Patent Publication Number: US-2022229122-A1

Title: Battery diagnosis apparatus and method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Korean Patent Application No. 10-2019-0113169, filed on Sep. 11, 2019, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
     TECHNICAL FIELD 
     The present invention relates to a battery diagnosis apparatus and method, and more particularly, to a battery diagnosis apparatus and method for detecting a sudden drop in voltage during the charge and discharge of a battery. 
     BACKGROUND ART 
     Recently, research and development for secondary batteries have been actively conducted. Here, a, secondary battery is a battery which may be charged/discharged, and includes all of typical Ni/Cd batteries, Ni/MH batteries, and the like and recent lithium ion batteries. A lithium ion battery among secondary batteries has an advantage in that the energy density thereof is much higher than that of typical Ni/Cd batteries, Ni/MH batteries, and the like. Also, a lithium ion battery may be manufactured small and lightweight, and thus, is used as a power source of mobile devices. In addition, a lithium ion battery has attracted attention as a next generation energy storage medium since the range of use thereof has been expanded to being a power source of electric vehicles. 
     In addition, a secondary battery is generally used as a battery pack including a battery module in which a plurality of battery cells are connected in series and/or in parallel. In addition, the state and operation of a battery pack is managed and controlled by a battery management system. 
     If an abnormality occurs, such as an insulation error of the battery pack or an internal short of the battery cell itself, the cell voltage of the battery module may suddenly drop. At this time, typically, a method of diagnosing by detecting whether or not there is a voltage drop using a voltage difference (slope) from a previous time in a state in which no current flows (Rest) has been used, and thus, it is absolutely necessary to have a separate current sensor for determining the state in which no current flows. 
     DISCLOSURE OF THE INVENTION 
     Technical Problem 
     An aspect of the present invention provides a battery diagnosis apparatus capable of diagnosing a voltage abnormality of a battery cell by using a voltage variation of the battery cell without a separate current sensor, thereby detecting an abnormality due to a sudden voltage drop of a battery not only in a state in which the voltage of the battery does not flow (Rest) but also during the charge and discharge of the battery. 
     Technical Solution 
     According to an aspect of the present invention, there is provided a battery diagnosis apparatus for diagnosing a battery including battery cells, the apparatus including a voltage measurer configured to measure the voltage of each battery cell during a preset period of time, a voltage variation calculator configured to calculate an individual voltage variation of each battery cell during the preset period of time, an average voltage variation calculator configured to calculate an average voltage variation of the battery cells during the preset period of time, and an abnormality detector configured to determine that a voltage abnormality has occurred in at least one battery cell among the battery cells when a difference between the voltage variation of the at least one battery cell and the average voltage variation of the at least one battery cell is greater than a threshold value. 
     The voltage variation calculator of the battery diagnosis apparatus according to an embodiment of the present invention may calculate a voltage variation of each battery cell during the charge or discharge of the battery cells. 
     The voltage variation calculator of the battery diagnosis apparatus according to an embodiment of the present invention may calculate the voltage variation of each battery cell in a state in which no current flows in each battery cell. 
     The threshold value of the battery diagnosis apparatus according to an embodiment of the present invention may be set according to the manufacturer-specific specifications of each battery cell. 
     The threshold value of the battery diagnosis apparatus according to an embodiment of the present invention may be set according to the manufacturer-specific specifications of the voltage measurer. 
     The voltage variation calculator of the battery diagnosis apparatus according to an embodiment of the present invention may calculate the voltage variation of each battery cell in a section in which the state of charge (SOC) of each battery cell is equal to or greater than a preset reference value. 
     The preset reference value of the battery diagnosis apparatus according to an embodiment of the present invention may be set according to the type of each battery cell. 
