Battery diagnostic device and battery diagnostic method

Abstract

The battery diagnostic device includes an information acquisition unit that acquires current data of the battery cell, and a controller that sets a first point in time and a second point in time that is a predetermined time after the first point in time using a time interval acquired based on the AC component of the current data acquired during a constant voltage charging section of the battery cell, and determines the state of the battery cell based on the current values ​​at the first and second points in time.

Description

[Technical Field]

[0001] The present invention claims the benefit of priority based on Korean Patent Application No. 10-2023-0028776, filed on March 3, 2023, the entire contents of which are incorporated herein by reference. The embodiments disclosed herein relate to a battery diagnostic device and a battery diagnostic method. [Background technology]

[0002] In recent years, the widespread use of portable devices such as smartphones and laptop computers, transportation methods such as electric cars, electric scooters, and electric motorcycles, and devices for stable power supply and management such as energy storage systems (ESS) has led to increased interest in batteries and more active development.

[0003] A battery is a component for supplying power to a device, system, etc. In this case, the battery may be used in the form of a single secondary battery acting as a battery cell to supply power alone, or in the form of multiple secondary batteries constituting a single battery module or a single battery bank to supply power.

[0004] However, batteries can become defective due to various reasons. For example, lithium (Li) ions may precipitate inside the battery, and current may be supplied to the precipitated lithium, causing the battery to generate heat. Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the embodiments disclosed in this specification is to provide a battery diagnostic device and a battery diagnostic method for diagnosing a battery.

[0006] The technical problems of the embodiments described in this specification are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those of ordinary skill in the art to which the present invention pertains from the following description. [Means for solving the problem]

[0007] A battery diagnostic device according to one embodiment disclosed in this specification includes an information acquisition unit that acquires current data of a battery cell, and a controller that acquires the current data during a constant voltage charging interval of the battery cell, sets a first point in time at which the current data is acquired and a second point in time at which the current data is acquired after a predetermined time has elapsed since the first point in time, and determines the state of the battery cell based on the current values ​​at the first point in time and the second point in time.

[0008] According to one embodiment, the controller may determine that the battery cell is an abnormal battery cell if the current value at the second time point is greater than the current value at the first time point.

[0009] According to one embodiment, the controller may change the first and second time points while maintaining the time interval between the first and second time points, and compare the current value at the first time point with the current value at the second time point. According to one embodiment, the abnormal battery cell may include a battery cell in which lithium (Li) is precipitated inside the battery cell.

[0010] According to one embodiment, the controller may separate the current data into a DC component and an AC component using a moving average of the current data. According to one embodiment, the controller can remove the DC component from the current data to extract the AC component.

[0011] According to one embodiment, the controller can calculate a standard deviation of the AC component and set the time interval between the first time point and the second time point based on the standard deviation. According to an embodiment, the battery diagnostic device may further include a storage unit that stores current data of the battery cell measured by the information acquisition unit.

[0012] A battery diagnostic method according to one embodiment disclosed in this specification includes the steps of acquiring current data of a battery cell during a constant voltage charging interval of the battery cell, setting a first point in time and a second point in time that is a predetermined time after the first point in time using a time interval acquired based on the AC component of the current data, and determining the state of the battery cell based on the current values ​​at the first point in time and the second point in time.

[0013] According to one embodiment, the step of determining the state of the battery cell may be a step of determining the battery cell as an abnormal battery cell if the current value at the second time point is greater than the current value at the first time point. According to one embodiment, the abnormal battery cell may include a battery cell in which lithium (Li) is precipitated inside the battery cell.

[0014] According to one embodiment, the step of determining the state of the battery cell may include the steps of generating a graph based on the current data, the graph having a first axis representing time and a second axis representing current value, and changing the first and second points in time while maintaining the time interval between the first and second points in time defined in the graph, and comparing the current value at the first point in time with the current value at the second point in time.

[0015] According to an embodiment, setting the time interval may include dividing the current data into a DC component and an AC component using a moving average of the current data.

[0016] According to an embodiment, the step of setting the time interval may include, after the dividing step, removing the DC component from the current data to extract the AC component.

[0017] According to one embodiment, the step of setting the time interval may include, after the step of extracting the AC component, calculating a standard deviation of the AC component, and setting the time interval between the first time point and the second time point based on the standard deviation. Specific details of other embodiments are included in the detailed description and drawings. [Effects of the Invention]

[0018] According to the battery diagnostic device and battery diagnostic method according to the embodiments disclosed in this specification, the state of the battery can be diagnosed based on the current data of the battery.

