# US 12,119,695 B2 · Device and method for detecting poor battery cell

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- Number: US 12,119,695 B2
- Document ID: US12119695B2
- Status: Granted
- Kind: B2
- Application number: 17/103,221
- Filed: 2020-11-24
- Published: 2021-06-24
- Granted: 2024-10-15
- Earliest claimed: 2019-12-19
- Assignees: LG Energy Solution, Ltd.
- Applicants: LG Chem, Ltd.
- Inventors: Bo Mi Lim
- Web page: https://patentgrep.com/patent/US12119695B2

## CPC

- G01R 31/396: Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
- H02J 7/84: Control of state of health [SOH]
- G01R 31/3648: {comprising digital calculation means, e.g. for performing an algorithm}
- G01R 31/3835: involving only voltage measurements
- H01M 10/441: {for several batteries or cells simultaneously or sequentially}
- H01M 10/46: Accumulators structurally combined with charging apparatus (circuits for charging H02J7/00)
- H01M 10/482: {for several batteries or cells simultaneously or sequentially}
- H02J 7/50: acting upon multiple batteries simultaneously or sequentially
- H02J 7/82: Control of state of charge [SOC]
- H02J 7/96: in response to battery voltage
- Y02E 60/10: Energy storage using batteries
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)
- H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

An ESS capable of detecting a defective battery cell, the ESS in accordance with an exemplary embodiment, may include a plurality of battery cells, and a control unit for controlling the charge/discharge of the ESS, wherein the control unit includes an SOC calculation unit for calculating the SOC of the ESS, a voltage measurement unit for measuring the voltage of each of the plurality of battery cells, and a poor battery cell detection unit for detecting a defective battery cell from the voltages measured in the voltage measurement unit.

## Claims

### Claim 1

An energy storage system (ESS) comprising:
a plurality of battery cells;
a control unit programmed to control charging and discharging of the ESS, wherein the control unit includes:
an SOC calculation unit for calculating a state of charge (SOC) of the ESS;
a voltage measurement sensor for measuring voltage of each of the plurality of battery cells; and
a poor battery cell detection unit for detecting a defective battery cell among the plurality of battery cells from the voltages measured by the voltage measurement sensor, the poor battery cell detection unit including:
a voltage difference value calculation unit for calculating, when a SOC value calculated by the SOC calculation unit is equal to or less than a predetermined SOC value of 10%, a difference between a minimum voltage and a maximum voltage measured by the voltage measurement sensor;
a minimum voltage battery cell detection unit for detecting a battery cell among the plurality of battery cells having the minimum voltage when the difference between the minimum voltage and the maximum voltage is equal to or greater than a predetermined first reference value; and
a correlation value calculation unit for calculating a correlation value for voltage values of only the detected minimum voltage battery cell for a predetermined period of time,
wherein the poor battery cell detection unit determines whether the minimum voltage battery cell with the minimum voltage is defective when the correlation value calculated by the correlation value calculation unit is equal to or greater than a predetermined second reference value,
wherein the correlation value calculation unit calculates a first correlation value by performing correlation analysis on voltage values when the SOC value calculated by the SOC calculation unit is equal to or less than the predetermined SOC value among voltage values recorded in the detected battery cell having the minimum voltage for the predetermined period of time, using the following Equation:
ρ
=
∑
XY
-
∑
X
⁢
∑
Y
N
(
∑
X
2
-
(
∑
X
)
2
N
)
⁢
(
∑
Y
2
-
(
∑
Y
)
2
N
)
where ρ is the first correlation value, where X is voltage, Y is time and N is the number of cells,
wherein the first correlation value is between −1, which represents a perfect negative correlation and +1, which represents a perfect positive correlation,
wherein the poor battery cell detection unit determines that the battery cell having the minimum voltage is defective when the first correlation value is equal to or greater than the predetermined second reference value and a second correlation value is equal to or less than a predetermined third reference value,
wherein the first correlation value is different than the second correlation value, and
wherein the predetermined first reference value is a value set based on an expected error rate in the calculation of the SOC.

### Claim 2 (depends on 1)

The ESS of claim 1, wherein the correlation value calculation unit calculates the second correlation value by performing correlation analysis on the voltage value of the detected battery cell having the minimum voltage and voltage values of remaining cells except for the detected minimum voltage battery cell.

### Claim 3 (depends on 1)

The ESS of claim 1, wherein the predetermined first reference value is less than or equal to 0.6 V.

### Claim 4 (depends on 1)

The ESS of claim 1, wherein the predetermined second reference value is approximately 0.75.

### Claim 5

A method for detecting a poor battery cell in energy storage system (ESS) comprising a plurality of battery cells, the method comprising:
a voltage measuring step including measuring voltage of each of the plurality of battery cells; and
a poor battery cell detecting step including:
detecting a defective battery cell among the plurality of battery cells based on the measured voltage of each of the battery cells;
a voltage difference value calculating step including calculating a difference between a maximum voltage and a minimum voltage by detecting a maximum voltage and a minimum voltage of each of the battery cells when a SOC of the ESS is equal to or less than a predetermined SOC value of 10%;
a minimum voltage battery cell detecting step including detecting a battery cell among the plurality of battery cells having the minimum voltage value when the calculated voltage difference value is equal to or greater than a predetermined first reference value;
a correlation value calculating step including calculating a correlation value for only the detected battery cell having the minimum voltage; and
a defect determining step including determining whether battery cell production is defective when the calculated correlation value is equal to or greater than a predetermined second reference value,
wherein the correlation value calculating step comprises a first correlation value calculating step including calculating a first correlation value by performing correlation analysis on voltage values when the SOC value is equal to or less than the predetermined SOC value among voltage values recorded in the detected battery cell having the minimum voltage for a predetermined period of time, using the following Equation:
ρ
=
∑
XY
-
∑
X
⁢
∑
Y
N
(
∑
X
2
-
(
∑
X
)
2
N
)
⁢
(
∑
Y
2
-
(
∑
Y
)
2
N
)
where ρ is the first correlation value, where X is voltage, Y is time and N is the number of cells,
wherein the first correlation value is between −1, which represents a perfect negative correlation and +1, which represents a perfect positive correlation,
wherein the defect determining step detects the battery cell having the minimum voltage as the defective battery cell when the first correlation value is equal to or greater than the predetermined second reference value and a second correlation value is equal to or less than a predetermined third reference value,
wherein the first correlation value is different than the second correlation value, and
wherein the predetermined first reference value is a value set based on an expected error rate in calculating the SOC.

### Claim 6 (depends on 5)

The method of claim 5, wherein the correlation value calculating step comprises a second correlation value calculating step including calculating the second correlation value by performing correlation analysis on the voltage values of the detected battery cell having the minimum voltage and voltage values of remaining cells except for the battery cell having the minimum voltage.

### Claim 7 (depends on 5)

The method of claim 5, wherein the predetermined first reference value is less than or equal to 0.6 V.

### Claim 8 (depends on 5)

The method of claim 5, wherein the predetermined second reference value is approximately 0.75.