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Method and apparatus for measurement of electrochemical cell and battery impedances

  • US 20010035756A1
  • Filed: 12/22/2000
  • Published: 11/01/2001
  • Est. Priority Date: 01/03/2000
  • Status: Active Grant
First Claim
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1. An apparatus for measuring impedance in an electrochemical cell comprising:

  • a current generator for producing an input current signal Ii along a current signal path in a current divider network;

    said current divider network having at least a sensing current path and a battery current path, said sensing and battery current paths being in parallel to each other, each of said sensing and battery current paths also being in series with said current signal path, said current signal, sensing, and battery paths interconnecting with each other at a current dividing connector and at a current converging connector;

    said sensing current path having a measurable sensing impedance Zs located along said sensing current path, a connector-wire impedance Z1 between said current dividing connector and said sensing impedance Zs, and a connector-wire impedance Z3 between said sensing impedance Zs and said current converging connector, wherein a portion Is of current signal Ii flows through said sensing current path;

    said battery current path having a battery impedance Zb located along said battery current path, a connector-wire impedance Z2 between said current dividing connector and said battery impedance Zb, and a connector-wire-capacitor impedance Z4 between said battery impedance Zb and said current converging connector, wherein a portion Ib of current signal Ii flows through said battery path;

    a DC-blocking capacitor in series with said battery impedance Zb and located along said battery current path to prevent said battery from discharging current through said sensing impedance Zs;

    said sensing current path also having a magnetic field sensor with a coupling attached thereto for measuring the magnitude and phase of Is, thereby permitting mathematical determination of the value of Zb.

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