[0019] According to the battery diagnostic device and battery diagnostic method of the embodiments disclosed in this specification, by diagnosing lithium deposition inside a battery, it is possible to detect abnormal batteries early and prevent battery heat generation and fires. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a block diagram illustrating a battery pack according to one embodiment disclosed herein. [Figure 2] 1 is a diagram illustrating a battery diagnostic device according to an embodiment disclosed in this specification. [Figure 3] 1 is a graph of current over time for a battery cell generated by a battery diagnostic device according to an embodiment disclosed herein. [Figure 4] 4 is a diagram showing current data in region A of FIG. 3 together with a moving average line of the current data. [Figure 5] FIG. 5 is a diagram showing the difference between the current data and the moving average line in FIG. 4. [Figure 6] 1 is a flowchart illustrating a battery diagnostic method according to one embodiment disclosed herein. [Figure 7] 7 is a flowchart specifically showing the operation of determining the state of the battery cell based on the current values ​​at the first and second points in time in FIG. 6. [Figure 8]FIG. 1 illustrates a computing system for implementing a battery diagnostic method according to one embodiment disclosed herein. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, the embodiments disclosed herein will be described in detail with reference to the accompanying drawings. When assigning reference numerals to components in each drawing, it should be noted that the same reference numerals are assigned to the same components as long as possible when they appear in other drawings. Furthermore, when describing the embodiments disclosed herein, if a detailed description of related known structures or functions is deemed to hinder understanding of the embodiments disclosed herein, such detailed description will be omitted.

[0022] When describing components of the embodiments disclosed herein, terms such as "first," "second," etc. may be used. Such terms are merely used to distinguish the component from other components and do not limit the nature, order, or sequence of the components. Furthermore, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art to which the embodiments disclosed herein belong. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with the context of the relevant art, and should not be interpreted in an idealized or overly formal sense unless expressly defined in this application.

[0023] FIG. 1 is a block diagram illustrating a battery pack according to one embodiment disclosed herein. Referring to FIG. 1, a battery control system including a battery pack 1 according to one embodiment disclosed in this specification and a host controller 2 included in the host system is shown.

[0024] As shown in FIG. 1, the battery pack 1 may include one or more battery cells 11, a switching unit 14 connected in series to a first terminal side and / or a second terminal side of the battery cell 11 for controlling the flow of charge / discharge current of the battery cell 11, and a battery management system 20 that monitors the voltage, current, temperature, etc. of the battery pack 1 and manages it to prevent overcharging and overdischarging, etc.

[0025] In this case, the battery pack 1 may be provided with a plurality of battery cells 11, sensors 12, switching units 14, and battery management systems 20. For example, the first terminal may be the (+) terminal of the battery cell 11, and the second terminal may be the (-) terminal.

[0026] Here, the switching unit 14 is an element for controlling the flow of current for charging or discharging the multiple battery cells 11, and for example, at least one relay, electromagnetic contactor, etc. can be used depending on the specifications of the battery pack 1.

[0027] The plurality of battery cells 11 may include cylindrical batteries. A cylindrical battery refers to a battery in which battery materials are packaged in a cylindrical shape. When the plurality of battery cells 11 include cylindrical batteries, if lithium deposition occurs inside the cylindrical batteries during constant voltage charging of the battery cells 11, a phenomenon in which the current flowing through the battery cells 11 increases may occur. This phenomenon is caused by heat generation and an increase in leakage current due to lithium deposition inside the cylindrical batteries. This will be described later with reference to FIG. 3.

[0028] The battery management system 20 is an interface that receives input of measured values ​​of the various parameters described above, and may include a plurality of terminals and circuits connected to these terminals for processing the received input values. The battery management system 20 may also control the ON / OFF of a switching unit 14, such as a relay or contactor, and may be connected to the battery cells 11 to monitor the status of each battery cell 11.

[0029] The upper controller 2 can transmit a control signal for the battery cells 11 to the battery management system 20. As a result, the operation of the battery management system 20 can be controlled based on the signal applied from the upper controller 2.