     According to another aspect of the present invention, there is provided a battery diagnosis method for diagnosing a battery, the battery including battery cells, the method including measuring the voltage of each battery cell during a preset period of time, calculating an individual voltage variation of each battery cell during the preset period of time, calculating an average voltage variation of the battery cells during the preset period of time, and determining that a voltage abnormality has occurred in at least one battery cell among the battery cells when a difference between the voltage variation of the at least one battery cell and the average voltage variation of the at least one battery cell is greater than a threshold value. 
     Effects of the Invention 
     According to a battery diagnosis apparatus of the present invention, a voltage abnormality of a battery cell is diagnosed by using a voltage variation of the battery cell without a separate current sensor. Therefore, it is possible to detect an abnormality due to a sudden voltage drop of a battery not only during the charge and discharge of the battery but also in a rest state in which the voltage of the battery does not flow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram showing a typical configuration of a battery control system; 
         FIG. 2  is a block diagram showing a configuration of a battery diagnosis apparatus according to an embodiment of the present invention; 
         FIG. 3  is a diagram showing that a diagnosis experiment has performed on a defective cell through a battery diagnosis apparatus according to an embodiment of the present invention when a battery is being charged; 
         FIG. 4  is a diagram showing that a diagnosis experiment has performed on a defective cell through a battery diagnosis apparatus according to an embodiment of the present invention when a battery is in a rest state; 
         FIG. 5  is a flowchart showing a battery diagnosis method according to an embodiment of the present invention; and 
         FIG. 6  is a diagram showing a configuration of hardware according to an embodiment of the present invention. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present document, like reference numerals are used for like elements throughout the drawings, and redundant descriptors of the like elements are omitted. 
     For the various embodiments of the present invention disclosed in the present document, specific structural to functional descriptions are merely illustrative of the present invention. The various embodiments of the present invention may be embodied in various forms and should not be construed as limited to the embodiments set forth herein. 
     Terms such as “a first,” “a second,” “first,” and “second” used in various embodiments may modify various components regardless of the order and/or importance thereof, and do not limited the corresponding components. For example, a first component may be referred to as a second component without departing from the scope of the present invention, and similarly, a second component may also be referred to as a first component. 
     The terms used in this document are only used to describe specific embodiments, and may not be intended to limit the scope of other embodiments. Singular expressions may include plural expressions unless the context clearly indicates otherwise. 
     All the terms used herein, including technical or scientific terms, may have the same meanings as those commonly understood by those skilled in the art of the present invention. Terms that are defined in a dictionary commonly used should be interpreted as having the same or similar meaning to the meaning in the context of the related art, and should not be interpreted as having an ideal or overly formal meaning unless explicitly defined in the present document. In some cases, even the terms defined in this document should not be interpreted as excluding embodiments of the present invention. 
       FIG. 1  is a block diagram showing a typical configuration of a battery control system. 
     Specifically,  FIG. 1  is a configuration diagram schematically showing a battery control system including a battery pack  1  according to an embodiment of the present invention and a higher-level controller  2  included in a higher-level system. 
     As illustrated in  FIG. 1 , the battery pack  1  is composed of one or more battery cells and includes a battery module  10  chargeable and dischargeable, a switching unit  14  connected in series to a +terminal side or a −terminal side of the battery module  10  to control the charge/discharge current flow of the battery module  10 , and a battery management system (BMS)  20  for controlling and managing by monitoring the voltage, current, temperature, and the like of the battery pack  1  to prevent overcharging, overdischarging, and the like. 
     Here, the switching unit  14  is a semiconductor switching element for controlling a current flow for the charge or discharge of the battery module  10 , and for example, at least one MOSFET may be used. 
     In addition, the BMS  20  may measure or calculate the voltage and the current of a gate, a source, a drain, and the like of the semiconductor switching element in order to monitor the voltage, current, temperature, and the like of the battery pack  1 . In addition, using a sensor  12  provided adjacent to the semiconductor switching element  14 , the voltage, current, temperature, and the like of the battery pack  1  may be measured. The BMS  20  is an interface which receives measurement values of various parameters described above are input, and may include a plurality of terminals, a circuit connected to the terminals to process input values, and the like. 
