Battery diagnostic apparatus and battery system

Abstract

A battery diagnostic apparatus and a battery system. The utility model relates to a method for diagnosing defects of a battery, battery diagnosis equipment for providing the method and a battery system for providing the method. The battery system provided by the utility model comprises the following components: a battery which comprises a plurality of battery units; a current sensor that measures a battery current, which is a current flowing in the battery, every predetermined period; and a battery management system (BMS) that calculates a current change amount between two battery currents measured in two adjacent periods among a plurality of periods in a constant voltage mode in which a battery voltage, which is a voltage across both ends of the battery, is constant while charging the battery during a charging cycle, and diagnosing a defect of the battery based on the current change amount.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of Korean Patent Application No. 10-2021-0159978 filed in the Korean Intellectual Property Office on November 19, 2021, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The utility model relates to a method for diagnosing (or testing) defects of a battery during the charging process of the battery, a battery diagnosis device providing the method and a battery system providing the method. Background Art

[0004] The constant current / constant voltage (CC / CV) charging method is a method for charging a lead storage battery, a lithium ion battery, or the like. Figure 6 It is a graph for explaining the change of battery voltage and the change of battery current during the conventional constant current / constant voltage (CC / CV) charging process.

[0005] Reference Figure 6 , in the charging start step, the charger charges the battery in constant current (CC) mode. When the constant current (CC) mode is continued, the voltage of the battery gradually increases. The constant current (CC) mode is a method in which the charger applies a constant current (CC) to the battery to charge the battery. Even if the battery voltage reaches the reference voltage (charging upper limit voltage) when charging the battery, the battery will not reach a fully charged state (100% charged state). Therefore, when the battery voltage reaches the reference voltage (charging upper limit voltage), the charger charges the battery in constant voltage (CV) mode. When the constant voltage (CV) mode is continued, the battery current gradually decreases. When the current decreases to near zero, the charger ends charging the battery.

[0006] If the battery is continuously charged in constant current (CC) mode, the battery voltage continues to rise, and problems such as battery explosion may eventually occur. Therefore, when the battery voltage reaches the upper limit voltage of charging, the charger switches from constant current (CC) mode to constant voltage (CV) mode to charge the battery. Then, the battery can be safely charged to a fully charged state (100% charged state). That is, since the capacity of the battery is limited, the battery voltage can be constantly maintained only when the charging current is reduced in the interval of charging the battery in constant voltage (CV) mode.

[0007] On the other hand, conventionally, there are many methods for diagnosing (detecting) abnormal batteries based on the amount of change (ΔV) in battery voltage. However, there is no method for diagnosing abnormal batteries based on the amount of change (ΔI) in battery current (eg, charging current). Utility Model Content

[0008] Technical issues

[0009] The utility model aims to provide a defect diagnosis method for a battery, a battery diagnosis device for providing a defect diagnosis method for a battery, and a battery system for providing a defect diagnosis method for a battery, so as to diagnose defects of the battery during charging the battery using a constant current / constant voltage (CC / CV) charging method.

[0010] Technical Solution

[0011] A battery system according to one aspect of the present invention includes: a battery including a plurality of battery cells; a current sensor that measures a battery current as a current flowing through the battery at predetermined intervals; and a battery management system (BMS) that calculates a current variation between two battery currents measured in two adjacent cycles among a plurality of cycles in a constant voltage mode of a charging cycle, and diagnoses a defect of the battery based on the current variation. In the constant voltage mode, the battery is charged so that a battery voltage as a voltage at both ends of the battery is constant.

[0012] The BMS may calculate the current variation in the constant voltage mode in each charging cycle by subtracting the value of the (N-1)th battery current measured in the (N-1)th cycle from the value of the Nth battery current measured in the Nth cycle, and when the current variation is zero or greater at least once in the charging cycle, the BMS may determine that an event has occurred in the charging cycle to increase the count by 1, and the BMS may diagnose a defect of the battery based on the accumulated counts of multiple charging cycles.

