Battery diagnosis apparatus and battery diagnosis method

Abstract

A battery diagnosis apparatus and a battery diagnosis method are disclosed. The battery diagnosis apparatus comprises: a sensing unit for measuring a voltage of a battery cell; and a control circuit for determining a voltage drop amount of the battery cell for each idle period on the basis of a voltage measurement signal collected at least twice from the sensing unit for each idle period. The control circuit is configured to generate self-discharge history data indicating a change in the voltage drop amount in a plurality of idle periods. The control circuit is configured to diagnose a self-discharge state of the battery cell on the basis of the self-discharge history data.

Description

Battery diagnostic device and battery diagnostic method

[0001] The present invention relates to a technology for diagnosing the self-discharge state of a battery.

[0002] This application claims priority to Korean Patent Application No. 10-2024-0011568, filed on January 25, 2024, and all contents disclosed in the specification and drawings of that application are incorporated herein by reference.

[0003]

[0004] Recently, as the demand for portable electronic products such as laptops, video cameras, and mobile phones has rapidly increased, and the development of electric vehicles, energy storage batteries, robots, and satellites has been in full swing, research into high-performance batteries capable of repeated charging and discharging is actively being conducted.

[0005] Currently commercialized batteries include nickel-cadmium batteries, nickel-hydrogen batteries, nickel-zinc batteries, and lithium batteries. Among these, lithium batteries are receiving attention for their advantages of being able to charge and discharge freely, having a very low self-discharge rate, and having a high energy density, as they have almost no memory effect compared to nickel-based batteries.

[0006] Battery systems requiring high voltage and / or large capacity, such as electric vehicles, typically include multiple batteries connected in series, parallel, or a series-parallel combination.

[0007] In a battery system, failure of a few batteries can have a significant negative impact on the overall performance and safety of the system. Therefore, it is crucial to properly detect individual battery failures when operating a battery system.

[0008] Among the various failure types of batteries, self-discharge failure is dependent on the battery's self-discharge factor. The self-discharge factor can be the amount of voltage drop, the rate of voltage drop, or a combination thereof.

[0009] Conventionally, a method has been adopted in which the battery voltage is measured at least twice while the battery is at rest, and based on the measured voltage values, it is determined whether a self-discharge failure exists in the battery.

[0010] However, the conventional method described above has limitations in that it determines faults solely based on the voltage drop during a single pause, resulting in a low level of accuracy. For example, if there is a temporary error in the voltage measurement process or external noise is mixed in, inaccurate voltage values ​​can be obtained, and diagnostic results for self-discharge faults based on such voltage values ​​are bound to be unreliable.

[0011]

[0012] The present invention has been devised to solve the above-mentioned problems, and the purpose of the present invention is to provide a device and method for diagnosing the self-discharge state of a battery cell by analyzing a change in the voltage drop of a battery cell based on the voltage of the battery cell measured in a plurality of idle periods sequentially provided by periodically or aperiodically stopping the charging and discharging of the battery cell.

[0013] Other objects and advantages of the present invention can be understood through the following description and will be more clearly understood through the embodiments of the present invention. Furthermore, it will be readily apparent that the objects and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims.

[0014]

[0015] A battery diagnostic device according to one aspect of the present invention includes a sensing unit for measuring the voltage of a battery cell, and a control circuit for determining a voltage drop of the battery cell for each idle period based on voltage measurement signals collected at least twice from the sensing unit for each idle period. The control circuit is configured to generate self-discharge history data indicating changes in the voltage drop amount for a plurality of idle periods. The control circuit is configured to diagnose a self-discharge state of the battery cell based on the self-discharge history data.

[0016] The control circuit may be configured to determine a first risk level due to an increasing trend in the voltage drop amount when an increasing trend is identified from the self-discharge history data.

[0017] The control circuit may be configured to determine the first risk level based on the intensity of the increasing trend. The control circuit may generate alarm information to warn of the first risk level.

[0018] The control circuit may be configured to determine a second risk level due to a decreasing trend in the voltage drop amount when a decreasing trend is identified from the self-discharge history data.

[0019] The control circuit may be configured to determine the second risk level based on the intensity of the decreasing trend. The control circuit may be configured to generate alarm information to warn of the second risk level.

[0020] The control circuit may be configured to perform a protective operation for the battery cell based on the results of the diagnosis of the self-discharge state.

[0021] The above protection operation may include at least one of a first operation for limiting allowable charge / discharge conditions including at least one of a temperature range, a SOC range, a voltage range, a maximum charge current, and a maximum discharge current for the battery cell, a second operation for determining a recommended timing of a next idle period to be applied to the battery cell, and a third operation for outputting a diagnostic message indicating a result of the diagnostic.

[0022] A battery pack according to another aspect of the present invention includes the battery diagnostic device.

[0023] A battery system according to another aspect of the present invention includes the battery diagnostic device.

[0024] A battery diagnosis method according to another aspect of the present invention includes a step of determining a voltage drop of a battery cell for each idle period based on voltage measurement signals collected at least twice for each idle period, a step of generating self-discharge history data indicating a change in the voltage drop amount in a plurality of idle periods, and a step of diagnosing a self-discharge state of the battery cell based on the self-discharge history data.

[0025] The step of diagnosing the self-discharge state of the battery cell may include a step of determining a first risk level due to the increasing trend in the voltage drop amount when the increasing trend is identified from the self-discharge history data.

[0026] The step of diagnosing the self-discharge state of the battery cell may include a step of determining a second risk level due to the decreasing trend when a decreasing trend of the voltage drop is identified from the self-discharge history data.