     In addition, the BMS  20  may control the ON/OFF of the switching element  14 , for example MOSFET, and may be connected to the battery module  10  to monitor the state of the battery module  10 . 
     The higher-level controller  2  may transmit a control signal for the battery module  10  to the BMS  20 . Accordingly, the operation of the BMS  20  may be controlled on the basis of a signal applied from the higher-level controller  2 . A battery cell of the present invention may be a component included in a battery pack used in an energy storage system (ESS), a vehicle, or the like. However, the battery cell is not limited to such uses. 
     The configuration of the battery pack  1  and the configuration of the BMS  20  described above are known in the art, and thus, detailed descriptions thereof will be omitted. 
       FIG. 2  is a block diagram showing a configuration of a battery diagnosis apparatus according to an embodiment of the present invention. 
     Referring to  FIG. 2 , a battery diagnosis apparatus  200  according to an embodiment of the present invention may include a voltage measurement unit  210 , a voltage variation calculation unit  220 , an average voltage variation calculation unit  230 , and an abnormality detection unit  240 . 
     The voltage measurement unit  210  may measure the voltage of each battery cell during a preset period of time. For example, the voltage measurement unit  210  may be a measurement circuit included in the above-described battery management system BMS. 
     The voltage variation calculation unit  220  may calculate an individual voltage variation of each battery cell measured by the voltage measurement unit  210  during the preset period of time. For example, when the voltage of a battery cell is measured at 2 second intervals in the voltage measurement unit  210 , the voltage variation calculation unit  220  may calculate an individual voltage variation of each battery cell for two seconds. However, this is only exemplary. The time interval may be arbitrarily set by a user. 
     Particularly, the voltage variation calculation unit  220  may calculate a voltage variation of each battery cell not only in a state in which no current flows in the battery cell (rest) but also during the charge or discharge of the battery cell. Therefore, typically, it is absolutely necessary to have a current sensor to confirm the rest state of a battery. However, the battery diagnosis apparatus  200  according to an embodiment of the present invention may detect a sudden voltage drop only by using a battery voltage variation without having to determine the rest state of the battery through a current sensor. 
     In addition, the voltage variation calculation unit  220  may calculate the voltage variation of each battery cell for a section in which the state of charge (SOC) of the battery cell is equal to or greater than a preset reference value. This is because the resistance of a battery itself increases in a section in which the SOC of the battery is low, so that the deviation of the Direct Current Internal Resistance (DCIR) may be increased. At this time, the reference value of the SOC may be set according to the type of a battery cell. 
     The average voltage variation calculation unit  230  may calculate an average voltage variation of a plurality of battery cells during a preset period of time. For example, the average voltage variation calculation unit  230  may calculate the average voltage variation of all battery cells included in a specific battery pack during a preset period of time. 
     The abnormality detection unit  240  may determine that a voltage abnormality has occurred in a corresponding battery cell when there is a battery cell having a difference between the individual voltage variation calculated in the voltage variation calculation unit  220  and the average voltage variation calculated in the average voltage variation calculation unit  230  being greater than a threshold value. 
     That is, the abnormality detection unit  240  may detect a voltage abnormality of a battery according to the following equation. 
       Δ V   cell,each   −ΔV   cell,average   =V   threshold   [Equation 1]
 
     At this time, a current SOC value&gt;SOC threshold    
     In this case, the threshold value of the abnormality detection unit  240  may be set according to the manufacturer-specific specifications of the battery cell and the voltage measurement unit  210 . For example, the threshold value may be set in consideration of a voltage measurement error of the voltage measurement unit  210 , a capacity error between battery cells generated during the assembly of a battery module, and the like. 
