Electronic battery testing device

• US 3,873,911 A
• Filed: 02/22/1973
• Issued: 03/25/1975
• Est. Priority Date: 09/14/1971
• Status: Expired due to Term

• Current Assignee: Keith S Champlin
• Original Assignee: Keith S Champlin
• Inventors: Champlin, Keith S.
• Primary Examiner(s): Smith, Alfred E.
• Assistant Examiner(s): Karlsen, Ernest F.
• Application Number:
  US05/334,667
• Time in Patent Office: 761 Days
• Field of Search: 324/29.5,62R 320/48 340/249
• US Class Current: 324/430
• CPC Class Codes: G01R 17/10 AC or DC measuring bridges
• CPC Class Codes: G01R 27/02 Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant by measuring phase angle only G01R25/00
• CPC Class Codes: G01R 31/379 for lead-acid batteries
• CPC Class Codes: G01R 31/385 Arrangements for measuring battery or accumulator variables for monitoring G01R31/382
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables

Abstract

A self-contained electronic device for testing storage batteries is disclosed. The testing device is electrically connected to the battery undergoing test by means of special spring clips. Electronic circuitry in the testing device effectively detects and measures the battery'"'"''"'"'s inverse dynamic resistance through the use of an oscillator operating at approximately 100 Hz. This detection and measurement is then displayed in units of dynamic power. Dynamic power is directly proportional to the inverse dynamic resistance and is found to an an accurate and sensitive indicator of the battery'"'"''"'"'s condition and state-of-charge. Two embodiments of the invention are described, the first being a modified bridge circuit to determine inverse dynamic resistance and the second being a direct reading instrument based on the use of dynamic resistance to control the negative feedback of a highgain amplifier.

Claims

1. A measuring device for assessing the condition of a direct current source of electricity comprIsing:

a. means providing a time-varying signal;

b. electrical connecting means constructed and arranged to be connected to each output terminal of said direct current source of electricity, each of said connecting means containing both a first conductor and a second conductor separately contacting each of said terminals, said first and second conductors reducing the effects of contact and lead-wire resistance;

c. electrical means for applying a time-varying current derived from said time-varying signal through said direct current source of electricity by means of a pair of said first conductors, for sensing the resultant time-varying potential across said direct current source of electricity by means of a pair of said first conductors, for sensing the resultant timevarying potential across said direct current source of electricity by means of a pair of said second conductors, and for utilizing said time-varying potential to determine the reciprocal of the dynamic resistance of said direct current source of electricity at frequencies such that the reactive component of the ac impedance of said direct current source is substantially small in comparison with the resistive component of same;

d. and indicating means connected to said electrical means including pointer means and scale means, the position of said pointer means relative to said scale means during measurement being substantially proportional to the reciprocal of the dynamic resistance of said direct current source of electricity, said scale means subsequently relating said relative position to the condition of said direct current source of electricity.

2. Apparatus as set forth in claim 1 wherein said electrical means and said indicating means include a variable electrical element and an output detector, said position of said pointer means relative to said scale means being specified by the value of said variable electrical element required to obtain a predetermined condition of said output detector.

3. Apparatus as set forth in claim 1 wherein said electrical means and said indicating means include an electrical meter, said position of said pointer means relative to said scale means being specified by the signal applied to said electrical meter.

4. Apparatus as set forth in claim 1 wherein said electrical means includes a bridge circuit excited by said time-varying signal, said bridge circuit containing said direct current source in its unknown arm and variable resistance means in the arm diagonally opposite, said bridge circuit being modified by extending the two conductors which define each end of said unknown arm so that they make separate contact with the output terminals of said direct current source by means of said first and second conductors of said electrical connecting means, said electrical means further including means for amplifying the output voltage of said bridge and means for detecting the condition of minimum output voltage, said position of said pointer means relative to said scale means being specified by the value of said variable resistance means required to obtain minimum time-varying output voltage.

5. Apparatus as set forth in claim 4 wherein the bandwidth of said amplifying means, defined by halfpower frequencies, is less than 25 percent of the frequency of maximum amplification.

