Battery inspection apparatus and battery inspection method

Abstract

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

Description

Technology Field

[0001] The embodiments disclosed in this document relate to a battery diagnostic device and a battery diagnostic method. Background Technology

[0002] Recently, as portable devices such as smartphones and laptop computers, means of transportation such as electric vehicles, electric scooters, and electric two-wheeled vehicles, and devices for stably supplying and managing power such as Energy Storage Systems (ESS) are widely used, interest in batteries is increasing and development is becoming more active.

[0003] A battery is a component for supplying power to devices or systems. In this case, the battery may be used in a form where a single secondary battery supplies power as a battery cell alone, or multiple secondary batteries may be used to supply power by forming a single battery module or a single battery bank.

[0004] Meanwhile, batteries can malfunction due to various causes. For example, lithium (Li) ions may precipitate inside the battery, and as current is supplied to the precipitated lithium, the battery may generate heat.

[0005] Meanwhile, batteries may fail due to various causes. 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. Regarding the diagnosis of lithium precipitation, there are prior art documents concerning "device and method for diagnosing battery degradation" (KR 10-2261481 B1) and "method and device for determining the precipitation of lithium dendrites" (JP 2013-089363 A). The problem to be solved

[0006] One objective of the embodiments disclosed in this document is to provide a battery diagnostic device and a battery diagnostic method for diagnosing a battery.

[0007] The technical problems of the embodiments described in this document are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by a person skilled in the art to which the present invention pertains from the description below. means of solving the problem

[0008] A battery diagnostic device according to one embodiment disclosed in this document includes an information acquisition unit that acquires current data including a current value over time in a constant voltage charging section of a battery cell, a controller that sets a first time point at which the current data is acquired and a second time point at which the current data is acquired after a predetermined time has elapsed from the first time point, and determines the state of the battery cell based on whether the current value at the first time point exceeds the current value at the second time point.

[0009] 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 exceeds the current value at the first time point.

[0010] According to one embodiment, the controller can change the first time point and the second time point while maintaining a time interval between the first time point and the second time point, and compare the current value of the first time point with the current value of the second time point.

[0011] According to one embodiment, the abnormal battery cell may include a battery cell in which lithium (Li) is precipitated inside the battery cell.

[0012] According to one embodiment, the controller can separate the current data into a DC component and an AC component using the moving average of the current data.

[0013] According to one embodiment, the controller can extract the alternating current component by removing the direct current component from the current data.

[0014] According to one embodiment, the controller can calculate the standard deviation of the alternating current component and set the time interval between the first time point and the second time point based on the standard deviation.

[0015] According to one 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.

[0016] A battery diagnostic method according to one embodiment disclosed in this document includes the steps of: acquiring current data including a current value over time in a constant voltage charging section of a battery cell; setting a first time point and a second time point which is a time point after a predetermined time has elapsed from the first time point using a time interval acquired based on the alternating current component of the current data; and determining the state of the battery cell based on whether the current value at the first time point exceeds the current value at the second time point.

[0017] 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 exceeds the current value at the first time point.

[0018] According to one embodiment, the abnormal battery cell may include a battery cell in which lithium (Li) is precipitated inside the battery cell.

[0019] According to one embodiment, the step of determining the state of the battery cell may include generating a graph in which the first axis is time and the second axis is current value based on the current data, changing the first time point and the second time point while maintaining the 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.

[0020] According to one embodiment, the step of setting the time interval may include the step of separating the current data into a DC component and an AC component using the moving average of the current data.

[0021] According to one embodiment, the step of setting the time interval may include the step of extracting the alternating current component by removing the direct current component from the current data after the distinguishing step.

[0022] According to one embodiment, the step of setting the time interval may include calculating the standard deviation of the alternating current component after the step of extracting the alternating current component, and setting the time interval between the first time point and the second time point based on the standard deviation.