     Meanwhile, although in  FIG. 2 , the battery diagnosis apparatus  200  according to an embodiment of the present invention may further include a memory unit for storing an individual voltage variation of each battery cell and an average voltage variation of the plurality of battery cells. 
     As described above, a battery diagnosis apparatus according to an embodiment of the present invention is capable of diagnosing a voltage abnormality of a battery cell by using a voltage variation of the battery cell without a separate current sensor, thereby detecting an abnormality due to a sudden voltage drop of a battery not only in a rest state in which the voltage of the battery does not flow but also during the charge and discharge of the battery. 
       FIG. 3  is a diagram showing that a diagnosis experiment has performed on a defective cell through a battery diagnosis apparatus according to an embodiment of the present invention when a battery is being charged. 
     Referring to  FIG. 3 , the horizontal axis represents time (seconds), the vertical axis (left) represents a voltage, and the vertical axis (right) represents a current. In addition, the graph of  FIG. 3  represents the voltage of a normal battery cell, the voltage of a defective battery cell, the average voltage of a plurality of cells, and the charge current of a battery, each measured in a charge state. 
     As shown in  FIG. 3 , the average voltage variation of a battery cell, the voltage variation of a normal battery cell, and the voltage variation of a defective battery cell for one second may be represented as follows. In addition, a threshold value when diagnosing an abnormal voltage drop of a battery was set to 15 mV. Meanwhile, in  FIG. 3 , the time interval is set to one second and the threshold value is set to 15 mV. However, a user may arbitrarily set the time interval and the threshold value. 
     Average voltage variation of battery cell: 
     ΔV cell, average =0 V (4.083 V No change) 
     Voltage variation of normal battery cell: 
     ΔV cell, normal =4.097 V−4.098 V=−0.001 V 
     |−0.001 V−0 V|&lt;Threshold value (15 mV) 
     Voltage variation of defective battery cell: 
     ΔV cell, abnormal =4.123 V−4.095 V=0.028 V 
     |0.028 V−0 V|&gt;Threshold value (15 mV) 
     As described above, in the case of the normal battery cell, the difference between the individual voltage variation and the average voltage variation is less than the threshold value, so that it is not determined as an abnormal voltage drop. However, in the case of the defective battery cell, the difference between the individual voltage variation and the average voltage variation is greater than the threshold value, so that it may be determined as an abnormal voltage drop. 
       FIG. 4  is a diagram showing that a diagnosis experiment has performed on a defective cell through a battery diagnosis apparatus according to an embodiment of the present invention when a battery is in a rest state. 
     Referring to  FIG. 4 , the horizontal axis represents time (seconds), the vertical axis (left) represents a voltage, and the vertical axis (right) represents a current. In addition, the graph of  FIG. 4  represents the voltage of a normal battery cell, the voltage of a defective battery cell, the average voltage of a plurality of cells, and the charge current of a battery, each measured in a rest state. 
     In  FIG. 4  also, as in the case of  FIG. 3 , the average voltage variation of a battery cell, the voltage variation of a normal battery cell, and the voltage variation of a defective battery cell for one second may be represented as follows. In addition, a threshold value when diagnosing an abnormal voltage drop of a battery was set to 15 mV. 
     Average voltage variation of battery cell: 
     ΔV cell, average =0 V (4.142 V No change) 
     Voltage variation of normal battery cell: 
     ΔV cell, normal =0 V 
     |0 V−0 V|&lt;Threshold value (15 mV) 
     Voltage variation of defective battery cell: 
     ΔV cell, abnormal =4.123 V−4.095 V=0.028 V 
     |0.028 V−0 V|&gt;Threshold value (15 mV) 
     As described above, in the case of the normal battery cell, the difference between the individual voltage variation and the average voltage variation is less than the threshold value, so that it is not determined as an abnormal voltage drop. However, in the case of the defective battery cell, the difference between the individual voltage variation and the average voltage variation is greater than the threshold value, so that it may be determined as an abnormal voltage drop. 
