US 9,287,723 B2Granted

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

AssigneeLG Chem, Ltd.

InventorsJung-Soo Kang, Do-Youn Kim

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Abstract

Disclosed is a cell balancing apparatus and method using a voltage variation pattern of a battery cell, which measures voltage of each cell, estimates OCV or SOC of each cell using a voltage variation pattern of each cell including a present voltage and a past voltage, and eliminates a deviation in OCV or SOC between the cells through comparison of the estimated OCV or SOC of each cell. In estimating the OCV of each cell, an output voltage error due to IR drop is corrected. Thus, SOC of each cell may be accurately estimated. And, an accurate estimation of SOC may render substantial elimination for a SOC deviation of each cell. Furthermore, SOC estimating using an output voltage leads to an active cell balancing even during charge and discharge of battery, thereby minimizing an SOC deviation of each cell.

Claims19

Dependent claims

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 ΔOCVn(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
ΔOCVn(k)=OCVn(k)−OCVn-1(k)=G(V)×F(T)=[Vn−Vn-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, and
wherein “n” is an order index of estimating an OCV variation, and “k” is an order index of a cell.

11 more elements

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 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;
an SOC estimating means for estimating an SOC of each cell from the OCV of each cell;
and
a cell balancing means for balancing the SOC of each cell by selecting a target cell for balancing through a comparison of the estimated SOC 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 ΔOCVn(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
ΔOCVn(k)=OCVn(k)−OCVn-1(k)=G(V)×F(T)=[Vn−Vn-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, and
wherein “n” is an order index of estimating an OCV variation, and “k” is an order index of a cell.

12 more elements

A cell balancing method 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 method comprising:

measuring a voltage of each cell in the battery and estimating an open circuit voltage (OCV) of each cell using a voltage variation pattern of each cell defined by three output voltages Vn, Vn-1 and Vn-2;
and
balancing the SOC of the plurality of cells through a comparison of the estimated OCV of each cell,
the estimating the OCV comprising:
measuring the voltage and a temperature of each cell;
calculating an OCV variation ΔOCVn(k) of each cell from the voltage variation pattern using a mathematical model that defines a correlation between the output voltage variation pattern and the OCV variation;
estimating a present OCV variation of each cell by reflecting a correction factor F(T) corresponding to the temperature of each cell on the calculated OCV variation of each cell;
and
estimating a present OCV of each cell by reflecting the calculated OCV variation of each cell on a previous OCV of each cell,
wherein
ΔOCVn(k)=OCVn(k)−OCVn-1(k)=G(V)×F(T)=[Vn−Vn-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, and
wherein “n” is an order index of estimating an OCV variation, and “k” is an order index of a cell.

10 more elements

A cell balancing method 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 method comprising:

measuring a voltage of each cell in the battery and estimating an open circuit voltage (OCV) of each cell using a voltage variation pattern defined by three output voltages Vn, Vn-1 and Vn-2;
estimating an SOC of each cell from the OCV of each cell;
and
balancing the SOC of the plurality of cells through a comparison of the estimated SOC of each cell,
the estimating the OCV comprising:
measuring the voltage and a temperature of each cell;
calculating an OCV variation ΔOCVn(k) of each cell from the voltage variation pattern using a mathematical model that defines a correlation between the output voltage variation pattern and the OCV variation;
estimating a present OCV variation of each cell by reflecting a correction factor F(T) corresponding to the temperature of each cell on the calculated OCV variation of each cell;
and
estimating a present OCV of each cell by reflecting the calculated OCV variation of each cell on a previous OCV of each cell,
wherein
ΔOCVn(k)=OCVn(k)−OCVn-1(k)=G(V)×F(T)=[Vn−Vn-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, and
wherein “n” is an order index of estimating an OCV variation, and “k” is an order index of a cell.

11 more elements

Dependencies are inferred from the claim text.

Facts

Application: 12/634,310Filed 9 Dec 2009 · continuation in part
Priority: KR 10-2008-00781898 Aug 2008
Published: US 2010/0085009 A18 Apr 2010
Granted: 15 Mar 2016
Term ends: Not estimatedThe source records don’t support an estimate.

Classification12 codes

H02J 7/56
For charge balancing, e.g. equalisation of charge between batteries: active balancing, e.g. using capacitor-based, inductor-based or DC-DC converters
H01M 10/482
Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte:…
H02J 7/54
For charge balancing, e.g. equalisation of charge between batteries: passive balancing, e.g. using resistors or parallel MOSFETs
G01R 31/3835
Arrangements for monitoring battery or accumulator variables, e.g. SoC: involving only voltage measurements