[0023] Specific details of other embodiments are included in the detailed description and drawings. Effects of the invention

[0024] According to the battery diagnostic device and battery diagnostic method according to the embodiments disclosed in this document, the state of the battery can be diagnosed based on the current data of the battery.

[0025] According to the battery diagnostic device and battery diagnostic method according to the embodiments disclosed in this document, by diagnosing lithium precipitation inside the battery, it is possible to detect an abnormal battery early and prevent overheating and fire of the battery in advance. Brief explanation of the drawing

[0026] FIG. 1 is a block diagram showing a battery pack according to one embodiment disclosed in this document. FIG. 2 is a drawing showing a battery diagnostic device according to one embodiment disclosed in this document. FIG. 3 is a graph of current over time of a battery cell generated by a battery diagnostic device according to one embodiment disclosed in this document. Figure 4 is a diagram showing the current data of area A of Figure 3 and the moving average line of the current data together. Figure 5 is a diagram showing the difference between the current data and the moving average line of Figure 4. FIG. 6 is a flowchart showing a battery diagnostic method according to one embodiment disclosed in this document. FIG. 7 is a flowchart specifically showing the operation of determining the state of a battery cell based on the current values ​​at the first and second time points of FIG. 6. FIG. 8 shows a computing system that executes a battery diagnostic method according to one embodiment disclosed in this document. Specific details for implementing the invention

[0027] The embodiments disclosed in this document are described in detail below with reference to exemplary drawings. It should be noted that in assigning reference numerals to the components of each drawing, the same components are given the same reference numeral whenever possible, even if they are shown in different drawings. Furthermore, in describing the embodiments disclosed in this document, detailed descriptions of related known configurations or functions are omitted if it is determined that such detailed descriptions would hinder understanding of the embodiments disclosed in this document.

[0028] In describing the components of the embodiments disclosed in this document, terms such as "first," "second," etc., may be used. These terms are intended merely to distinguish the components from other components and do not limit the essence, order, or sequence of the components. Furthermore, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the embodiments disclosed in this document pertain. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0029] FIG. 1 is a block diagram showing a battery pack according to one embodiment disclosed in this document.

[0030] Referring to FIG. 1, a battery control system including a battery pack (1) and a higher controller (2) included in a higher system according to one embodiment disclosed in this document is schematically shown.

[0031] As illustrated in FIG. 1, the battery pack (1) may include one or more battery cells (11), a switching unit (14) connected in series to the first terminal side and / or the second terminal side of the battery cell (11) to control the flow of charging and discharging current of the battery cell (11), and a battery management system (20) that monitors the voltage, current, temperature, etc. of the battery pack (1) to prevent overcharging and over-discharging.

[0032] In this case, the battery pack (1) may be equipped 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.

[0033] Here, the switching unit (14) is a device for controlling the current flow for charging or discharging a plurality of battery cells (11), and, for example, depending on the specifications of the battery pack (1), at least one relay, magnetic contactor, etc. may be used.

[0034] A plurality of battery cells (11) may include cylindrical batteries. A cylindrical battery refers to a battery in which the battery material is packaged into a cylinder. Since a plurality of battery cells (11) include cylindrical batteries, if lithium precipitation occurs inside the cylindrical battery during constant voltage charging of the battery cells (11), a phenomenon may occur in which the current flowing through the battery cells (11) increases. This phenomenon may be attributed to heat generation and an increase in leakage current caused by lithium precipitation inside the cylindrical battery. This will be described later in FIG. 3.

[0035] The battery management system (20) is an interface that receives values ​​of various parameters measured above, and may include a plurality of terminals and a circuit connected to these terminals to perform processing of the received values. Additionally, the battery management system (20) may control the ON / OFF of a switching unit (14), such as a relay or contactor, and may be connected to a battery cell (11) to monitor the status of each battery cell (11).

[0036] The upper controller (2) can transmit a control signal for the battery cell (11) to the battery management system (20). Accordingly, the operation of the battery management system (20) can be controlled based on the signal applied from the upper controller (2).

