SUPPRESSING HF CABLE OSCILLATIONS DURING DYNAMIC MEASUREMENTS OF CELLS & BATTERIES

• US 20140002094A1
• Filed: 03/12/2013
• Published: 01/02/2014
• Est. Priority Date: 06/28/2012
• Status: Active Grant

• Current Assignee: Keith S Champlin
• Original Assignee: Keith S Champlin
• Inventors: Champlin, Keith S.
• Granted Patent: US 9,851,411 B2
• Time in Patent Office: Days
• US Class Current: 324/426
• CPC Class Codes: G01R 1/06 Measuring leads; Measuring probes G01R19/145, G01R19/165 take precedence
• CPC Class Codes: G01R 27/14 Measuring resistance by measuring current or voltage obtained from a reference source G01R27/16, G01R27/20, G01R27/22 take precedence
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• 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

Kelvin (4-wire) connecting cables are routinely used when performing dynamic measurements (i.e., measurements with time-varying signals) on electrochemical cells and batteries. Current-carrying and voltage-sensing conductor pairs within such cables comprise distributed-parameter two-wire transmission lines which may extend several meters in length. As with all such transmission lines, internally reflected waves can oscillate back and forth at high frequency (hf) whenever the lines are not terminated in their characteristic impedances. Such hf reflected waves, by interacting with measuring circuitry, can seriously degrade low-frequency measurement accuracy. Apparatus is disclosed herein that suppresses hf reflected waves oscillating on Kelvin connecting cables during dynamic measurements of cells and batteries.

Claims

1. Apparatus employing time-varying signals to test an electrochemical cell or battery comprising:

measuring circuitry adapted to couple to said cell or battery with separate current-carrying and voltage-sensing conductors,

a Kelvin cable interposed between said measuring circuitry and said cell or battery, said Kelvin cable comprising a pair of current-carrying conductors and a pair of voltage-sensing conductors; and

,

magnetic core material surrounding a section of said Kelvin cable, said magnetic core material introducing high-frequency attenuation and loss into two-wire transmission lines comprising said pair of current-carrying conductors and said pair of voltage-sensing conductors.

2. Apparatus employing time-varying signals to test an electrochemical cell or battery comprising:

measuring circuitry adapted to couple to said cell or battery with separate current-carrying and voltage-sensing conductors,

a Kelvin cable interposed between said measuring circuitry and said cell or battery, said Kelvin cable comprising a pair of current-carrying conductors and a pair of voltage-sensing conductors; and

,

a bypass capacitor connected directly across said pair of current-carrying conductors, said bypass capacitor providing a high-frequency signal path between said pair of current-carrying conductors.

3. The apparatus of claim 2 wherein said bypass capacitor is connected at an interface between said measuring circuitry and said Kelvin cable.

4. The apparatus of claim 2 wherein said Kelvin cable includes a four-wire cable section and a spaced-apart cable section contacting terminals of said cell/battery, said bypass capacitor being connected at an interface between said four-wire cable section and said spaced-apart cable section.

5. The apparatus of claim 3 wherein said bypass capacitor is at least 1 microfarad in value.

6. Apparatus employing time-varying signals to test an electrochemical cell or battery comprising:

measuring circuitry adapted to couple to said cell or battery with separate current-carrying and voltage-sensing conductors,

a Kelvin cable interposed between said measuring circuitry and said cell or battery, said Kelvin cable comprising a pair of current-carrying conductors and a pair of voltage-sensing conductors; and

,

one or more magnetic cores placed upon said current-carrying conductors, said magnetic cores impeding high-frequency current flow through said pair of current-carrying conductors.

7. The apparatus of claim 6 wherein said magnetic cores are placed at an interface between said measuring circuitry and said Kelvin cable.

8. The apparatus of claim 6 wherein said Kelvin cable includes a four-wire cable section and a spaced-apart cable section contacting terminals of said cell/battery, and said magnetic cores are placed at an interface between said four-wire cable section and said spaced-apart cable section.

9. Apparatus employing time-varying signals to test an electrochemical cell or battery comprising:

measuring circuitry adapted to couple to said cell or battery with separate current-carrying and voltage-sensing conductors,

a Kelvin cable interposed between said measuring circuitry and said cell or battery, said Kelvin cable comprising a pair of current-carrying conductors and a pair of voltage-sensing conductors; and

,

a bypass capacitor connected directly across said pair of voltage-sensing conductors, said bypass capacitor providing a high-frequency signal path between said pair of voltage- sensing conductors.

10. The apparatus of claim 9 wherein said bypass capacitor is connected at an interface between said measuring circuitry and said Kelvin cable.

11. The apparatus of claim 9 wherein said Kelvin cable includes a four-wire cable section and a spaced-apart cable section contacting terminals of said cell/battery, said bypass capacitor being connected at an interface between said four-wire cable section and said spaced-apart cable section.

12. Apparatus employing time-varying signals to test an electrochemical cell or battery comprising:

measuring circuitry adapted to couple to said cell or battery with separate current-carrying and voltage-sensing conductors,

a Kelvin cable interposed between said measuring circuitry and said cell or battery, said Kelvin cable comprising a pair of current-carrying conductors and a pair of voltage-sensing conductors; and

,

one or more magnetic cores placed upon said voltage-sensing conductors, said magnetic cores impeding high-frequency current flow through said pair of voltage-sensing conductors.

13. The apparatus of claim 12 wherein said magnetic cores are placed at an interface between said measuring circuitry and said Kelvin cable.

14. The apparatus of claim 12 wherein said Kelvin cable includes a four-wire cable section and a spaced-apart cable section contacting terminals of said cell/battery, said magnetic cores being placed at an interface between said four-wire cable section and said spaced-apart cable section.

15. Apparatus employing time-varying signals to test an electrochemical cell or battery comprising:

measuring circuitry adapted to couple to said cell or battery with separate current-carrying and voltage-sensing conductors,

a Kelvin cable interposed between said measuring circuitry and said cell or battery, said Kelvin cable comprising a pair of current-carrying conductors and a pair of voltage-sensing conductors, said pair of voltage-sensing conductors possessing a particular characteristic impedance value; and

,

a blocking capacitor and a resistor connected in series across said pair of voltage-sensing conductors at an interface between said measuring circuitry and said Kelvin cable, said resistor having a value essentially equal to said particular characteristic impedance value.

16. Apparatus employing time-varying signals to test an electrochemical cell or battery comprising:

measuring circuitry adapted to couple to said cell or battery with separate current-carrying and voltage-sensing conductors,

a four-wire cable section interfaced with said measuring circuitry, said four-wire cable section comprising a pair of current-carrying conductors and a pair of voltage-sensing conductors, said pair of voltage-sensing conductors possessing a particular characteristic impedance value,

a spaced-apart cable section interposed between said four-wire cable section and said cell or battery, said spaced-apart cable section possessing a pair of voltage-sensing conductors that separately contact positive and negative terminals of said cell or battery; and

,

one or more resistances connected in series with said voltage sensing conductors in said spaced-apart cable section, said resistances being essentially equal in sum value to said particular characteristic impedance value.

17. (canceled)