[0030] According to an embodiment, the battery management system 20 may include the battery diagnostic device 100 of Fig. 2. According to another embodiment, the battery management system 20 may be a system different from the battery diagnostic device 100 of Fig. 2. That is, the battery diagnostic device 100 of Fig. 2 may be included in the battery pack 1, or may be configured as a separate device external to the battery pack 1. For convenience of explanation, the following description will be given on the assumption that the battery diagnostic device 100 is configured as a separate device external to the battery pack 1. Furthermore, the following operation of the battery diagnostic device 100 may be performed by a BMS (Battery Management System) in the vehicle, or may be performed by various devices such as a server, a cloud, a charger, or a charger / discharger.

[0031] Fig. 2 is a diagram illustrating a battery diagnostic device according to an embodiment disclosed herein. Fig. 3 is a graph of current over time for a battery cell generated by a battery diagnostic device according to an embodiment disclosed herein. Fig. 4 is a diagram illustrating current data for region A in Fig. 3 together with a moving average line for the current data. Fig. 5 is a diagram illustrating the difference between the current data and the moving average line in Fig. 4.

[0032] First, referring to FIG. 2, a battery diagnostic device 100 according to an embodiment disclosed in this specification may include a power supply unit 110, an information acquisition unit 120, a storage unit 130, and a controller 140.

[0033] The power supply unit 110 can charge the battery cell 11. The power supply unit 110 can charge the battery cell 11 by supplying a voltage and a current to the battery cell 11. According to the embodiment, the power supply unit 110 can supply a constant current to the battery cell 11 to increase the voltage of the battery cell 11. The battery cell 11 can be charged by receiving a current from the power supply unit 110. A section in which the battery cell 11 receives a constant current from the power supply unit 110 can be defined as a constant current charging section.

[0034] When the voltage of the battery cell 11 reaches a specific value, the power supply unit 110 may charge the battery cell 11 while maintaining the voltage of the battery cell 11 constant and gradually reducing the amount of current supplied to the battery cell 11. This allows the remaining capacity of the battery cell 11 that has not been charged during the constant current charging section to be charged. A section in which the battery cell 11 receives a constant voltage supply from the power supply unit 110 may be defined as a constant voltage charging section. The power supply unit 110 may be connected to the battery cell 11 to supply voltage and current to the battery cell 11.

[0035] The information acquiring unit 120 can acquire data of the battery cell 11. According to an embodiment, the information acquiring unit 120 can acquire voltage data, current data, and temperature data of the battery cell 11 over time. That is, the information acquiring unit 120 can measure the voltage across the battery cell 11, the current flowing into the battery cell 11, and the temperature of the battery cell 11. To this end, the information acquiring unit 120 can be connected to the battery cell 11.

[0036] Furthermore, the information acquisition unit 120 can transmit the voltage data, current data, and temperature data of the battery cell 11 to the storage unit 130 or the controller 140 .

[0037] The storage unit 130 can store the voltage data, current data, and temperature data of the battery cells 11 transmitted from the information acquisition unit 120. According to the embodiment, the storage unit 130 can transmit the voltage data, current data, and temperature data of the battery cells 11 to the controller 140.

[0038] The controller 140 can diagnose the state of the battery cell 11. That is, the controller 140 can determine the state of the battery cell 11 in the above-mentioned constant voltage charging section based on the current data transmitted from the information acquisition unit 120 or the storage unit 130. To this end, the controller 140 can generate a graph relating to the charging time and current of the battery cell 11 based on the current data, classify the current data, and analyze the generated graph.

[0039] 3, the controller 140 may generate a graph showing data of the battery cell 11 during the constant voltage charging period. That is, the controller 140 may generate a graph in which a first axis indicates time and a second axis indicates current, voltage, and temperature values ​​based on the data of the battery cell 11 during the constant voltage charging period. According to an embodiment, the first axis of the graph may be the x-axis and the second axis may be the y-axis. According to an embodiment, the origin of the graph may be the start point of the constant voltage charging period, and the end point of the first axis of the graph may be the end point of the constant voltage charging period.

[0040] In the constant voltage charging section, the power supply unit 110 maintains the voltage of the battery cell 11 constant, so that the voltage of the battery cell 11 can be shown as a constant value on the graph generated by the controller 140. That is, the voltage of the battery cell 11 can be maintained constant from the start of charging to the end of charging in the constant voltage charging section.

[0041] During the constant voltage charging period, the power supply unit 110 maintains the voltage of the battery cell 11 constant and gradually reduces the current supplied to the battery cell 11, so that the graph generated by the controller 140 shows a general tendency for the current of the battery cell 11 to decrease.