[0037] 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 different system 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 another device outside the battery pack (1). For convenience of explanation, the following description assumes that the battery diagnostic device (100) is configured as another device outside the battery pack (1). Furthermore, the operation of the battery diagnostic device (100) below may be performed by a Battery Management System (BMS) within the vehicle, as well as by various devices such as a server, cloud, charger, or charger / discharger.

[0038] FIG. 2 is a drawing showing a battery diagnostic device according to an embodiment disclosed in this document. FIG. 3 is a graph of current over time of a battery cell generated by a battery diagnostic device according to an embodiment disclosed in this document. FIG. 4 is a drawing showing the current data in area A of FIG. 3 and the moving average line of the current data together. FIG. 5 is a drawing showing the difference between the current data and the moving average line of FIG. 4.

[0039] First, referring to FIG. 2, a battery diagnostic device (100) according to one embodiment disclosed in this document may include a power supply unit (110), an information acquisition unit (120), a storage unit (130), and a controller (140).

[0040] The power supply unit (110) can charge the battery cell (11). The power supply unit (110) can charge the battery cell (11) by supplying voltage and current to the battery cell (11). According to an embodiment, the power supply unit (110) can supply a constant current to the battery cell (11) and increase the voltage of the battery cell (11). The battery cell (11) can be charged by receiving current from the power supply unit (110). The period during which the battery cell (11) receives a constant current from the power supply unit (110) can be defined as a constant current charging period.

[0041] When the voltage of the battery cell (11) reaches a specific value, the power supply unit (110) can charge the battery cell (11) by maintaining the voltage of the battery cell (11) constant and gradually reducing the amount of current supplied to the battery cell (11). Through this, the remaining capacity of the battery cell (11) that was not charged during the constant current charging period can be charged. The period during which the battery cell (11) receives a constant voltage from the power supply unit (110) can be defined as the constant voltage charging period. The power supply unit (110) can be connected to the battery cell (11) to supply voltage and current to the battery cell (11).

[0042] The information acquisition unit (120) can acquire data of the battery cell (11). According to an embodiment, the information acquisition unit (120) can acquire voltage data, current data, and temperature data of the battery cell (11) over time. That is, the information acquisition unit (120) can measure the voltage at both ends of the battery cell (11), the current flowing into the battery cell (11), and the temperature of the battery cell (11). To do this, the information acquisition unit (120) can be connected to the battery cell (11).

[0043] Additionally, the information acquisition unit (120) can transmit voltage data, current data, and temperature data of the battery cell (11) to the storage unit (130) or controller (140).

[0044] The storage unit (130) can receive and store voltage data, current data, and temperature data of the battery cell (11) from the information acquisition unit (120). According to an embodiment, the storage unit (130) can transmit the voltage data, current data, and temperature data of the battery cell (11) to the controller (140).

[0045] 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 aforementioned constant voltage charging section based on current data received from the information acquisition unit (120) or the storage unit (130). To this end, the controller (140) can generate a graph regarding the charging time and current of the battery cell (11) based on the current data, classify the current data, and analyze the generated graph.

[0046] Referring to FIG. 3, the controller (140) can generate a graph representing data of the battery cell (11) during a constant voltage charging period. That is, the controller (140) can generate a graph in which the first axis represents time and the second axis represents current, voltage, and temperature values ​​based on the data of the battery cell (11) during a 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 starting 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.

[0047] In the constant voltage charging section, the power supply unit (110) maintains the voltage of the battery cell (11) constant, so the voltage of the battery cell (11) can show 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 in the constant voltage charging section to the end of charging.

[0048] In the constant voltage charging section, 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 the current of the battery cell (11) may generally show a decreasing trend on the graph generated by the controller (140).