     As described above, the battery diagnosis apparatus according to an embodiment of the present invention is capable of detecting an abnormal voltage drop of a battery cell during the charge/discharge of a battery without having to confirm whether the battery is in a rest state through a current sensor. 
       FIG. 5  is a flowchart showing a battery diagnosis method according to an embodiment of the present invention. 
     Referring to  FIG. 5 , first, the voltage of each battery cell is measured during a preset period of time S 510 . At this time, a period of time during which the voltage of a battery cell is measured may be arbitrarily set by a user. 
     Thereafter, an individual voltage variation of each battery cell during a preset period of time is calculated S 520 . In Step S 520 , it is possible to calculate the voltage variation of each battery cell not only in a rest state in which no current flows in the battery cell but also during the charge or discharge of the battery cell. 
     Next, an average voltage variation of a plurality of battery cells during the preset period of time is calculated S 530 . At this time, the average voltage variation of all battery cells included in a specific battery pack may be calculated. 
     In addition, in Step S 520  and in Step S 530 , in order to reduce the effect due to the resistance of a battery itself, the voltage variation of each battery cell is calculated for a section in which the SOC of the battery cell is equal to or greater than a reference value. 
     Thereafter, when there is a battery cell having a difference between the individual voltage variation calculated in Step S 520  and the average voltage variation calculated in Step S 530  being greater than a threshold value, it is determined that a voltage abnormality has occurred in a corresponding battery cell S 540 . 
     In this case, the threshold value of Step S 540  may be set according to the manufacturer-specific specifications of the battery cell and a voltage measurement unit (for example, the battery management system BMS). For example, the threshold value may be set in consideration of a voltage measurement error of the voltage measurement unit, a capacity error between battery cells generated during the assembly of a battery module, and the like. 
     As described above, according to the method for diagnosing a battery according to an embodiment of the present invention, a voltage abnormality of a battery cell is diagnosed by using a voltage variation of the battery cell without a separate current sensor. Therefore, it is possible to detect an abnormality due to a sudden voltage drop of a battery not only during the charge and discharge of the battery but also in a rest state in which the voltage of the battery does not flow. 
       FIG. 6  is a diagram showing a configuration of hardware according to an embodiment of the present invention. 
     As shown in  FIG. 6 , a battery management apparatus  600  may have a micro-controller (MCU)  610  for controlling various processing and each component, a memory  620  in which an operating system program, various programs (for example, a battery pack abnormality diagnosis program or a battery pack temperature estimation program), and the like are stored, an input/output interface  630  for providing an input interface and an output interface between a battery cell module and/or a switching unit (for example, a semiconductor switching element), and a communication interface  640  capable of communicating with the outside (for example, a higher-level controller) through a wired/wireless communication network. As described above, a computer program according to the present invention is stored in the memory  620  and processed by the micro-controller  610 , and thus, may be implemented as, for example, a module which performs each functional block illustrated in  FIG. 2 . 
     In the above, even if all the components constituting the embodiments of the present invention have been described as being combined or combined to operate as one, the present invention is not necessarily limited to these embodiments. That is, if within the scope of the present invention, all of the components may be selectively combined and operated as one or more. 
     In addition, the terms “include,” “consist,” or “have” as described above mean that a corresponding component may be intrinsic, unless specifically stated otherwise, and it should interpreted as including other components rather than excluding other components. All terms including technical or scientific terms have the same meanings as those commonly understood by those skilled in the art to which the present invention pertains, unless defined otherwise. Terms commonly used as those defined in a commonly used dictionary should be construed as being consistent with the context of the relevant art, and are not to be construed in an idealized or overly formal sense unless expressly defined in the present invention. 
     The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and variations without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical spirit of the present invention, but to explain, and the scope of the technical spirit of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed by the following claims, and all technical concepts within the scope of the present invention should be construed as being included within the scope of the rights of present invention.