[0013] When the cumulative count exceeds a predetermined reference value, the BMS may diagnose that the battery is defective.

[0014] When the events continuously occur in the charging cycle and a cumulative count corresponding to the events continuously occurring exceeds a predetermined reference value, the BMS may diagnose that the battery is defective.

[0015] According to another aspect of the utility model, a battery diagnostic device includes: a charger, which charges a battery cell according to a predetermined charging method; a current sensor, which measures a cell current as a current flowing through the battery cell at a predetermined period; and a controller, which calculates a current change amount between two cell currents measured in two adjacent cycles among multiple cycles in a constant voltage mode of a charging cycle, and diagnoses a defect of the battery cell based on the current change amount. In the constant voltage mode, the battery cell is charged so that the cell voltage as the voltage at both ends of the battery cell is constant.

[0016] The controller can calculate the current change in the constant voltage mode in each charging cycle by subtracting the value of the (N-1)th cell current measured in the (N-1)th cycle from the value of the Nth cell current measured in the Nth cycle, and when the current change is zero or greater at least once in the charging cycle, the controller can determine that an event has occurred in the charging cycle to increase the count by 1, and the controller can diagnose the defect of the battery cell based on the cumulative counts of multiple charging cycles.

[0017] When the accumulated count exceeds a predetermined reference value, the controller may diagnose that the battery cell is defective.

[0018] The controller may diagnose that the battery cell is defective when the events continuously occur in the charging cycle and a cumulative count corresponding to the events that continuously occur exceeds a predetermined reference value.

[0019] According to another aspect of the utility model, a defect diagnosis method for a battery measures a battery current as a current flowing through a battery at predetermined intervals, and diagnoses defects in the battery based on the battery current, and the method includes the following steps: performing a constant voltage mode of a charging cycle, in which the battery is charged so that the battery voltage as the voltage at both ends of the battery is constant; and calculating a current change between two battery currents measured in two adjacent cycles among a plurality of cycles in the constant voltage mode, and diagnosing defects in the battery based on the current change.

[0020] The step of diagnosing a defect in the battery may include the following steps: calculating the current variation in the constant voltage mode by subtracting the value of the (N-1)th battery current measured in the (N-1)th cycle from the value of the Nth battery current measured in the Nth cycle; determining that an event occurs in the charging cycle when the current variation is zero or greater at least once in the charging cycle to increase the count by 1; and diagnosing the defect in the battery based on the accumulated counts of multiple charging cycles.

[0021] The step of diagnosing a defect in the battery based on the cumulative count of the charging cycles may include diagnosing that the battery is defective when the cumulative count exceeds a predetermined reference value.

[0022] The step of diagnosing a defect in the battery based on the cumulative count of the charging cycles may include diagnosing that the battery is defective when the event occurs continuously in the charging cycle and the cumulative count corresponding to the continuously occurring event exceeds a predetermined reference value.

[0023] Beneficial Effects

[0024] The utility model has the effect of diagnosing the defects of the battery in a simple way during the process of charging the battery.

[0025] The utility model has the effect of providing diversity in a method of diagnosing a defect of a battery by diagnosing the defect of the battery based on a change in the current of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a diagram for describing a battery system for diagnosing a defect of a battery connected to an external device (eg, a vehicle, etc.) according to an embodiment.

[0027] Figure 2 is a diagram illustrating a battery diagnosis apparatus for diagnosing a defect of a battery cell according to an embodiment.

[0028] Figure 3 and Figure 4 is a graph showing changes in cell current in a process of charging a predetermined defective battery cell using a constant current / constant voltage charging method.

[0029] Figure 5 is a flowchart illustrating a method for diagnosing a defect of a battery according to an embodiment.