[0049] According to the embodiment, during the constant voltage charging section, if lithium deposition occurs inside the battery cell (11), the temperature of the battery cell (11) may rise rapidly. This phenomenon may be attributed to energy conversion in which electrical energy is converted into thermal energy as current is supplied to the lithium deposited inside the battery cell (11). Additionally, as current is supplied to the lithium, the current flowing into the battery cell (11) during the constant voltage charging section may increase. Such a phenomenon causes defects in the battery cell (11), and a battery cell (11) exhibiting such a phenomenon may be an abnormal battery. That is, if the current flowing into the battery cell (11) increases during the constant voltage charging section, it may be a defective battery in which lithium has been deposited inside the battery cell (11). Therefore, the controller (140) can diagnose the condition of the battery cell (11) based on the current data of the battery cell (11).

[0050] However, the current data of the battery cell (11) may contain various noises, such as noise from the current measurement or noise from the charger / discharger itself, so it may be necessary to remove the influence of the noise included in the current data for accurate diagnosis of the battery cell (11). That is, in the constant voltage charging section of a normal battery cell (11), the current supplied to the battery cell (11) generally decreases gradually, but there is a concern that the current may be measured as increasing in some sections due to the influence of noise, so it may be 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) can separate the current data of the battery cell (11) into a DC component and an AC component, and set the time interval between the two points in time based on the AC component.

[0051] Referring to FIG. 4, the controller (140) can generate a moving average line (203) of current data based on current data of the battery cell (11). Here, the moving average line (203) can be defined as a line formed by sequentially connecting the values ​​of the arithmetic average of the current data of the battery cell (11) over a certain period of time. The controller (140) can define the moving average line (203) of current data as the DC component of the current data.

[0052] Referring to FIG. 5, the controller (140) can utilize a moving average line (203) to separate current data into a direct current component and an alternating current component. According to an embodiment, the controller (140) can extract the alternating current 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) can calculate the difference between the current value contained in the current data and the value represented by the moving average line (203) of the current data for each charging time, and connect them to extract the alternating current component of the current data corresponding to each time. In other words, the controller (140) can define the difference between the current data and the moving average line (203) of the current data as the alternating current 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 alternating current component, the center value of the alternating current component may be 0.

[0053] The controller (140) can calculate the standard deviation of the alternating current component of the current data. Here, the standard deviation can be defined as a value representing the dispersion based on the difference between the alternating current component at each point in time and the average of the alternating current component. That is, the standard deviation can be defined as the square root of the value obtained by squaring the difference between the alternating current component at each point in time and the average of the alternating current component, adding them all together, and dividing by the number of points in time.

[0054] In the constant voltage charging section of an ideal 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) can be 0. Since the frequency is 0, the impedance of the battery cell (11) has a constant value, and accordingly, the current of the battery cell (11) can have only a DC component.

[0055] Accordingly, the alternating current component of the current data of the battery cell (11) can be defined as an influence of noise. According to an embodiment, the noise in the current data of the battery cell (11) may include noise in the current measurement and noise of the charger / discharger itself.

[0056] Due to noise in the current data, the current data of the battery cells (11) in the constant voltage charging section may be measured as increasing in some sections. Therefore, if the noise is large, it is necessary to select two points in time with an interval large enough to ignore the noise and compare the current values ​​at the two points in time. That is, the interval between the two points in time for comparing current data when the noise is large can be set to be larger than the interval when the noise is small.

[0057] To this end, the controller (140) can match the standard deviation of the alternating current component of the current data with the interval between two points in time for comparison of the current data. According to an embodiment, the controller (140) can set the standard deviation of the alternating current component to be proportional to the interval between two points in time and generate a lookup table that corresponds to it one-to-one. That is, the controller (140) can set up a lookup table that matches the standard deviation of the alternating current component with the interval between two points in time, calculate the standard deviation of the alternating current component of the battery cell (11), and obtain the interval between two points in time corresponding to it on the lookup table.

