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Cell balancing apparatus and method using a voltage variation pattern of each cell to estimate an open circuit voltage value for each cell

  • US 9,287,723 B2
  • Filed: 12/09/2009
  • Issued: 03/15/2016
  • Est. Priority Date: 08/08/2008
  • Status: Active Grant
First Claim
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1. A cell balancing apparatus using a voltage variation pattern of a battery cell, which balances a state of charge (SOC) of a plurality of cells in a battery, the cell balancing apparatus comprising:

  • an open circuit voltage (OCV) estimating means for measuring a voltage of each cell in the battery and estimating an OCV of each cell using a voltage variation pattern of each cell defined by three output voltages Vn, Vn-1 and Vn-2; and

    a cell balancing means for balancing an SOC of each cell by selecting a target cell for balancing through a comparison of the estimated OCV of each cell and controlling a balancing circuit corresponding to the selected cell,the OCV estimating means comprising;

    a voltage measuring unit for measuring the voltage of each cell;

    a temperature measuring unit for measuring a temperature of each cell;

    a data storing unit for periodically receiving the voltage and temperature of each cell from the voltage measuring unit and the temperature measuring unit and storing the voltage and temperature in a memory unit;

    an OCV variation estimating unit for estimating a present OCV variation of each cell by calculating an OCV variation of each cell Δ

    OCVn(k) from the voltage variation pattern including a present voltage and a past voltage, stored in the memory unit, using a mathematical model that defines a correlation between the output voltage variation pattern and the OCV variation, and reflecting a correction factor F(T) corresponding to the temperature of each cell on the calculated OCV variation of each cell; and

    an OCV estimating unit for estimating a present OCV of each cell by reflecting the calculated OCV variation of each cell on a previous OCV of each cell,wherein
    Δ

    OCVn(k)=OCVn(k)−

    OCVn-1(k)=G(V

    F(T)=[Vn

    V
    n-1

    g
    (Vn,Vn-1,Vn-2

    F(T),wherein g(Vn, Vn

    1, Vn

    2) is a relative ratio of a previous output voltage variation to a present output voltage variation, andwherein “

    n”

    is an order index of estimating an OCV variation, and “

    k”

    is an order index of a cell.

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