[0030] Figure 6 A graph used to describe changes in battery voltage and changes in battery current during conventional constant current / constant voltage (CC / CV) charging. DETAILED DESCRIPTION

[0031] Hereinafter, the embodiments disclosed in this specification will be described in detail with reference to the accompanying drawings, and in this specification, the same or similar constituent elements will be represented by the same or similar reference numerals, and their redundant description will be omitted. The terms "module" and / or "unit, part or component" used in the following description to represent constituent elements are only used to make this specification easier to understand, and therefore, these terms do not have the meaning or function of distinguishing themselves from each other. In addition, when describing the embodiments of this specification, when it is determined that the detailed description of the known technology associated with the utility model may confuse the gist of the utility model, it will be omitted. In addition, the accompanying drawings are provided only to allow the embodiments disclosed in this specification to be easily understood and should not be construed as limiting the spirit disclosed in this specification, and it should be understood that the utility model includes all modifications, equivalents and substitutions without departing from the scope and spirit of the utility model.

[0032] Terms including ordinal numbers such as first, second, etc. will only be used to describe various constituent elements and should not be construed as limiting these constituent elements. The terms are only used to distinguish one constituent element from other constituent elements.

[0033] It should be understood that when one component is referred to as being “connected” or “coupled” to another component, it may be directly connected or coupled to the other component, or may be connected or coupled to the other component with another component interposed therebetween. Conversely, it should be understood that when an element is described as being “directly coupled” or “directly connected” to another element, there are no other elements between the element and the other element.

[0034] In the present application, it should be understood that the terms "comprises", "includes", "has" or "configuration" indicate the presence of the features, quantities, steps, operations, constituent elements, parts or combinations thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, quantities, steps, operations, constituent elements, parts or combinations.

[0035] Figure 1 is a diagram for describing a battery system for diagnosing a defect of a battery connected to an external device (eg, a vehicle, etc.) according to an embodiment.

[0036] Reference Figure 1 , the battery system A includes a battery 10 , a relay 20 , a current sensor (or current sensor) 30 , and a battery management system (hereinafter referred to as BMS) 40 .

[0037] The battery 10 may include a plurality of battery cells Cell1-Celln electrically connected in series and in parallel. In an embodiment, the battery cells may be rechargeable secondary batteries. A predetermined number of battery cells may be connected in series to form a battery module, a predetermined number of battery modules may be connected in series to form a battery pack, and a predetermined number of battery packs may be connected in parallel to form a battery bank, so that the battery bank supplies the desired power.

[0038] Although Figure 1 The battery 10 is shown in which three battery cells Cell1-Cell3 are connected in series, but the present invention is not limited thereto, and the battery 10 may include a plurality of battery cells Cell1-Celln connected in series and / or in parallel. In an embodiment, Figure 1 At least one of the three battery cells Cell1-Cell3 shown may be a defective abnormal cell. Hereinafter, a battery cell that meets a predetermined standard is defined as a normal cell, and a defective battery cell that does not meet the predetermined standard is defined as an abnormal cell. In addition, a battery 10 including at least one abnormal cell is defined as a defective battery 10 or an abnormal battery 10.

[0039] exist Figure 1 In the embodiment, the battery 10 includes a plurality of battery cells Cell1-Cell3 connected in series and connected between two output terminals OUT1 and OUT2 of the battery system A. The relay 20 is connected between the positive electrode of the battery system A and the first output terminal OUT1, and the current sensor 30 is connected between the negative electrode of the battery system A and the second output terminal OUT2. Figure 1 The components and the connection relationships between the components shown in the figure are examples, and the present invention is not limited thereto.

[0040] The relay 20 controls the electrical connection between the battery system A and the external device. When the relay 20 is turned on, the battery system A and the external device are electrically connected to perform charging or discharging, and when the relay 20 is turned off, the battery system A and the external device are electrically separated. In this case, the external device may be a charger that supplies power (or electricity) to the battery 10 to charge the battery 10 in a charging cycle, and may be a load to which the battery 10 discharges in a discharging cycle.