[0058] Referring again to FIG. 3, the controller (140) can diagnose the state of the battery cell (11) based on a graph generated regarding the data of the battery cell (11) during a constant voltage charging section. The controller (140) can set a first point in time defined on the time axis of the graph and a second point in time, which is a point in time after a predetermined amount of time has elapsed from the first point in time. According to an embodiment, the controller (140) can set the first point in time as the origin and set the second point in time as a point in time after the interval between the two points in time obtained in FIG. 5 from the first point in time. The interval between the first point in time and the second point in time on the graph is the interval obtained in FIG. 5, and the interval between the first point in time and the second point in time can be defined as d.

[0059] The point corresponding to the first time point among the current line (200) of the graph can be defined as the first point (201). The point corresponding to the second time point among the current line (200) of the graph can be defined as the second point (202). The point corresponding to the first time point among the temperature line (300) of the graph can be defined as the third point (301). The point corresponding to the second time point among the current line (200) of the graph can be defined as the fourth point (302).

[0060] The controller (140) can compare the current value at the first point (201) with the current value at the second point (202). Since 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) as time passes, the current value at the second point (202) may be smaller than the current value at the first point (201). In this way, when the current value at the second point (202) is smaller than the current value at the first point (201), the temperature of the battery may decrease. That is, the temperature value at the fourth point (302) may be smaller than the temperature value at the third point (301).

[0061] 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), it can determine whether the second point is the end point of the constant voltage charging section. That is, the controller (140) can determine whether the second point is the end point of charging. At this time, if the controller (140) determines that the second point is the end point of the constant voltage charging section, it can complete the diagnosis of the battery cell (11). If the controller (140) determines that the second point is not the end point of the constant voltage charging section, it can change the first point and the second point while maintaining the interval between the first point and the second point. According to an embodiment, the controller (140) can change to a point obtained by adding a preset time to each of the first point and the second point.

[0062] As the controller (140) changes the first time point and the second time point, the first point (201) corresponding to the first time point among the current line (200), the second point (202) corresponding to the second time point among the current line (200), the third point (301) corresponding to the first time point among the temperature line (300), and the fourth point (302) corresponding to the second time point among the temperature line (300) may also be changed together.

[0063] The controller (140) can compare the current value of the first point (201) and the current value of the second point (202), which are newly defined by changing the first point and the second point. According to the embodiment, the controller (140) can determine that the battery cell (11) is abnormal if the current value of the second point (202) is greater than the current value of the first point (201). That is, since the fact that the current value of the second point (202) is greater than the current value of the first point (201) implies that there is a section in the constant voltage charging section where the current value increases as time passes, the controller (140) can determine that the battery cell (11) is abnormal. In this case, lithium deposition occurs inside the battery cell (11), and current is supplied to the deposited lithium, so that electrical energy is converted into thermal energy and the battery cell (11) can generate heat. Therefore, the temperature value of the fourth point (302) may be higher than the temperature value of the third point (301).

[0064] The controller (140) can compare the current value at the first point (201) and the current value at the second point (202), and repeat the operation of changing the first point and the second point. Through this, the controller (140) can analyze the state of the current over the entire constant voltage charging section of the battery cell (11) and determine the increase in current due to lithium deposition inside the battery cell (11).

[0065] Accordingly, the battery diagnostic device (100) including the controller (140) can diagnose the condition of the battery cell (11) by analyzing current data during the constant voltage charging period. And, if the diagnosis result confirms 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 the user terminal through a communication unit (not shown), and can also provide information about the abnormal battery cell through a display equipped in a vehicle or charger, etc.

[0066] Accordingly, by analyzing the current data of the battery cell (11) with the battery diagnostic device (100), it is possible to perform early inspection of the abnormal battery cell (11) and replace the battery cell (11), and prevent a fire caused by overheating of the battery cell (11).

[0067] FIG. 6 is a flowchart showing a battery diagnostic method according to one embodiment disclosed in this document.

