

said input controlling the magnitude and sign of said output such that said current source operates to charge and discharge said long term charge storage device only in response to said current flowing to or from said battery, said charge not being altered by loss of power to said integrator;

an automatic on-off circuit connected to said current sensor for activating portions of said apparatus when said battery is in use and deactivating said portions when said battery is not in use;

said automatic on-off circuit having preset threshold levels for activating and deactivating said portions in response to said current flowing to or from said battery.

37. The apparatus of claim 36, further comprising:

a voltage limiter circuit connected to said integrator for detecting the voltage across said long term charge storage device and operative to limit said voltage to a preset maximum value.

38. The apparatus of claim 36, further comprising a discharge circuit connected to said long term charge storage device providing a discharge path for discharging said long term charge storage device at a rate related to said battery'"'"'s self discharge characteristics to more accurately track said battery'"'"'s state of charge.

39. The apparatus of claim 36, wherein said long term charge storage device comprises a memoriode.

40. An apparatus for monitoring the state of charge of a battery comprising:

a current sensor operatively connected to said battery for producing an output signal related to the magnitude and sign of the current flowing to or from said battery;

an electrical integrator connected to said current sensor for integrating said output signal and for producing a signal related to said battery'"'"'s state of charge;

a long term charge storage device forming a part of said integrator for storing a charge related to said battery'"'"'s state of charge;

said long term storage device retaining said charge for long periods of time without requiring connection of said long term charge storage device, said integrator, or said apparatus to either said battery or other power supply;

said integrator comprising a current source having an input connected to said current sensor and an output connected to said long term charge storage device;

said input controlling the magnitude and sign of said output such that said current source operates to charge and discharge said long term charge storage device in response to said current flowing to or from said battery;

an automatic on-off circuit connected to said current sensor for activating portions of said apparatus when said battery is in use and deactivating said portions when said battery is not in use;

said automatic on-off circuit having preset threshold levels for activating and deactivating said portions in response to said current flowing to or from said battery; and

an initialization circuit connected to said long term charge storage device for selectively presetting said stored charge to a value related to said battery'"'"'s state of charge.

41. The apparatus of claim 40, further comprising a discharge circuit connected to said long term charge storage device providing a discharge path for discharging said long term charge storage device at a rate related to said battery'"'"'s self discharge characteristics to more accurately track said battery'"'"'s state of charge.

42. The apparatus of claim 40, wherein said long term charge storage device comprises a memoriode.