[0041] The current sensor 30 is connected in series to a current path between the battery 10 and an external device. The current sensor 30 may measure a battery current (ie, a charging current and a discharging current) flowing through the battery 10, and may transmit the measurement result to the BMS 40.

[0042] In an embodiment, the current sensor 30 may measure a battery current (ie, a charging current) at a predetermined period in a charging cycle in which the battery 10 is charged by power of an external device, and may transmit the measurement result to the BMS 40 .

[0043] The BMS 40 is electrically connected to each of the battery cells Cell1-Cell3 through wiring. The BMS 40 can collect and analyze various information related to the battery cells (including information about the battery cells Cell1-Cell3) so that the BMS controls charging, discharging, protection operations, etc. of the battery cells and the operation of the relay 20.

[0044] According to an embodiment, the BMS 40 may control charging of the battery 10 using a constant current / constant voltage (CC / CV) charging method, and may diagnose a defect of the battery based on an amount of change in current of the battery in a constant voltage (CV) mode.

[0045] The charging cycle to be described below may represent an interval from the time when the battery 10 starts charging to the time when the battery 10 reaches a fully charged state through charging. In the charging cycle, the charging mode may include a constant current (CC) mode and a constant voltage (CV) mode. In this case, the fully charged state of the battery does not mean that the state of charge (SOC) of the battery becomes 100%, and the fully charged state may be set to a charging state (e.g., 80% or 85%) in which the battery is safely used without being overcharged.

[0046] For example, for each charging cycle, the BMS 40 may receive a current value of a battery current (hereinafter referred to as a battery current value) from the current sensor 30 at a predetermined period. In the constant voltage (CV) mode, the BMS 40 generates a current signal corresponding to the Nth battery current value (I N ) is greater than or equal to the (N-1)th battery current value (I N-1 ) corresponding to the event (ΔI=I N -I N-1 ≥0) (hereinafter referred to as a current increase event) is counted. In this case, even when the event occurs multiple times in one charging cycle, the BMS 40 can increase the number of counts for each charging cycle. That is, even if the current increase event occurs three times in the constant voltage (CV) mode of the first charging cycle and the current increase event occurs twice in the constant voltage (CV) mode of the second charging cycle, the BMS 40 can determine that the current increase event occurs twice in total by occurring once in each of the first charging cycle and the second charging cycle.

[0047] In addition, when the sum of counts in a plurality of charging cycles exceeds a predetermined reference value (e.g., 5 times), the BMS 40 may diagnose that a defective battery cell exists in the battery 10. That is, the BMS 40 may diagnose the battery 10 as an abnormal battery. In this case, the abnormal battery may be a battery 10 including a defective battery cell. Figure 5 Provide a more detailed description.

[0048] Figure 2 is a diagram illustrating a battery diagnosis apparatus for diagnosing a defect of a battery cell according to an embodiment.

[0049] Reference Figure 2 , the battery diagnosis device B includes a relay 200 , a current sensor 300 , a charger 400 , and a controller (or control unit) 500 .

[0050] The battery diagnostic device B may be a device for diagnosing defects in the battery cell 100. For example, the battery diagnostic device B may be a device for diagnosing defects in the battery cell 100 in the final step of the manufacturing process of the battery cell 100. In this case, the battery cell 100 may be a rechargeable secondary battery. That is, the battery cell 100 may correspond to a battery cell 100 included in the battery cell 100. Figure 1 Each of the battery cells Cell1-Cell3 in the battery 10 is shown. In addition, the battery cell 100 may include a lead storage battery (12V) for supplying power to various electronic devices included in the battery system A.

[0051] The relay 200 controls the electrical connection between the battery cell 100 and the charger 400. When the relay 200 is turned on, the battery cell 100 and the charger 400 are electrically connected, thereby performing charging. When the relay 200 is turned off, the battery cell 100 and the charger 400 are electrically separated.

