Electronic tester for assessing battery/cell capacity

• US 5,140,269 A
• Filed: 09/10/1990
• Issued: 08/18/1992
• Est. Priority Date: 09/10/1990
• Status: Expired due to Term

• Current Assignee: Keith S Champlin
• Original Assignee: Keith S Champlin
• Inventors: Champlin, Keith S.
• Primary Examiner(s): Wieder, Kenneth A.
• Assistant Examiner(s): BROWN, GLENN WARNER
• Application Number:
  US07/579,817
• Time in Patent Office: 708 Days
• Field of Search: 324/426, 324/430, 324/433, 324/435, 324/436, 320/48, 340/636
• US Class Current: 324/433
• CPC Class Codes: G01R 19/16542 for batteries charge condition monitoring in G01R31/36
• CPC Class Codes: G01R 31/379 for lead-acid batteries
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables

Abstract

A self-contained electronic device instantaneously assesses the stored energy capacity of single, two-volt, lead-acid cells; or of batteries comprised of such cells. The testing device is electrically connected to the terminals of a cell or battery and measures its dynamic conductance with a small, time-varying signal. An internal conductance standard permits initial calibration of the device to assure accuracy of the cell/battery measurements. Means are provided for entering a "reference conductance", defined to be the dynamic conductance of an identically rated and constructed cell or battery having 100% energy capacity. The device displays either the test cell/battery'"'"'s measured conductance in Siemens (mhos), or its "percent capacity" determined by appropriately scaling its measured conductance in accordance with the "reference conductance". When determining "percent capacity", an LED lights if the result is less than a preset threshold value. For single-cell operation, special design features permit energizing the higher current elements of the measuring circuit directly from two-volt cell undergoing test while energizing the lower current, but higher voltage, elements from a separate, low-power, dc source such as a small 9-volt transistor battery or an integral dc/dc converter powered by the cell undergoing test. This novel circuit arrangement results in the realization of a portable, self-contained, electronic instrument that provides an accurate, instantaneous, assessment of the "percent capacity" of a two-voltage cell, or a battery comprised of such cells, without requiring any connection to external power.

Claims

1. A process for assessing the percent capacity of a cell or battery comprising the steps of:

measuring the dynamic conductance of said cell or battery with a time-varying signal;

establishing a reference dynamic conductance defined as the dynamic conductance of an identically constructed cell or battery having substantially 100 percent capacity;

taking a ratio of said measured dynamic conductance to said reference dynamic conductance; and

displaying said ratio expressed as a percentage.

2. A process for determining whether the percent capacity of a cell or battery is less than a predetermined value comprising the steps of:

measuring the dynamic conductance of said cell or battery with a time-varying signal;

establishing a reference dynamic conductance defined as the dynamic conductance of an identically constructed cell or battery having substantially 100 percent capacity;

taking a ratio of said measured dynamic conductance to said reference dynamic conductance; and

indicating whether said ratio is less than a predetermined value.

3. An electronic device for assessing the level of energy stored in a cell or battery relative to a reference level, said cell or battery having a dynamic conductance, comprising:

means for measuring said dynamic conductance operably connected to said cell or battery and providing a measured dynamic conductance value;

means for entering a reference dynamic conductance value into said electronic device;

means for comparing said measured dynamic conductance value with said reference dynamic conductance value and determining the ratio thereof; and

means responsive to said ratio for providing an assessment of said level of energy stored in said cell or battery relative to said reference level.

4. An electronic device in accordance with claim 3 wherein said means responsive to said ratio comprises means for indicating if said ratio is less than a predetermined value.

5. An electronic device in accordance with claim 3 wherein said means responsive to said ratio comprises means for displaying numbers proportional to said ratio.

6. An electronic device in accordance with claim 3 including means responsive to said measured dynamic conductance value for displaying said measured dynamic conductance value.

7. An electronic device in accordance with claim 6, including:

conductance standard means for providing a conductance standard reference; and

calibration adjustment means for adjusting said measured dynamic conductance value, wherein said means for measuring is adapted to measure said conductance standard reference, and said calibration adjustment means is adjusted to cause said means responsive to said measured dynamic conductance value for displaying said measured dynamic conductance value to display a predetermined value.

8. An electronic device in accordance with claim 3 wherein said means for measuring includes oscillator means for oscillating, voltage amplifying means for amplifying voltage, power amplifying means for amplifying power, and auxiliary dc power means for providing auxiliary dc power, wherein said power amplifying means receives dc operating power directly from said cell or battery, and said oscillator means and voltage amplifying means each receive dc operating power from said auxiliary dc power means.

9. An electronic device in accordance with claim 8 wherein said auxiliary dc power means comprises a dc to dc converter energized by said cell or battery.

10. An electronic device in accordance with claim 8 wherein said auxiliary dc power means comprises a separate battery power source.