[0042] According to the embodiment, if lithium deposition occurs inside the battery cell 11 during the constant voltage charging period, the temperature of the battery cell 11 may rise rapidly. This phenomenon is caused by energy conversion in which electric energy is converted into thermal energy when a current is supplied to the lithium deposited inside the battery cell 11. Furthermore, the current supplied to the lithium may increase the current flowing into the battery cell 11 during the constant voltage charging period. This phenomenon may cause a malfunction of the battery cell 11, and a battery cell 11 exhibiting this phenomenon may be an abnormal battery. In other words, if the current flowing into the battery cell 11 increases during the constant voltage charging period, it may be a defective battery in which lithium has been deposited inside the battery cell 11. Therefore, the controller 140 can diagnose the state of the battery cell 11 based on the current data of the battery cell 11.

[0043] However, because the current data of the battery cell 11 may contain various noises, such as noise from current measurement or noise from the charger / discharger itself, it is necessary to remove the influence of the noise contained in the current data in order to accurately diagnose the battery cell 11. That is, during a constant voltage charging period of a normal battery cell 11, the current supplied to the battery cell 11 generally gradually decreases, but due to the influence of noise, the current may be measured as increasing in some periods, and therefore it is necessary to remove the influence of the noise. To this end, the controller 140 needs to appropriately set the time interval between two points in time for comparing the current data. To set the time interval between two points in time, the controller 140 may classify the current data of the battery cell 11 into a DC component and an AC component and set the time interval between two points in time based on the AC component.

[0044] 4, the controller 140 may generate a moving average line 203 of the current data based on the current data of the battery cell 11. Here, the moving average line 203 may be defined as a line formed by sequentially connecting values ​​obtained by arithmetically averaging the current data of the battery cell 11 over a certain period of time. The controller 140 may define the moving average line 203 of the current data as a DC component of the current data.

[0045] 5, the controller 140 may classify the current data into a DC component and an AC component using the moving average line 203. According to an embodiment, the controller 140 may extract the AC component of the current data based on the difference between the current data and the moving average line 203 of the current data. That is, the controller 140 may calculate the difference between the current value included in the current data for each charging time and the value indicated by the moving average line 203 of the current data, and extract the AC component of the current data corresponding to each time by combining the calculated values. In other words, the controller 140 may define the difference between the current data and the moving average line 203 of the current data as the AC component of the current data. According to an embodiment, since the difference between the current data and the moving average line 203 of the current data corresponds to the AC component, the central value of the AC component may be zero.

[0046] The controller 140 can calculate the standard deviation of the AC component of the current data. Here, the standard deviation can be defined as a value that shows a scatter plot based on the difference between the AC component at each time point of the current data and the average of the AC components. In other words, the standard deviation can be defined as the square root of the sum of the squares of the differences between the AC component at each time point and the average of the AC components, divided by the number of time points.

[0047] In an ideal constant voltage charging period of the battery cell 11, the power supply unit 110 applies a constant DC voltage to the battery cell 11, so the frequency of the power applied from the power supply unit 110 to the battery cell 11 may be 0. Since the frequency is 0, the impedance of the battery cell 11 has a constant value, and therefore the current of the battery cell 11 can have only a DC component.

[0048] Therefore, the AC component of the current data of the battery cell 11 can be defined as an influence of noise. According to the embodiment, the noise in the current data of the battery cell 11 can include noise in the current measurement and noise of the charger / discharger itself.

[0049] Due to noise in the current data, the current data of the battery cell 11 may be measured as increasing in some sections during the constant voltage charging section. Therefore, when the noise is large, it is necessary to select two points in time separated by an interval sufficient to ignore the noise and compare the current values ​​at the two points in time. That is, when the noise is large, the interval between the two points in time for comparing the current data may be set larger than the interval when the noise is small.

[0050] To this end, the controller 140 can match the standard deviation of the AC component of the current data with the interval between two points in time for comparing the current data. According to an embodiment, the controller 140 can set the standard deviation of the AC component to be proportional to the interval between two points in time and generate a lookup table that matches them one-to-one. That is, the controller 140 can preset a lookup table that matches the standard deviation of the AC component with the interval between two points in time, calculate the standard deviation of the AC component of the battery cell 11, and obtain the corresponding interval between two points in time in the lookup table.