[0052] The current sensor 300 may be connected in series between the battery cell 100 and the charger 400 to measure a current (hereinafter referred to as a cell current) flowing in the battery cell 100, and may transmit the measurement result to the controller 500. According to an embodiment, the current sensor 300 may measure the cell current at a predetermined period in a charging cycle in which the battery cell 100 is charged by power of the charger 400, and may transmit the measurement result to the controller 500.

[0053] The controller 500 may control the relay 200 and the charger 400 to diagnose a defect in the battery cell 100 while charging the battery cell 100. According to an embodiment, the controller 500 may diagnose a defect of the battery cell 100 based on an amount of change in a cell current in a constant voltage (CV) mode while charging the battery cell 100 a plurality of times using a constant current / constant voltage (CC / CV) charging method.

[0054] For example, the controller 500 may receive a current value of a cell current (hereinafter referred to as a cell current value) from the current sensor 300 at a predetermined period in a constant voltage (CV) mode of each charging cycle. The controller 500 generates an Nth cell current value (I N ) is greater than or equal to the (N-1)th unit current value (I N-1 ) corresponding to the event (ΔI=I N -I N-1 ≥0) (hereinafter referred to as a current increase event). In this case, even when the event occurs multiple times in one charging cycle, the controller 500 can increase the number of counts for each charging cycle. That is, even if the current increase event occurs three times in the constant voltage (CV) mode of the first charging cycle and the current increase event occurs twice in the constant voltage (CV) mode of the second charging cycle, the controller 500 can count (or determine) that the current increase event occurs twice in total by occurring once in each of the first charging cycle and the second charging cycle. In addition, when the sum of the counts in multiple charging cycles exceeds a predetermined reference value (for example, 5 times), the controller 500 can diagnose that there is a defective battery cell in the battery cell 100. That is, the controller 500 can diagnose the battery cell 100 as an abnormal cell.

[0055] Figure 3 FIG. 1 is an example diagram of an experiment of observing current changes when the abnormal cell is charged by a constant current / constant voltage (CC / CV) charging method after an abnormal cell in which the anode terminal is not in contact with the lead wire is artificially manufactured.

[0056] Reference Figure 3 , for example, the charger 400 may charge the battery cell 100 in a constant current (CC) mode in interval a1, and when the cell voltage reaches a charge upper limit voltage, the charger 400 may charge the battery cell 100 in a constant voltage (CV) mode in interval a2.

[0057] Reference Figure 3When a defective battery cell is charged in constant voltage (CV) mode, a cell current jump phenomenon may occur. In this case, the cell current jump phenomenon is similar to the above-mentioned current increase event (ΔI = I N -I N-1 As a result of the experiment, it was confirmed in the 144th charging cycle out of a total of 200 charging cycles that Figure 3 The phenomenon shown in FIG. 1 and the average value of the cell current increase (ΔI) is 4.5 mA. In this case, the cell temperature and the cell voltage show changes within the normal range. That is, according to Figure 3 The experimental results show that abnormal cells can be distinguished by the change in cell current in the constant voltage (CV) interval.

[0058] Figure 4 is another example diagram of an experiment of observing current changes when charging the abnormal cell by a constant current / constant voltage (CC / CV) charging method after artificially manufacturing an abnormal cell in which the anode tab is not in contact with the lead wire.

[0059] Reference Figure 4 , for example, the charger 400 may charge the battery cell 100 in a constant current (CC) mode in interval b1, and when the cell voltage reaches a charge upper limit voltage, the charger 400 may charge the battery cell 100 in a constant voltage (CV) mode in interval b2.