[0068] The embodiment illustrated in FIG. 6 is merely one embodiment, and the order of operations according to various embodiments of the present invention may differ from that illustrated in FIG. 6, and some steps illustrated in FIG. 6 may be omitted, the order of steps may be changed, or steps may be merged.

[0069] Referring to FIG. 6, the battery diagnostic method may include an operation of acquiring current data of a battery cell (S110), an operation of extracting an alternating current 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 alternating current component (S130), and an operation of determining the state of the battery cell based on the current values ​​of the first time point and the second time point (S140).

[0070] The above operations S110 to S140 will be explained in detail below with reference to FIGS. 1 to 5.

[0071] In operation S110, the battery diagnostic device (100) can obtain current data of the battery cell (11).

[0072] According to an embodiment, the battery diagnostic device (100) may 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) may 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 battery diagnostic device (100) may be connected to the battery cell (11).

[0073] The battery diagnostic device (100) can generate a graph representing data of the battery cell (11) during a constant voltage charging period. That is, the battery diagnostic device (100) can generate a graph in which the first axis represents time and the second axis represents current, voltage, and temperature values ​​based on the data of the battery cell (11) during a 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 starting 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.

[0074] After operation S110, operation S120 can be performed.

[0075] In operation S120, the battery diagnostic device (100) can extract an alternating current component from the current data. To do this, 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 direct current component of the current data. That is, the battery diagnostic device (100) can use the moving average line (203) to distinguish the current data into a direct current component and an alternating current component.

[0076] The battery diagnostic device (100) can extract the alternating current 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) can calculate the difference between the current value contained in the current data and the value represented by the moving average line (203) of the current data for each charging time, and connect them to extract the alternating current component of the current data corresponding to each time. In other words, the battery diagnostic device (100) can define the difference between the direct current data and the moving average line (203) of the direct current data as the alternating current 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 alternating current component, the center value of the alternating current component may be 0.

[0077] After operation S120, operation S130 can be performed.

[0078] In operation S130, the battery diagnostic device (100) can set a first time point and a second time point using a time interval obtained based on an alternating current component.

[0079] The battery diagnostic device (100) can calculate the standard deviation of the alternating current component of the current data. In the constant voltage charging section of an ideal 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) can be 0. Since the frequency is 0, the impedance of the battery cell (11) has a constant value, and accordingly, the current of the battery cell (11) can have only a DC component.

[0080] Accordingly, the alternating current 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 of the charger / discharger itself.

[0081] Due to noise in the current data, the current data of the battery cells (11) in the constant voltage charging section may be measured as increasing in some sections. Therefore, if the noise is large, two points in time must be selected with an interval large enough to ignore the noise, and the current values ​​at the two points in time must be compared. That is, the interval between the two points in time for comparing current data when the noise is large may be larger than the interval when the noise is small.

[0082] To this end, the battery diagnostic device (100) can match the standard deviation of the alternating current component of the current data with the interval between two points in time for comparison of the current data. According to an embodiment, the battery diagnostic device (100) can set the standard deviation of the alternating current component to be proportional to the interval between two points in time and generate a lookup table that corresponds to it one-to-one. That is, the battery diagnostic device (100) can pre-set a lookup table that matches the standard deviation of the alternating current component with the interval between two points in time, calculate the standard deviation of the alternating current component of the battery cell (11), and obtain the interval between two points in time corresponding to it on the lookup table.

[0083] After operation S130, operation S140 can be performed.

[0084] 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 time point and the second time point. The battery diagnostic device (100) can determine the state of the battery cell (11) by comparing the current value corresponding to the first time point and the current value corresponding to the second time point. This will be described in detail later in FIG. 7.

[0085] FIG. 7 is a flowchart specifically showing the operation of determining the state of a battery cell (11) based on the current values ​​at the first and second time points of FIG. 6.

[0086] Referring to FIG. 7, the operation of determining the state of a battery cell based on current values ​​at a first time point and a second time point may include an operation of determining whether the current value at the second time point is greater than the current value at the first time point (S141), an operation of determining whether the second time point is a time when charging is complete (S142), an operation of changing the first time point and the second time point (S143), an operation of determining the battery cell as normal (S144), and an operation of determining the battery cell as abnormal (S145).