[0051] Referring again to FIG. 3, the controller 140 can diagnose the state of the battery cell 11 based on a graph generated regarding data of the battery cell 11 during the constant voltage charging period. The controller 140 can set a first time point defined on the time axis of the graph and a second time point that is a time point at which a predetermined time has elapsed since the first time point. According to an embodiment, the controller 140 can set the first time point as the origin and the second time point as a time point that is the interval between the two time points acquired in FIG. 5 from the first time point. The interval between the first time point and the second time point on the graph is the interval acquired in FIG. 5, and the interval between the first time point and the second time point can be defined as d.

[0052] A point on the graph current line 200 corresponding to a first time point can be defined as a first point 201. A point on the graph current line 200 corresponding to a second time point can be defined as a second point 202. A point on the graph temperature line 300 corresponding to a first time point can be defined as a third point 301. A point on the graph temperature line 300 corresponding to a second time point can be defined as a fourth point 302.

[0053] The controller 140 can compare the current value at the first point 201 with the current value at the second point 202. Because the power supply unit 110 maintains the voltage of the battery cell 11 at a constant voltage and gradually reduces the current supplied to the battery cell 11 over time, the current value at the second point 202 can be smaller than the current value at the first point 201. In this way, if the current value at the second point 202 is smaller than the current value at the first point 201, the temperature of the battery can decrease. That is, the temperature value at the fourth point 302 can be smaller than the temperature value at the third point 301.

[0054] If the controller 140 determines that the current value at the second point 202 is smaller than the current value at the first point 201, the controller 140 may determine whether the second time point is the end point of the constant voltage charging section. That is, the controller 140 may determine whether the second time point is the end point of the constant voltage charging section. In this case, if the controller 140 determines that the second time point is the end point of the constant voltage charging section, the controller 140 may complete the diagnosis of the battery cell 11. If the controller 140 determines that the second time point is not the end point of the constant voltage charging section, the controller 140 may change the first time point and the second time point while maintaining the interval between the first time point and the second time point. According to an embodiment, the controller 140 may change the first time point and the second time point to a time point obtained by adding a preset time to each of the first time point and the second time point.

[0055] As the controller 140 changes the first and second points in time, the first point 201 corresponding to the first point in the current line 200, the second point 202 corresponding to the second point in the current line 200, the third point 301 corresponding to the first point in the temperature line 300, and the fourth point 302 corresponding to the second point in the temperature line 300 may all be changed.

[0056] The controller 140 can compare the current value at the first point 201, which is newly defined by changing the first time point and the second time point, with the current value at the second point 202. According to an embodiment, the controller 140 can determine that the corresponding battery cell 11 is abnormal if the current value at the second point 202 is greater than the current value at the first point 201. That is, the current value at the second point 202 being greater than the current value at the first point 201 means that there is a section in which the current value increases over time in the constant voltage charging section, and the controller 140 can determine that the corresponding battery cell 11 is abnormal. In this case, lithium deposition occurs inside the battery cell 11, current is supplied to the deposited lithium, and the electrical energy is converted into thermal energy, causing the battery cell 11 to generate heat. Therefore, the temperature value at the fourth point 302 can be higher than the temperature value at the third point 301.

[0057] The controller 140 can compare the current value at the first point 201 with the current value at the second point 202 and repeat the operation of changing the first time point and the second time point. In this way, the controller 140 can analyze the current state throughout the constant voltage charging section of the battery cell 11 and determine whether the current is increasing due to lithium deposition inside the battery cell 11.

[0058] Therefore, the battery diagnostic device 100 including the controller 140 can diagnose the state of the battery cell 11 by analyzing the current data in the constant voltage charging section. If the diagnosis determines that the battery cell 11 is abnormal, the controller 140 can provide information about the abnormal battery cell to the user. For example, the controller 140 can provide information about the abnormal battery cell to a user terminal via a communication unit (not shown), and can also provide information about the abnormal battery cell via a display provided in the vehicle, a charger, or the like.

[0059] As a result, by the battery diagnostic device 100 analyzing the current data of the battery cells 11, it is possible to inspect abnormal battery cells 11 early and replace the battery cells 11, thereby preventing fires caused by heat generation from the battery cells 11.

[0060] FIG. 6 is a flowchart illustrating a battery diagnostic method according to one embodiment disclosed herein. The embodiment shown in FIG. 6 is just one embodiment, and the order of operations according to various embodiments of the present invention may differ from that shown in FIG. 6, and some steps shown in FIG. 6 may be omitted, the order between steps may be changed, or steps may be merged.

[0061] Referring to FIG. 6, the battery diagnosis method may include an operation of acquiring current data of a battery cell (S110), an operation of extracting an AC component from the current data (S120), an operation of setting a first time point and a second time point using a time interval acquired based on the AC component (S130), and an operation of determining the state of the battery cell based on the current values ​​at the first and second time points (S140).