[0060] Reference Figure 4 When a defective battery cell is charged in constant voltage (CV) mode, a cell current jump phenomenon may occur. In this case, the cell current jump phenomenon is similar to the above-mentioned current increase event (ΔI = I N -I N-1 As a result of the experiment, it was confirmed in the 164th charging cycle out of a total of 200 charging cycles that Figure 4 The phenomenon shown in FIG. 1 and the average value of the cell current increase (ΔI) is 1.5 mA. In this case, the cell temperature and the cell voltage show changes within the normal range. That is, according to Figure 4 The experimental results show that abnormal cells can be distinguished by the change in cell current in the constant voltage (CV) interval.

[0061] Based on these experimental results, reference Figure 1 , Figure 2 and Figure 5 A defect diagnosis method for a battery, a battery diagnosis device for providing a defect diagnosis method for a battery, and a battery system for providing a defect diagnosis method for a battery are described in detail. Figure 5A battery diagnostic apparatus B for diagnosing an abnormal battery and a battery system A for diagnosing a defect in a battery 10 including at least one abnormal battery are described together.

[0062] Figure 5 is a flowchart illustrating a method for diagnosing a defect of a battery according to an embodiment.

[0063] First, according to an embodiment, the BMS 40 turns on the relay 20 to electrically connect the external device to the battery 10 , and communicates with the external device so that the battery 10 is charged in a constant current (CC) mode ( S110 ).

[0064] The constant current (CC) mode is a mode in which an external device (e.g., a charger) applies a current having a predetermined constant current value (i.e., a constant current CC) to the battery 10 to charge the battery 10. When the constant current (CC) mode continues, the voltage across the battery 10 (hereinafter referred to as the battery voltage) gradually increases.

[0065] In another embodiment, reference Figure 2 and Figure 5 , the controller 500 turns on the relay 200 and controls the charger 400 to charge the battery cell 100 in a constant current (CC) mode ( S110 ).

[0066] Next, when the battery voltage reaches the charging upper limit voltage as a predetermined reference voltage (Yes in S130 ), the BMS 40 communicates with an external device so that the battery 10 is charged in a constant voltage (CV) mode ( S150 ).

[0067] Even if the battery voltage reaches the reference voltage (charging upper limit voltage) when the battery 10 is charged, the battery does not reach a fully charged state. Therefore, when the battery voltage reaches the reference voltage (charging upper limit voltage), the BMS 40 may communicate with an external device to charge the battery 10 in a constant voltage (CV) mode.

[0068] The constant voltage (CV) mode is a mode in which an external device (e.g., a charger) charges the battery 10 while maintaining a constant battery voltage. In this case, the external device may receive a battery voltage value from the BMS 40, or may check the voltage value across a link capacitor (not shown) connected in parallel to the battery 10 to check whether the battery voltage remains constant. In the constant voltage (CV) mode, the battery voltage value is constant, but the charging current gradually decreases as the constant voltage (CV) mode continues. When the charging current decreases to almost zero (0A), the external device ends charging the battery 10.

[0069] In another embodiment, reference Figure 2 and Figure 5, when the cell voltage reaches the charging upper limit voltage as a predetermined reference voltage (Yes in S130 ), the controller 500 controls the charger 400 to charge the battery cell 100 in a constant voltage (CV) mode ( S150 ).

[0070] Next, the BMS 40 diagnoses a defect in the battery 10 based on the current variation amount between the charging currents measured in two adjacent cycles in the constant voltage (CV) mode ( S170 ).

[0071] The current sensor 30 may measure the charging current every predetermined period and may transmit the measurement result to the BMS 40. Based on the measurement result, the BMS 40 may calculate the current variation amount between the charging currents measured in two adjacent periods in a constant voltage (CV) mode.

[0072] In step S170 , the BMS 40 determines whether the amount of change (ΔI) in the charging current is equal to or greater than zero (ΔI≧0) ( S171 ).