[0087] In operation S141, the battery diagnostic device (100) can set a first time point defined on the time axis of a graph and a second time point which is a time point after a predetermined amount of time has elapsed from 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 that has elapsed from the first time point by the interval between the two time points obtained in FIG. 5.

[0088] The point corresponding to the first time point among the current lines (200) of the graph can be defined as the first point (201). The point corresponding to the second time point among the current lines (200) of the graph can be defined as the second point (202).

[0089] 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 the magnitude of the current value at the first point (201) and the current value at the second point (202). If the battery diagnostic device (100) determines that the current value at the second point is greater than the current value at the first point, operation S145 can be performed. If the battery diagnostic device (100) determines that the current value at the second point is less than the current value at the first point, operation S142 can be performed.

[0090] In operation S142, the battery diagnostic device (100) can determine whether the second point in time is the point of completion of charging. That is, if 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 point in time is the end point of the constant voltage charging section.

[0091] If the battery diagnostic device (100) determines that the second point in time is the point of completion of charging, operation S114 may be performed. If the battery diagnostic device (100) determines that the second point in time is not the point of completion of charging, operation S143 may be performed.

[0092] 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 preset 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.

[0093] After operation S143, operation S141 can be performed.

[0094] In operation S144, the battery diagnostic device (100) can determine that the battery cell (11) to be diagnosed is normal. When the battery diagnostic device (100) diagnoses the battery cell (11) from the constant voltage charging point to the charging end point while changing the first time point and the second time point, and the result is that 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.

[0095] In operation S145, the battery diagnostic device (100) can determine that the battery cell (11) to be diagnosed is abnormal. That is, the battery diagnostic device (100) can determine that the battery cell (11) is abnormal if it determines that the current value at the second time point is greater than the current value at the first time point.

[0096] In other words, the fact that the current value at the second point (202) is greater than the current value at the first point (201) indicates that there is a section in the constant voltage charging section where the current value increases as time passes, so 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), and current is supplied to the deposited lithium, so that electrical energy is converted into thermal energy and the battery cell (11) can generate heat. Accordingly, the temperature of the battery cell (11) may rise rapidly.

[0097] FIG. 8 shows a computing system that executes a battery diagnostic method according to one embodiment disclosed in this document.

[0098] Referring to FIG. 8, a computing system (400) according to one embodiment disclosed in this document may include an MCU (410), memory (420), input / output I / F (430) and communication I / F (440).

[0099] The MCU (410) may be a processor that executes various programs stored in memory (420) (e.g., SOH calculation program, cell balancing target determination program, etc.), processes various data including SOC, SOH, etc. of multiple battery cells through these programs, and performs the functions of the battery diagnostic device (100) described with reference to FIGS. 1 to 7. The MCU (410) may be a BMS, a separate PC, or a cloud, but is not limited thereto.

[0100] The memory (420) can store various programs regarding the calculation of the battery cell's SOH and the determination of the target for cell balancing. Additionally, the memory (420) can store various data such as the SOC and SOH data of each battery cell.

[0101] These memories (420) may be provided in multiple quantities as needed. The memories (420) may be volatile memories or non-volatile memories. As volatile memories, the memory (420) may use RAM, DRAM, SRAM, etc. As non-volatile memories, the memory (420) may use ROM, PROM, EAROM, EPROM, EEPROM, flash memory, etc. The examples of the memories (420) listed above are merely examples and are not limited to these examples.

[0102] The input / output I / F (430) can provide an interface that enables data transmission and reception between an input device (not shown), such as a keyboard, mouse, or touch panel, an output device (not shown), and an MCU (410).