[0062] Hereinafter, the operations S110 to S140 will be specifically described with reference to FIGS. In operation S110, the battery diagnostic device 100 can acquire current data of the battery cell 11.

[0063] According to the embodiment, the battery diagnostic device 100 can acquire not only current data of the battery cell 11 but also voltage data and temperature data of the battery cell 11 over time. That is, the battery diagnostic device 100 can measure the voltage across the battery cell 11, the current flowing into the battery cell 11, and the temperature of the battery cell 11. For this purpose, the battery diagnostic device 100 can be connected to the battery cell 11.

[0064] The battery diagnostic device 100 can generate a graph showing data of the battery cell 11 in the constant voltage charging section. That is, the battery diagnostic device 100 can generate a graph in which a first axis indicates time and a second axis indicates current, voltage, and temperature values ​​based on the data of the battery cell 11 in the constant voltage charging section. According to an embodiment, the first axis of the graph may be the x-axis and the second axis may be the y-axis. According to an embodiment, the origin of the graph may be the start point of the constant voltage charging section, and the end point of the first axis of the graph may be the end point of the constant voltage charging section. After operation S110, operation S120 can be performed.

[0065] In operation S120, the battery diagnostic device 100 can extract the AC component from the current data. To this end, the battery diagnostic device 100 can generate a moving average line 203 of the current data based on the current data of the battery cell 11. The battery diagnostic device 100 can define the moving average line 203 of the current data as the DC component of the current data. That is, the battery diagnostic device 100 can use the moving average line 203 to classify the current data into a DC component and an AC component.

[0066] The battery diagnostic device 100 can extract the AC component of the current data based on the difference between the current data and the moving average line 203 of the current data. That is, the battery diagnostic device 100 calculates the difference between the current value included in the current data for each charging time and the value indicated by the moving average line 203 of the current data, and connects these differences to extract the AC component of the current data corresponding to each time. In other words, the battery diagnostic device 100 can define the difference between the DC data and the moving average line 203 of the DC data as the AC component of the current data. According to the embodiment, since the difference between the current data and the moving average line 203 of the current data corresponds to the AC component, the center value of the AC component may be zero. After operation S120, operation S130 can be performed.

[0067] In operation S130, the battery diagnostic device 100 can set the first time point and the second time point using the time interval obtained based on the AC component. The battery diagnostic device 100 can calculate the standard deviation of the AC component of the current data. In an ideal constant voltage charging period of the battery cell 11, the power supply unit 110 applies a constant DC voltage to the battery cell 11, so the frequency of the power supply unit 110 may be 0. Since the frequency is 0, the impedance of the battery cell 11 has a constant value, and therefore the current of the battery cell 11 can have only a DC component.

[0068] Therefore, the AC component of the current data of the battery cell 11 may be affected by noise. According to the embodiment, the noise in the current data of the battery cell 11 may include noise in the current measurement and noise in the charger / discharger itself.

[0069] Due to noise in the current data, the current data of the battery cell 11 may be measured as increasing in some sections during the constant voltage charging section. Therefore, when the noise is large, two points in time should be selected with an interval large enough to ignore the noise, and the current values ​​at the two points in time should be compared. In other words, when the noise is large, the interval between the two points in time for comparing the current data should be larger than when the noise is small.

[0070] To this end, the battery diagnostic device 100 can match the standard deviation of the AC component of the current data with the interval between two points in time for comparing the current data. According to an embodiment, the battery diagnostic device 100 can set the standard deviation of the AC component to be proportional to the interval between two points in time and generate a lookup table that matches them one-to-one. That is, the battery diagnostic device 100 can preset a lookup table that matches the standard deviation of the AC component with the interval between two points in time, calculate the standard deviation of the AC component of the battery cell 11, and obtain the corresponding interval between two points in time on the lookup table. After operation S130, operation S140 can be performed.

[0071] In operation S110, the battery diagnostic device 100 can determine the state of the battery cell 11 based on the current values ​​at the first and second points in time. The battery diagnostic device 100 can determine the state of the battery cell 11 by comparing the current value corresponding to the first point in time with the current value corresponding to the second point in time, as will be described in detail below with reference to FIG.

