Apparatus and method for diagnosing state of battery

1. An apparatus for diagnosing a state of a battery pack, the battery pack having a battery module with at least one battery cell, the apparatus comprising:

a charging and discharging assembly configured to charge or discharge the battery module;

a measurer configured to measure a current of the battery module at every predetermined period during a cycle in which the battery module is charged or discharged; and

a controller configured to:

receive a measurement value for the current of the battery module from the measurer, estimate a state of charge (SOC) of the battery module during the cycle based on the received measurement value,

calculate a change rate of the estimated SOC, and

determine whether a defect occurs in the battery module based on a comparison result between the calculated change rate of the SOC and a preset reference change rate,

wherein the controller is configured to calculate an instant change rate of the estimated SOC, determine a plurality of peaks in the calculated instant change rate, select a peak closest to an intermediate time point of the cycle among the plurality of determined peaks as a target peak, and determine whether the defect occurs in the battery module by comparing the selected target peak with a reference peak of the preset reference change rate.

2. The apparatus for diagnosing a state of a battery according to claim 1 ,

wherein the step of calculating a change rate of the estimated SOC includes calculating the instant change rate of the estimated SOC, and

wherein the step of determining whether the defect occurs in the battery modules includes determining whether the defect occurs in the battery module based on a comparison result between the calculated instant change rate and the preset reference change rate corresponding thereto at the same time point.

3. The apparatus for diagnosing a state of a battery according to claim 2 ,

wherein the battery module includes a plurality of battery cells, and

wherein, in response to the calculated instant change rate being greater than the preset reference change rate, the controller determines that the defect occurs in at least one of the plurality of battery cells included in the battery module.

4. The apparatus for diagnosing a state of a battery according to claim 1 ,

wherein the battery module is provided in plural, and

wherein the controller is configured to:

calculate the instant change rate of the SOC for each of the plurality of battery modules,

select a target peak in the instant change rate of each of the plurality of battery modules, and

determine a relative degree of defect occurrence of the plurality of battery modules by comparing magnitudes of the plurality of selected target peaks.

5. The apparatus for diagnosing a state of a battery according to claim 4 ,

wherein the plurality of target peaks are peaks closest to an intermediate time point of a charging and discharging cycle of corresponding battery modules and are locatable at different time points.

6. The apparatus for diagnosing a state of a battery according to claim 4 ,

wherein the controller is configured to determine that the degree of defect occurrence of each battery module is greater as a magnitude of the corresponding target peak among the plurality of selected target peaks is greater.

7. A battery pack, comprising the apparatus for diagnosing a state of a battery according to claim 1 .

8. The apparatus for diagnosing a state of a battery according to claim 1 , wherein the SOC of the battery module is estimated using an ampere counting method.

9. The apparatus for diagnosing a state of a battery according to claim 1 , wherein the battery module includes a plurality of battery cells, and

wherein the current is measured for the battery module as a whole.

10. The apparatus for diagnosing a state of a battery according to claim 1 , wherein each peak is a point at which the calculated instant change rate increases and then decreases over a time period.

11. The apparatus for diagnosing a state of a battery according to claim 1 , wherein the controller is configured to determine that the defect occurs in the battery module when the selected target peak is greater than the reference peak.

12. A method for diagnosing a state of a battery pack, the battery pack having a battery module with at least one battery cell, the method comprising:

a charging and discharging step of charging or discharging the battery module;

a measuring step of measuring a current of the battery module at every predetermined period during a cycle in which the battery module is charged or discharged;

a state of charge (SOC) estimating step of estimating a SOC of the battery module during the cycle based on the measurement value measured in the measuring step;

a SOC change rate calculating step of calculating a change rate of the SOC estimated in the SOC estimating step; and

a battery module defect determining step of determining whether a defect occurs in the battery module based on a comparison result between the change rate calculated in the change rate calculating step and a preset reference change rate,

wherein the battery module defect determining step further includes:

calculating an instant change rate of the estimated SOC,

determining a plurality of peaks in the calculated instant change rate,

selecting a peak closest to an intermediate time point of the cycle among the plurality of determined peaks as a target peak, and

determining whether the defect occurs in the battery module by comparing the selected target peak with a reference peak of the preset reference change rate.

13. The method for diagnosing a state of a battery according to claim 12 ,

wherein the battery module is provided in plural,

wherein the SOC change rate calculating step includes:

an instant change rate calculating step of calculating an instant change rate of the SOC for each of the plurality of battery modules,

wherein the battery module defect determining step includes:

a target peak selecting step of selecting the target peak in the instant change rate of each of the plurality of battery modules calculated in the change rate calculating step; and

a relative defect determining step of determining a relative degree of defect occurrence of the plurality of battery modules by comparing magnitudes of the plurality of selected target peaks.

14. The method for diagnosing a state of a battery according to claim 13 , wherein the battery module defect determining step includes determining that a degree of defect occurrence of each battery module is greater as a magnitude of the corresponding target peak among the plurality of selected target peaks is greater.

15. The method for diagnosing a state of a battery according to claim 12 , wherein the SOC of the battery module is estimated using an ampere counting method.

16. The method for diagnosing a state of a battery according to claim 12 , wherein the battery module includes a plurality of battery cells, and

wherein the current is measured for the battery module as a whole.

17. The method for diagnosing a state of a battery according to claim 12 , wherein each peak is a point at which the calculated instant change rate increases and then decreases over a time period.

18. The method for diagnosing a state of a battery according to claim 12 , wherein the battery module defect determining step further includes determining that the defect occurs in the battery module when the selected target peak is greater than the reference peak.