11. An electronic device for displaying the energy capacity of a test cell or battery relative to that of a reference, comprising:

an oscillator providing a time-varying input signal;

a feedback amplifier, operably connected to said oscillator and to said test cell or battery, said feedback amplifier providing an output signal directly proportional to said time-varying input signal and to the admittance of said test cell or battery;

an adjustable attenuator, operably connected to said feedback amplifier, for variably scaling the level of said output signal in concordance with the conductance of said reference;

a detector for converting said output signal into a variably scaled dc voltage; and

a display device, responsive to said variably scaled dc voltage, for displaying said energy capacity of said test cell or battery relative to that of said reference.

12. An electronic device in accordance with claim 11 wherein said display device includes a signaling device for providing a qualitative indication of the size of said variably scaled dc voltage relative to a predetermined value.

13. An electronic device in accordance with claim 12 wherein said signaling device comprises a light emitting diode.

14. An electronic device in accordance with claim 11 wherein said display device comprises a numerical display device for displaying numbers proportional to said variably scaled dc voltage.

15. An electronic device in accordance with claim 11, including a numerical conductance display, further comprising:

a fixed attenuator, operably connected to said feedback amplifier, for constantly scaling the level of said output signal;

a detector for converting said output signal into a constantly scaled dc voltage; and

a numerical conductance display, responsive to said constantly scaled dc voltage, for displaying numbers proportional to said constantly scaled dc voltage.

16. An electronic device in accordance with claim 15, including a calibration circuit, further comprising:

a conductance standard operably connected to said cell or battery;

a switch interconnecting said conductance standard, said test cell or battery, and said feedback amplifier means, said switch capable of adapting said feedback amplifier to provide an output signal that is independent of said admittance of said test cell or battery and directly proportional to the conductance of said conductance standard; and

a calibration variable attenuator, operably connected to said feedback amplifier, and adapted to setting the level of said output signal in concordance with the conductance of said conductance standard with said feedback amplifier adapted to provide an output signal that is independent of said admittance of said test cell or battery and directly proportional to the conductance of said conductance standard.

17. An electronic device in accordance with claim 11 including an auxiliary dc power source, wherein said feedback amplifier comprises a voltage amplifier and a power amplifier, said power amplifier receiving dc operating power directly from said cell or battery and said voltage amplifier and sad oscillator each receiving dc operating power from said auxiliary dc power source.

18. An electronic device in accordance with claim 17 wherein said auxiliary dc power source comprises a dc to dc converter energized by said cell or battery.

19. An electronic device in accordance with claim 17 wherein said auxiliary dc power source comprises a separate battery power source.

20. An electronic device for testing a cell or battery comprising:

an auxiliary dc power source;

a high-gain amplifier having an input and an output comprising a voltage amplifier and a power amplifier, said power amplifier adapted to receive dc operating power directly from said cell or battery, and said voltage amplifier adapted to receive dc operating power and dc input bias from said auxiliary dc power source, said dc input bias being passed through an isolating current source;

internal voltage-feedback means for providing voltage feedback to said high-gain amplifier, including a low-pass filter interconnecting the output and the input of said high-gain amplifier;

external current-feedback means for providing current feedback to said high-gain amplifier, including a feedback resistance conducting a current from the output of said high-gain amplifier through said cell or battery;

oscillator means for producing a periodic oscillator signal, said oscillator means adapted to receive dc operating power from said auxiliary dc power source;

voltage summing and coupling means for adding a voltage derived from said periodic oscillator signal to a voltage across said cell or battery, and capacitively coupling the sum voltage to said input of said high-gain amplifier;

detector means for producing a dc output signal in response to an ac voltage across said feedback resistance; and

indicating means, responsive to the level of said dc output signal, for indicating results of said test.

21. An electronic device in accordance with claim 20 wherein said auxiliary dc power source comprises a dc to dc converter energized by said cell or battery.

22. An electronic device in accordance with claim 20 wherein said auxiliary dc power source comprises a separate battery power source.

23. An electronic device in accordance with claim 20 wherein said indicating means provides a qualitative response to said level of said dc output signal.

24. An electronic device in accordance with claim 20 wherein said indicating means provides a quantitative response to said level of said dc output signal.

25. An electronic device employing a time-varying current to test a cell or battery comprising:

a pair of current-carrying contacts operably contacting said cell or battery;

a power amplifier operably arranged to receive dc operating power from said cell or battery by means of said current-carrying contacts and to pass said time-varying current through said cell or battery by means of said current-carrying contacts, said time-varying current producing a time-varying signal voltage across said cell or battery;

a pair of voltage-sensing contacts sensing said time-varying signal voltage across said cell or battery;

an auxiliary dc power source;

a voltage amplifier operably arranged to receive dc operating power from said auxiliary dc power source and to amplify an input signal derived from said time-varying signal voltage across said cell or battery as sensed by said voltage-sensing contacts;

a detector operably arranged to provide a dc signal voltage proportional to the time-varying output signal of said voltage amplifier; and

a display device, responsive to the level of said dc signal voltage, displaying results of said test.