[0073] The BMS 40 receives a charging current value (battery current value) from the current sensor 30 at a predetermined cycle in a constant voltage (CV) mode. Whenever the BMS 40 receives a charging current value, the BMS 40 calculates a charging current value (I N ) and the previously received charging current value (I N-1 ) is the difference between the charging current change (ΔI = I N -I N-1 ≥0). In addition, the BMS 40 determines the change in the charging current (ΔI = I N -I N-1 ) is equal to or greater than zero (ΔI=I N -I N-1 That is, the case where the amount of change in the charging current (ΔI) is equal to or greater than zero (ΔI ≥ 0) may correspond to the Nth battery current value (I N ) is greater than or equal to the (N-1)th battery current value (I N-1 ) situation.

[0074] Reference Figure 3 and Figure 4 , the case where the amount of change (ΔI) of the charging current is equal to or greater than zero (ΔI≥0) may correspond to a phenomenon in which the cell current jumps in a constant voltage (CV) interval. The phenomenon in which the cell current jumps in a constant voltage (CV) interval may indicate that an abnormal cell is included in the battery 10.

[0075] Since the constant voltage (CV) mode is a charging method for charging the battery 10 while maintaining the battery voltage, the external device can supply a charging current in a stable state to the battery 10. Therefore, when a predetermined defective battery cell (hereinafter referred to as an abnormal cell) exists among the battery cells Cell1-Cell3, a change in the cell current (current jump phenomenon) caused by the abnormal cell may also affect the battery current flowing through the battery cell (i.e., the battery 10).

[0076] In step S170, if the change amount of the charging current is equal to or greater than zero as a result of the determination (No in S171), the BMS 40 waits until a charging current value (battery current value) corresponding to the next cycle is received (S172). When the next cycle is reached, the BMS 40 repeats step S171.

[0077] In step S170 , if it is determined that the change amount of the charging current is equal to or greater than zero (Yes in S171 ), the BMS 40 increments the count by 1 ( S173 ).

[0078] According to an embodiment, when a situation in which the amount of change (ΔI) of the charging current is equal to or greater than zero (ΔI≧0) occurs at least once in the Nth charging cycle, the BMS 40 increases the count by 1.

[0079] Even when an event occurs multiple times in the Nth charging cycle, the BMS 40 may increase the count number for each Nth charging cycle. For example, even if the case where the amount of change (ΔI) of the charging current is equal to or greater than zero (ΔI≥0) occurs three times in the 10th charging cycle, the BMS 40 may count the number of times the event occurs in the 10th charging cycle as 1 time. For another example, even if the case where the amount of change (ΔI) of the charging current is equal to or greater than zero (ΔI≥0) occurs three times in the 10th charging cycle and the case where the amount of change (ΔI) of the charging current is equal to or greater than zero (ΔI≥0) occurs twice in the 11th charging cycle, the BMS 40 may count the number of times the event occurs during the first charging cycle to the 11th charging cycle as a total of two events that occur by the event occurring once in each of the 10th charging cycle and the 11th charging cycle.

[0080] In step S170 , the BMS 40 diagnoses a defect in the battery 10 based on the cumulative count (or the cumulative count number) as a result of performing charging up to the Nth charging cycle ( S174 and S175 ).

[0081] According to an embodiment, when the cumulative count exceeds a predetermined reference value, the BMS 40 may diagnose that the battery 10 is defective. For example, a total of 12 charging cycles are repeated, and when it is determined in the 12th charging cycle that the cumulative count (e.g., 6 times) exceeds a reference value (e.g., 5 times), the battery 10 may be diagnosed as an abnormal battery.

[0082] According to another embodiment, if an event in which the amount of change (ΔI) of the charging current is equal to or greater than zero (ΔI≥0) occurs continuously in a plurality of charging cycles and a cumulative count corresponding to the event exceeds a predetermined reference value, the BMS 40 may diagnose that the battery 10 is defective.

