Battery diagnosis apparatus, battery diagnosis method and energy storage system

1. A battery diagnosis apparatus, comprising:

a voltage measurer configured to measure a cell voltage of each of first to n th battery cells of a battery, wherein n is a natural number of 2 or greater; and

a processor operably coupled to the voltage measurer and to a switch of the battery,

wherein the processor is configured to:

determine first to n th average cell voltages for a first rest period associated with the first to n th battery cells in a one-to-one relationship, based on the cell voltage of each battery cell measured a first number of times for the first rest period, wherein the first rest period is from a first time point to a second time point,

determine first to n th average cell voltages for a second rest period associated with the first to n th battery cells in a one-to-one relationship, based on the cell voltage of each battery cell measured a second number of times for the second rest period, wherein the second rest period is from a third time point to a fourth time point, and the third time point is later than the second time point, and is a time point at which a threshold time has passed since the first time point,

diagnose a fault of each of the first to n th battery cells based on the first to n th average cell voltages for the first rest period and the first to n th average cell voltages for the second rest period, and

execute a safety operation of controlling the switch of the battery to an OFF state, in response to diagnosing the fault.

2. The battery diagnosis apparatus according to claim 1 , wherein the first time point is a time point at which the first to n th battery cells is changed from a cycle state to a rest state.

3. The battery diagnosis apparatus according to claim 1 , wherein the processor is configured to determine the first to n th average cell voltages for the first rest period using the following Equation 1:

V

k

⁢

_

⁢

1

=

1

i

×

∑

x

=

1

i

V

k

[

x

]

<

Equation

⁢

1

>

wherein k is a natural number that is equal to or less than n, i is the first number of times, x is a natural number that is equal to or less than i, V k [x] is the cell voltage of the k th battery cell measured at the x th time within the first rest period, and V k_1 is the k th average cell voltage for the first rest period.

4. The battery diagnosis apparatus according to claim 3 , wherein the processor is configured to determine the first to n th average cell voltages for the second rest period using the following Equation 2:

V

k

⁢

_

⁢

2

=

1

j

×

∑

y

=

1

j

V

k

[

y

]

<

Equation

⁢

2

>

wherein k is a natural number that is equal to or less than n, j is the second number of times, y is a natural number that is equal to or less than j, V k [y] is the cell voltage of the k th battery cell measured at the y th time within the second rest period, and V k_2 is the k th average cell voltage for the second rest period.

5. The battery diagnosis apparatus according to claim 4 , wherein the processor is configured to:

determine a first reference voltage based on the first to n th average cell voltages for the first rest period, and

determine a second reference voltage based on the first to n th average cell voltages for the second rest period.

6. The battery diagnosis apparatus according to claim 5 , wherein the processor is configured to determine first to n th reference values associated with the first to n th battery cells in a one-to-one relationship, using the following Equation 3:

R

k

=

V

k

⁢

_

⁢

1

-

V

k

⁢

_

⁢

2

V

ref

⁢

_

⁢

1

-

V

ref

⁢

_

⁢

2

<

Equation

⁢

3

>

wherein k is a natural number that is equal to or less than n, V ref_1 is the first reference voltage, V ref_2 is the second reference voltage, and R k is the k th reference value.

7. The battery diagnosis apparatus according to claim 6 , wherein the processor is configured to diagnose that the k th battery cell is faulty when the k th reference value is equal to or larger than a predetermined threshold diagnosis value that is larger than 1.

8. The battery diagnosis apparatus according to claim 6 , wherein the processor is configured to:

determine first to n th diagnosis values based on the maximum capacity of each of the first to n th battery cells, each diagnosis value being larger than 1, and

diagnose that the k th battery cell is faulty when the k th reference value is equal to or larger than the k th diagnosis value.

9. The battery diagnosis apparatus according to claim 8 , wherein the processor is configured to increase the k th diagnosis value as the maximum capacity of the k th battery cell reduces.

10. The battery diagnosis apparatus according to claim 5 , wherein the processor is configured to determine first to n th reference values associated with the first to n th battery cells in a one-to-one relationship, using the following Equation 4:

R

k

=

V

ref

⁢

_

⁢

2

-

V

k

⁢

_

⁢

2

V

ref

⁢

_

⁢

1

-

V

k

⁢

_

⁢

1

<

Equation

⁢

4

>

wherein k is a natural number that is equal to or less than n, V ref_1 is the first reference voltage, V ref_2 is the second reference voltage, and R k is the k th reference value.

11. The battery diagnosis apparatus according to claim 1 , wherein the processor is configured to determine the threshold time based on an average maximum capacity of the first to n th battery cells.

12. The battery diagnosis apparatus according to claim 11 , wherein the processor is configured to reduce the threshold time as the average maximum capacity reduces.

13. An energy storage system comprising the battery diagnosis apparatus according to claim 1 .

14. A battery diagnosis method that is executable by the battery diagnosis apparatus according to claim 1 , the battery diagnosis method comprising:

determining, via the processor, first to n th average cell voltages for a first rest period associated with first to n th battery cells of a battery in a one-to-one relationship, respectively based on cell voltages of the first to n th battery cells measured a first number of times for the first rest period, wherein the first rest period is from a first time point to a second time point, and n is a natural number of 2 or greater;

determining, via the processor, first to n th average cell voltages for a second rest period associated with the first to n th battery cells in a one-to-one relationship, based on a cell voltage of each battery cell measured a second number of times for the second rest period, wherein the second rest period is from a third time point to a fourth time point, and the third time point is later than the second time point and is a time point at which a threshold time has passed since the first time point;

diagnosing, via the processor, a fault of each of the first to n th battery cells based on the first to n th average cell voltages for the first rest period and the first to n th average cell voltages for the second rest period; and

executing, via the processor, a safety operation of controlling a switch of the battery to an OFF state, in response to diagnosing the fault.