[0072] FIG. 7 is a flowchart specifically showing the operation of determining the state of the battery cell 11 based on the current values ​​at the first and second points in time in FIG. Referring to FIG. 7, the operation of determining the state of the battery cell based on the current values ​​at the first and second points in time includes an operation of determining whether the current value at the second point in time is greater than the current value at the first point in time (S141), an operation of determining whether the second point in time is the charging completion point in time (S142), an operation of changing the first and second points in time (S143), an operation of determining that the battery cell is normal (S144), and an operation of determining that the battery cell is abnormal (S145).

[0073] In operation S141, the battery diagnostic device 100 can set a first time point defined on the time axis of the graph and a second time point that is a time point at which a predetermined time has elapsed since the first time point. According to an embodiment, the battery diagnostic device 100 can set the first time point as the origin and set the second time point as a time point at which the interval between the two time points obtained in FIG. 5 has elapsed since the first time point.

[0074] A point on the graph corresponding to a first time point in the current line 200 can be defined as a first point 201. A point on the graph corresponding to a second time point in the current line 200 can be defined as a second point 202.

[0075] The battery diagnostic device 100 can compare the current value at the first point 201 with the current value at the second point 202. Here, the battery diagnostic device 100 can determine which of the current values ​​at the first point 201 and the second point 202 is larger. If the battery diagnostic device 100 determines that the current value at the second point in time is larger than the current value at the first point in time, it can perform operation S145. If the battery diagnostic device 100 determines that the current value at the second point in time is smaller than the current value at the first point in time, it can perform operation S142.

[0076] In operation S142, the battery diagnostic device 100 can determine whether the second time point is the charging completion time point. That is, when the battery diagnostic device 100 determines that the current value at the second point 202 is smaller than the current value at the first point 201, it can determine whether the second time point is the end point of the constant voltage charging section.

[0077] If the battery diagnostic device 100 determines that the second time point is the charging completion time point, it can perform operation S114. If the battery diagnostic device 100 determines that the second time point is not the charging completion time point, it can perform operation S143.

[0078] In operation S143, the battery diagnostic device 100 can change the first time point and the second time point. That is, the battery diagnostic device 100 can change the first time point and the second time point by adding a previously set time to each of the first time point and the second time point while maintaining the interval between the first time point and the second time point. After operation S143, operation S141 can be performed.

[0079] In operation S144, the battery diagnostic device 100 can determine that the battery cell 11 being diagnosed is normal. When the battery diagnostic device 100 changes the first and second time points and diagnoses the battery cell 11 from the time of constant voltage charging to the end point of charging, and the current value of the battery cell 11 corresponding to the first time point is greater than the current value of the battery cell 11 corresponding to the second time point, the battery diagnostic device 100 can determine that the battery cell 11 is normal.

[0080] In operation S145, the battery diagnostic device 100 can determine that the battery cell 11 being diagnosed is abnormal. That is, when the battery diagnostic device 100 determines that the current value at the second time point is greater than the current value at the first time point, it can determine that the battery cell 11 is abnormal.

[0081] In other words, the current value at the second point 202 being greater than the current value at the first point 201 means that there is a section in which the current value increases over time in the constant voltage charging section, and the battery diagnostic device 100 can determine that the battery cell 11 is abnormal. In this case, lithium deposition occurs inside the battery cell 11, current is supplied to the deposited lithium, and the electrical energy is converted into thermal energy, causing the battery cell 11 to generate heat. This can cause the temperature of the battery cell 11 to rise rapidly.

[0082] FIG. 8 illustrates a computing system for implementing a battery diagnostic method according to one embodiment of the present disclosure. Referring to FIG. 8, a computing system 400 according to one embodiment disclosed herein may include an MCU 410, a memory 420, an input / output I / F 430, and a communication I / F 440.

[0083] The MCU 410 may be a processor that executes various programs (e.g., an SOH calculation program, a cell balancing execution target determination program, etc.) stored in the memory 420, processes various data including the SOC, SOH, etc. of multiple battery cells through such programs, and performs the functions of the battery diagnostic device 100 described above with reference to Figures 1 to 7. The MCU 410 may be, but is not limited to, a BMS, another PC, or a cloud.

[0084] The memory 420 can store various programs related to calculating the SOH of the battery cells and determining whether cell balancing is to be performed. The memory 420 can also store various data such as SOC and SOH data for each battery cell.

[0085] A plurality of such memories 420 may be provided as necessary. The memories 420 may be volatile memories or nonvolatile memories. As the volatile memories 420, RAM, DRAM, SRAM, etc. may be used. As the nonvolatile memories 420, ROM, PROM, EAROM, EPROM, EEPROM, flash memory, etc. may be used. The examples of the memories 420 listed above are merely illustrative and are not limited to these examples.