[0103] The communication I / F (440) is configured to transmit and receive various data to and from a server and may be various devices capable of supporting wired or wireless communication. For example, through the communication I / F (440), programs for calculating the SOH of a battery cell or determining a balancing target, or various data, can be transmitted and received from a separately provided external server.

[0104] As such, a battery management method according to one embodiment disclosed in this document can be recorded in memory (420) and executed by an MCU (410).

[0105] The above description is merely an illustrative explanation of the technical concept disclosed in this document, and a person skilled in the art to which the embodiments disclosed in this document belong may make various modifications and variations within the scope of the essential characteristics of the embodiments disclosed in this document.

[0106] Accordingly, the embodiments disclosed in this document are intended to illustrate, not limit, the technical concept disclosed in this document, and the scope of the technical concept disclosed in this document is not limited by these embodiments. The scope of protection of the technical concept disclosed in this document shall be interpreted by the claims below, and all technical concepts within an equivalent scope shall be interpreted as being included within the scope of rights of this document. Explanation of the symbols

[0107] 100: Battery Diagnostic Device 110: Power supply 120: Information Acquisition Department 130: Storage section 140: Controller

Claims

Claim 1 A battery diagnostic device comprising: an information acquisition unit for acquiring current data including current values ​​over time in a constant voltage charging section of a battery cell; and a controller for setting a first time point at which the current data is acquired and a second time point at which the current data is acquired after a predetermined time has elapsed from the first time point, and determining the state of the battery cell based on whether the current value at the first time point exceeds the current value at the second time point. Claim 2 In claim 1, the controller is a battery diagnostic device that determines the battery cell as an abnormal battery cell when the current value at the second time point exceeds the current value at the first time point. Claim 3 A battery diagnostic device according to claim 2, wherein the controller changes the first time point and the second time point while maintaining a time interval between the first time point and the second time point, and compares the current value of the first time point with the current value of the second time point. Claim 4 In claim 2, the abnormal battery cell is a battery diagnostic device comprising a battery cell in which lithium (Li) is precipitated inside the battery cell. Claim 5 In claim 1, the controller is a battery diagnostic device that separates the current data into a DC component and an AC component using the moving average of the current data. Claim 6 In claim 5, the controller is a battery diagnostic device that extracts the alternating current component by removing the direct current component from the current data. Claim 7 In claim 6, the battery diagnostic device wherein the controller calculates the standard deviation of the alternating current component and sets the time interval between the first time point and the second time point based on the standard deviation. Claim 8 A battery diagnostic device according to claim 1, further comprising a storage unit that stores current data of the battery cell measured by the information acquisition unit. Claim 9 A battery diagnostic method comprising: a step of acquiring current data including current values ​​over time in a constant voltage charging section of a battery cell; a step of setting a first time point and a second time point after a predetermined time has elapsed from the first time point using a time interval acquired based on the alternating current component of the current data; and a step of determining the state of the battery cell based on whether the current value at the first time point exceeds the current value at the second time point. Claim 10 A battery diagnostic method according to claim 9, wherein the step of determining the state of the battery cell is a step of determining the battery cell as an abnormal battery cell when the current value at the second time point exceeds the current value at the first time point. Claim 11 A battery diagnostic method according to claim 10, wherein the abnormal battery cell comprises a battery cell in which lithium (Li) is precipitated inside the battery cell. Claim 12 A battery diagnostic method according to claim 9, wherein the step of determining the state of the battery cell comprises the step of generating a graph in which the first axis is time and the second axis is current value based on the current data, changing the first time point and the second time point while maintaining the time interval between the first time point and the second time point defined in the graph, and comparing the current value of the first time point and the current value of the second time point. Claim 13 A battery diagnostic method according to claim 9, wherein the step of setting the time interval includes the step of separating the current data into a DC component and an AC component using the moving average of the current data. Claim 14 A 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 distinguishing. Claim 15 A battery diagnostic method according to claim 14, wherein the step of setting the time interval comprises calculating the standard deviation of the alternating current component after the step of extracting the alternating current 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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