26. An electronic device in accordance with claim 25 wherein said auxiliary dc power source comprises a dc to dc converter energized by said cell or battery through said current-carrying contacts.

27. An electronic device in accordance with claim 25 wherein said auxiliary dc power source comprises a separate battery power source.

28. An electronic device in accordance with claim 25 wherein said power amplifier comprises a bipolar power transistor.

29. An electronic device in accordance with claim 25 wherein said power samplifier comprises a power MOSFET.

30. An electronic device in accordance with claim 25 wherein said display device provides a qualitative indication of a magnitude of said level of said dc signal voltage relative to a reference level.

31. An electronic device in accordance with claim 25 wherein said display device displays numbers proportional to said level of said dc signal voltage.

32. An electronic circuit providing a dc output signal directly proportional to the conductance of a length of conductor connected in series with a cell or battery comprising:

an amplifier cascade comprising a high-gain voltage amplifier followed by a power amplifier;

a dc voltage-feedback network, including a low-pass filter network, said dc voltage-feedback network interconnecting the output terminals of said power amplifier with the input terminals of said high-gain voltage amplifier;

an ac feedback current loop, including a feedback resistor, said ac feedback current loop comprising the series interconnection of the output terminals of said power amplifier, said length of conductor, said cell or battery, and said feedback resistor;

an oscillator circuit producing a periodic oscillator signal;

a first pair of voltage-sensing contacts sensing a voltage developed across said length of conductor;

a voltage summing and coupling network adding a voltage derived from said periodic oscillator signal to said voltage sensed by said first pair of voltage-sensing contacts and capacitively coupling a sum voltage to the input terminals of said high-gain voltage amplifier; and

a detector circuit, responsive to an ac current flowing in said ac feedback current loop, and producing said dc output signal in proportion to the component of said ac current that is in phase with said periodic oscillator signal.

33. An electronic circuit in accordance with claim 32 wherein said power amplifier comprises a bipolar power transistor and said power amplifier output terminals comprise emitter and collector terminals.

34. An electronic circuit in accordance with claim 32 wherein said power amplifier comprises a power MOSFET and said power amplifier output terminals comprise source and drain terminals.

35. An electronic circuit in accordance with claim 32 including an auxiliary dc power source providing operating power to said oscillator circuit and to said high-gain voltage amplifier.

36. An electronic circuit in accordance with claim 35 wherein said auxiliary dc power source comprises a dc to dc converter energized by said cell or battery.

37. An electronic circuit in accordance with claim 35 wherein said auxiliary dc power source comprises a separate battery power source.

38. An electronic circuit in accordance with claim 32 including means for changing operational modes from a first operational mode providing a dc output signal directly proportional to the conductance of said length of conductor to a second operational mode providing a dc output signal directly proportional to the conductance of said cell or battery, said means for changing operational modes comprising:

a second pair of voltage-sensing contacts sensing a voltage developed across said cell or battery; and

a mode selector switch, interposed between said first and second pairs of voltage-sensing contacts and said voltage summing and coupling network, and arranged to select either said voltage sensed by said first pair of voltage-sensing contacts in said first operational mode, or said voltage sensed by said second pair of voltage-sensing contacts in said second operational mode, for presentation to said voltage summing and coupling network.

39. An electronic circuit in accordance with claim 38 wherein said electronic circuit includes a dc output signal level adjustment and said length of conductor comprises a conductance standard, said electronic circuit being calibrated by adjusting said dc output signal level adjustment to place said dc output signal level in concordance with the conductance value of said conductance standard with said selector switch selecting said first operational mode.

40. A process for assessing the condition of a deep-cycle cell or battery relative to that of a reference cell or battery comprising the steps of:

passing a time-varying current through deep-cycle cell or battery and sensing a time-varying voltage across said deep-cycle cell or battery;

determining a measured ratio of a component of said time-varying current to a component of said time-varying voltage;

comparing said measured ratio with a reference ratio appropriate to said reference cell or battery; and

displaying the result of said comparison.

41. A process as in claim 40 wherein said result of said comparison is displayed with numbers that are proportional to said measured ratio divided by said reference ratio.

42. A process as in claim 40 wherein said result of said comparison is displayed by indicating whether said measured ratio is greater or less than a particular fraction of said reference ratio.

43. An electronic device for assessing the condition of a deep-cycle cell or battery relative to that of a reference cell or battery comprising:

means operably connected to said deep-cycle cell or battery for passing a time-varying current through said deep-cycle cell or battery and for sensing a time-varying voltage across said deep-cycle cell or battery;

means for determining a measured ratio of a component of said time varying current to a component of said time-varying voltage;

means for comparing said measured ratio with a reference ratio appropriate to said reference cell or battery; and

means for displaying the result of said comparison.

44. An electronic device as in claim 43 wherein said means for displaying the result of said comparison displays numbers that are proportional to said measured ratio divided by said reference ratio.

45. An electronic device as in claim 43 wherein said means for displaying the result of said comparison indicates whether said measured ratio is greater or less than a particular fraction of said reference ratio.