[0083] For example, it is assumed that the event occurs in the 15th to 20th charging cycles while a total of 20 charging cycles are performed. Since the BMS 40 determines that 6 events occur continuously in the 15th to 20th charging cycles and the cumulative count (e.g., 6 times) exceeds the reference value (e.g., 5 times), the BMS 40 can diagnose the battery 10 as an abnormal battery.

[0084] In step S170 , if the cumulative count as a result of performing charging until the Nth charging cycle does not exceed the reference value (No in S174 ), the BMS 40 may repeat the method for diagnosing a defect of the battery from step S171 until charging is completed ( S176 ).

[0085] In another embodiment, reference Figure 2 and Figure 5 , the controller 500 calculates the change amount of the charging current (cell current) every predetermined period in the constant voltage (CV) mode, and diagnoses the defect of the battery cell 100 based on the charging current change amount (S170). That is, the controller 500 can diagnose the defect of the battery cell 100 by performing the above steps S171 to S176.

[0086] While the invention has been described in connection with what are presently considered to be practical embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but on the contrary, the invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A battery system, It is characterized in that The battery system comprises: A battery, the battery comprising a plurality of battery cells; a current sensor that measures a battery current as a current flowing through the battery at every predetermined period; and a battery management system BMS that calculates a current variation amount between two battery currents measured in two adjacent cycles among a plurality of cycles in a constant voltage mode of a charging cycle in which the battery is charged so that a battery voltage that is a voltage at both ends of the battery is constant, and diagnoses a defect of the battery based on the current variation amount, Wherein, for each charging cycle, the BMS receives the value of the battery current from the current sensor at a predetermined period.

2. The battery system according to claim 1, It is characterized in that the BMS calculating the current variation amount in the constant voltage mode in each charging cycle by subtracting a value of the (N-1)th battery current measured in the (N-1)th cycle from a value of the Nth battery current measured in the Nth cycle, Wherein, when the current variation is zero or greater occurs at least once in a charging cycle, the BMS determines that an event occurs in the charging cycle so that the count is increased by 1, and The BMS diagnoses defects of the battery based on a cumulative count of a plurality of charging cycles.

3. The battery system according to claim 2, It is characterized in that When the cumulative count exceeds a predetermined reference value, the BMS diagnoses that the battery is defective.

4. The battery system according to claim 2, It is characterized in that When the events continuously occur in the charging cycle and a cumulative count corresponding to the events continuously occurring exceeds a predetermined reference value, the BMS diagnoses that the battery is defective.

5. A battery diagnostic device, It is characterized in that The battery diagnostic device comprises: A charger, wherein the charger charges the battery unit according to a predetermined charging method; a current sensor that measures a cell current as a current flowing through the battery cell at a predetermined cycle; and a controller that calculates a current variation amount between two cell currents measured in two adjacent cycles among a plurality of cycles in a constant voltage mode of a charging cycle in which the battery cell is charged so that a cell voltage that is a voltage at both ends of the battery cell is constant, and diagnoses a defect of the battery cell based on the current variation amount, Wherein, for each charging cycle, the controller receives the value of the cell current from the current sensor at a predetermined period.

6. The battery diagnostic device according to claim 5, It is characterized in that the controller calculating the current variation amount in the constant voltage mode in each charging cycle by subtracting a value of the (N-1)th cell current measured in the (N-1)th cycle from a value of the Nth cell current measured in the Nth cycle, Wherein, when the current variation is zero or greater at least once in a charging cycle, the controller determines that an event occurs in the charging cycle so that the count is increased by 1, and The controller diagnoses a defect of the battery cell based on an accumulated count of a plurality of charging cycles.

7. The battery diagnostic device according to claim 6, It is characterized in that When the accumulated count exceeds a predetermined reference value, the controller diagnoses that the battery cell is defective.

8. The battery diagnostic device according to claim 6, It is characterized in that The controller diagnoses that the battery cell is defective when the event occurs continuously in the charging cycle and a cumulative count corresponding to the event that occurs continuously exceeds a predetermined reference value.

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