6. Apparatus as set forth in claim 4 wherein the output voltage of said amplifying means saturates when said bridge is unbalanced.

7. Apparatus as set forth in claim 4 wherein said detecting means includes a dc milliammeter biased to nearly full scale deflection with direct current, and a rectifier rectifying the output of said amplifying means so that it subtracts from the total positive milliammeter current.

8. Apparatus as set forth in claim 4 wherein the output voltage of said bridge circuit is applied to, and attenuated by, a potentiometer ganged to said variable resistance.

9. A measuring device for assessing the condition of a direct current sOurce of electricity comprising:

a. means providing a time-varying signal;

b. electrical connecting means constructed and arranged to be connected to each output terminal of said direct current source of electricity;

c. high gain amplifier means;

d. means capacitively coupling across the input of said high gain amplifier means, the combination of said means providing a time-varying signal and said direct current source of electricity through said electrical connecting means;

e. feedback means coupling a signal representative of the output of said high gain amplifier means across said direct current source of electricity by means of said electrical connecting means; and

f. voltmeter means connected to said high gain amplifier means for displaying readings representative of the amplitude of the time-varying output signal thereof, said voltmeter means relating said readings to the condition of said direct current source of electricity.

10. Apparatus as set forth in claim 9 wherein said time-varying signal contains frequency components to cause the reactance of said direct current source of electricity to be substantially small in comparison with its dynamic resistance.

11. Apparatus as set forth in claim 9 wherein said means providing same time-varying signal includes an oscillator contained in said measuring device which generates said time-varying signal.

12. Apparatus as set forth in claim 11 wherein said oscillator generates a square wave having amplitude proportional to the supply voltage of said oscillator.

13. Apparatus as set forth in claim 9 including variable attenuator means connected between the output of said means providing a time-varying signal and said high gain amplifier means to permit initial calbiration of said measuring device.

14. Apparatus as set forth in claim 9 wherein the last stage of said high gain amplifier means includes a power transistor having a load resistor providing a feedback path to said direct current source of electricity.

15. Apparatus as set forth in claim 1 wherein said means providing a time-varying signal and said electrical means are electrically energized from said direct current source of electricity.

16. Apparatus as set forth in claim 9 wherein said means for providing a time-varying signal and said high gain amplifier means are electrically energized from said direct current source of electricity.

17. Apparatus as set forth in claim 1 wherein said scale means is calibrated in units that are directly proportional to the power delivering capability of said direct current source.

18. Apparatus as set forth in claim 1 wherein said means providing the time-varying signal includes an oscillator contained in said measuring device which generates said time-varying signal.

19. Apparatus as set forth in claim 1 wherein said electrical connecting means includes spring actuated clips providing temporary contact to the output terminals of said direct current source.

20. Apparatus as set forth in claim 1 wherein said electrical connecting means includes spring actuated clips, each of said clips containing both a first conductor and a second conductor providing separate temporary contact to said output terminals.

21. Apparatus as set forth in claim 9 wherein each of said electrical connecting means contains both a first conductor and a second conductor separately contacting said output terminals, a pair of said first conductors providing a conducting path for coupling a current representative of the output signal of said high gain amplifier means through said direct current source of electricity and a pair of said second conductors providing a separate conducting path for coupling the resultant time-varying voltage developed across said direct current source back to the combination of said means providing a time-varying signal and the input of said high gain amplifier means.

22. Apparatus as set forth in claim 9 wherein said electrical connecting means includes spring actuated clips providing temporary contact to said output terminals.

23. Apparatus as set forth in claim 9 wherein said voltmeter means is calibrated in units that are directly proportional to the power delivering capability fo said direct current source of electricity.

24. Apparatus as set forth in claim 9 wherein said voltmeter means is calibrated in watts.

25. Apparatus as set forth in claim 9 wherein said high gain amplifier means has a differential input, each terminal of which is capacitively coupled to the series combination of said means providing a time-varying signal and said direct current source of electricity.