[0086] The input / output I / F 430 can provide an interface that connects input devices (not shown) such as a keyboard, mouse, or touch panel, and output devices such as a display (not shown), to the MCU 410, enabling data to be sent and received.

[0087] The communication I / F 440 is configured to be able to send and receive various data to and from a server, and may be any device that supports wired or wireless communication. For example, programs and various data for calculating the SOH of battery cells and determining which cells are to be balanced can be sent and received from a separately provided external server via the communication I / F 440. Thus, a battery management method according to one embodiment disclosed herein may be stored in memory 420 and executed by MCU 410.

[0088] The above description is merely an illustrative example of the technical ideas disclosed in this specification, and a person having ordinary skill in the art to which the embodiments disclosed in this specification belong may make various modifications and variations within the scope that does not deviate from the essential characteristics of the embodiments disclosed in this specification.

[0089] Therefore, the embodiments disclosed in this specification are intended to illustrate, not limit, the technical ideas disclosed in this specification, and such embodiments do not limit the scope of the technical ideas disclosed in this specification. The scope of protection of the technical ideas disclosed in this specification should be interpreted according to the claims below, and all technical ideas within the equivalent range should be interpreted as being included in the scope of rights of this specification.

Claims

1. an information acquisition unit that acquires current data of the battery cell; a controller that acquires the current data during a constant voltage charging interval of the battery cell, sets a first point in time at which the current data is acquired and a second point in time at which the current data is acquired after a predetermined time has elapsed from the first point in time, and determines a state of the battery cell based on the current values ​​at the first point in time and the second point in time; A battery diagnostic device comprising:

2. The battery diagnostic device according to claim 1 , wherein the controller further determines the battery cell to be an abnormal battery cell when the current value at the second point in time is greater than the current value at the first point in time.

3. 3. The battery diagnostic device of claim 2, wherein the controller further changes the first and second points in time while maintaining a time interval between the first and second points in time, and compares the current value at the first point in time with the current value at the second point in time.

4. The battery diagnostic device according to claim 2 , wherein the abnormal battery cell includes a battery cell in which lithium (Li) is precipitated.

5. 2. The battery diagnostic device according to claim 1, wherein the controller further classifies the current data into a DC component and an AC component using a moving average of the current data.

6. The battery diagnostic device according to claim 5 , wherein the controller further removes the DC component from the current data to extract the AC component.

7. The controller further calculates a standard deviation of the AC component; The battery diagnostic device according to claim 6 , wherein a time interval between the first time point and the second time point is set based on the standard deviation.

8. The battery diagnostic device according to claim 1 , further comprising a storage unit for storing current data of the battery cells measured by the information acquisition unit.

9. acquiring current data of the battery cell during a constant voltage charging period of the battery cell; setting a first time point and a second time point that is a time point at which a predetermined time has elapsed since the first time point, using a time interval acquired based on the AC component of the current data; determining a state of the battery cell based on current values ​​at the first time point and the second time point; A battery diagnostic method comprising:

10. 10. The battery diagnostic method according to claim 9, wherein the step of determining the state of the battery cell includes the step of determining that the battery cell is an abnormal battery cell if the current value at the second point in time is greater than the current value at the first point in time.

11. The battery diagnostic method according to claim 10 , wherein the abnormal battery cell includes a battery cell in which lithium (Li) is precipitated inside the battery cell.

12. 10. The battery diagnostic method of claim 9, wherein the step of determining the state of the battery cell includes the steps of: generating a graph based on the current data, the graph having a first axis representing time and a second axis representing a current value; changing the first time point and the second time point while maintaining a time interval between the first time point and the second time point defined in the graph; and comparing the current value at the first time point with the current value at the second time point.

13. 10. The battery diagnostic method according to claim 9, wherein the step of setting the time interval includes the step of dividing the current data into a DC component and an AC component using a moving average of the current data.

14. The battery diagnostic method according to claim 13 , wherein the step of setting the time interval includes the step of removing the DC component from the current data and extracting the AC component after the step of dividing the current data.

15. 15. The battery diagnostic method according to claim 14, wherein the step of setting the time interval includes the step of calculating a standard deviation of the AC component after the step of extracting the AC component, and setting the time interval between the first time point and the second time point based on the standard deviation.

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