Battery diagnosis apparatus, battery pack, electric vehicle, and battery diagnosis method
A battery diagnosis apparatus includes a battery monitor to detect a voltage of each of a plurality of battery cells included in a battery module; and a control circuit to determine a latest value of a first voltage deviation indicating a difference between a voltage behavior of each battery cell and an average voltage behavior of the plurality of battery cells over a relaxation period from a start time of a resting event.
1 . A battery diagnosis apparatus, comprising:
a battery monitor configured to detect a voltage of each of a plurality of battery cells included in a battery module; and
a control circuit of an electrical vehicle configured to:
determine a latest value of a first voltage deviation indicating a difference between a voltage behavior of a battery cell of the plurality of battery cells and an average voltage behavior of the plurality of battery cells over a relaxation period from a start time of a resting event in which the battery module transitions from charging to resting,
when a total number of times the resting event has taken place is equal to or larger than a reference number of times;
determine a latest value of a second voltage deviation of the battery cell, wherein the second voltage deviation corresponds to the latest value of the first voltage deviation applied to a smoothing algorithm;
determine a latest value of a third voltage deviation of the battery cell indicating a first difference between the latest value of the first voltage deviation and the latest value of the second voltage deviation;
determine a latest value of a fourth voltage deviation of the battery cell indicating a second difference between the latest value of the third voltage deviation and a previous value of the third voltage deviation;
determine a latest value of a threshold deviation of the battery cell using a dispersion of a time series of the fourth voltage deviation having a predetermined size; and
determine whether the battery cell has a micro short circuit based on a comparison of the latest value of the third voltage deviation with the latest value of the threshold deviation.
2 . The battery diagnosis apparatus according to claim 1 , wherein, for each battery cell, the voltage behavior of the battery cell indicates an average of a predetermined number of detected voltages of the battery cell over the relaxation period from the start time of the resting event.
3 . The battery diagnosis apparatus according to claim 1 , wherein the smoothing algorithm is a moving average filter, and
wherein the reference number of times is equal to or greater than a size of the moving average filter.
4 . The battery diagnosis apparatus according to claim 1 , wherein the dispersion is a standard deviation.
5 . The battery diagnosis apparatus according to claim 1 , wherein the control circuit is configured to determine, for each of the plurality of battery cells, the latest value of the threshold deviation by multiplying the dispersion by a predetermined margin constant.
6 . The battery diagnosis apparatus according to claim 1 , wherein the control circuit is configured to,
for each of the plurality of battery cells, increase a factor associated with the battery cell by a first value when the latest value of the third voltage deviation is equal to or smaller than the latest value of the threshold deviation; and
determine that at least one of the plurality of battery cells has the micro short circuit when the factor associated with the at least one of the plurality of battery cells reaches a threshold.
7 . The battery diagnosis apparatus according to claim 6 , wherein the control circuit is configured to decrease, the factor associated with the at least one of the plurality of battery cells by a second value when the latest value of the third voltage deviation is larger than the latest value of the threshold deviation.
8 . A battery pack comprising the battery diagnosis apparatus according to claim 1 .
9 . An electric vehicle comprising the battery pack according to claim 8 .
10 . A battery diagnosis method, comprising:
detecting, by a battery monitor, a voltage of each of a plurality of battery cells included in a battery module;
determining, by a control circuit of an electrical vehicle-processor, a latest value of a first voltage deviation indicating a difference between a voltage behavior of a battery cell of the plurality of battery cells and an average voltage behavior of the plurality of battery cells over a relaxation period from a start time of a resting event in which a battery module including the plurality of battery cells transitions from charging to resting,
when a total number of times the resting event has taken place is equal to or larger than a reference number of times;
determining, by the control circuit, a latest value of a second voltage deviation of the battery cell, wherein the second voltage deviation corresponds to the latest value of the first voltage deviation applied to a smoothing algorithm-;
determining, by the control circuit, a latest value of a third voltage deviation of the battery indicating a first difference between the latest value of the first voltage deviation and the latest value of the second voltage deviation, determining, by the control circuit, a latest value of a fourth voltage deviation of the battery cell indicating a second difference between the latest value of the third voltage deviation and a previous value of the third voltage deviation;
determining, by the control circuit, a latest value of a threshold deviation of the battery cell using a dispersion of a time series of the fourth voltage deviation having a predetermined size; and
determining, by the control circuit, whether the battery cell has a micro short circuit based on a comparison of the latest value of the third voltage deviation with the latest value of the threshold deviation.
11 . The battery diagnosis method according to claim 10 , wherein, for each battery cell, the voltage behavior of the battery cell indicates an average of a predetermined number of detected voltages of the battery cell over the relaxation period from the start time of the resting event.
12 . The battery diagnosis method according to claim 10 , wherein the smoothing algorithm is a moving average filter, and wherein the reference number of times is equal to or greater than a size of the moving average filter.
13 . The battery diagnosis method according to claim 10 , wherein the dispersion is a standard deviation.
14 . The battery diagnosis method according to claim 10 , wherein the latest value of the threshold deviation is equal to a multiplication of the dispersion by a predetermined margin constant.
15 . The battery diagnosis method according to claim 10 , further comprising performing, by the control circuit, a protection operation in response to determining the battery cell has the micro short circuit, wherein the protection operation includes turning off a relay connected in series to the plurality of battery cells through a power path connecting the plurality of battery cells to an electrical load.