[0027] The above battery diagnosis method may further include a step of executing a protection operation for the battery cell based on the result of the diagnosis of the self-discharge state.

[0028] The above protection operation may include at least one of a first operation for limiting allowable charge / discharge conditions including at least one of a temperature range, a SOC range, a voltage range, a maximum charge current, and a maximum discharge current for the battery cell, a second operation for determining a recommended timing of a next idle period to be applied to the battery cell, and a third operation for outputting a diagnostic message indicating a result of the diagnostic.

[0029]

[0030] According to at least one of the embodiments of the present invention, the self-discharge state of a battery cell can be diagnosed by analyzing self-discharge history data representing a change in the voltage drop of a battery cell over a plurality of idle periods sequentially imposed by periodically or aperiodically stopping charging and discharging of the battery cell.

[0031] In addition, according to at least one of the embodiments of the present invention, at least one of an increasing trend that mainly appears when an internal short circuit condition of a battery cell worsens and a decreasing trend that mainly appears when byproducts of the battery cell excessively accumulate can be identified from self-discharge history data, and a differentiated protection operation can be performed on the battery cell depending on which of the increasing trend and decreasing trend is identified.

[0032] The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

[0033]

[0034] The following drawings attached to this specification illustrate preferred embodiments of the present invention, and together with the detailed description of the invention described below, serve to further understand the technical idea of ​​the present invention, and therefore, the present invention should not be interpreted as being limited to matters described in such drawings.

[0035] FIG. 1 is a drawing exemplarily showing the configuration of a battery system including a battery diagnostic device according to the present invention.

[0036] Figures 2 and 3 are drawings for reference in explaining the self-discharge phenomenon of a battery cell.

[0037] Figure 4 is a drawing for reference in explaining an example of a temporal change in the self-discharge state of a battery cell.

[0038] FIG. 5 is a drawing for reference in explaining another example of temporal changes in the self-discharge state of a battery cell.

[0039] Figure 6 is a flowchart schematically illustrating a battery diagnosis method according to the present invention.

[0040] FIG. 7 is an exemplary flowchart for explaining the sub-steps of step S630 included in the method of FIG. 6.

[0041] FIG. 8 is an exemplary flowchart for explaining the sub-steps of step S640 included in the method of FIG. 6.

[0042]

[0043] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Prior to this, it should be noted that the terms and words used in this specification and claims should not be construed as limited to their conventional or dictionary meanings. Based on the principle that the inventor can appropriately define the concepts of terms to best explain his or her invention, they should be interpreted in a way that conforms to the technical spirit of the present invention.

[0044] Accordingly, the embodiments described in this specification and the configurations illustrated in the drawings are merely the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention. Therefore, it should be understood that there may be various equivalents and modified examples that can replace them at the time of filing this application.

[0045] Terms that include ordinal numbers, such as first, second, etc., are used to distinguish one of the various components from the rest, and are not used to limit the components by such terms.

[0046] Throughout the specification, when a part is said to "include" a component, this does not exclude other components, unless otherwise stated, but rather implies that other components may be included. Furthermore, terms such as "unit" used throughout the specification mean a unit that processes at least one function or operation, and may be implemented using hardware, software, or a combination of hardware and software.

[0047] Additionally, throughout the specification, when we say that a part is "connected" to another part, this includes not only cases where it is "directly connected" but also cases where it is "indirectly connected" with other elements in between.

[0048] FIG. 1 is a drawing exemplarily showing the configuration of a battery system including a battery diagnostic device according to the present invention.

[0049] Referring to Fig. 1, a battery system (1) includes a system controller (2), a battery pack (10), a relay (20), and a power load (30). The charge / discharge terminals (P+, P-) of the battery pack (10) can be electrically coupled to a charger (3) via a charging cable or the like. The type of the battery system (1) is not particularly limited as long as it is an electric system in which a battery (11) is mounted as a power source, such as an electric vehicle, or has the purpose of controlling and / or managing the state of the battery (11) from the outside, such as a charging station.

[0050] The system controller (2) (e.g., ECU: Electronic Control Unit) may be configured to transmit a key-on signal to the battery diagnostic device (100) in response to an operation button (not shown) provided in the battery system (1) being turned to the ON position by a user. The system controller (2) may be configured to transmit a key-off signal to the battery diagnostic device (100) in response to an operation button being turned to the OFF position by a user. The charger (3) may communicate with the system controller (2) and supply charging power selected from among constant power, constant current, and constant voltage through the charge / discharge terminals (P+, P-) of the battery pack (10).

[0051] The charge / discharge terminals (P+, P-) of the battery pack (10) can be electrically connected to an electric load (30) and / or a charger (3) via a power cable or the like. The charger (3) may be included in the battery system (1) or may be provided externally to the battery system (1) so as to be detachably attached to the battery pack (10).

[0052] The battery pack (10) includes a battery (11). The battery (11) includes at least one battery cell (BC). In Fig. 1, the battery (11) includes a plurality of battery cells (BC1 to BC) connected in series. N , N is a natural number greater than or equal to 2) is illustrated as an example. Multiple battery cells (BC1 to BC N ) may be provided to have identical electrochemical specifications.

[0053] Hereinafter, in explaining the common content of multiple battery cells (BC1 to BCN), the symbol 'BC' is assigned to the battery cells. The charger (3) can perform the charge / discharge cycle required to diagnose the battery cell (BC) through collaboration with an inverter (31) having a discharge function.

[0054] A battery cell (BC) includes a positive electrode and a negative electrode. It may include at least one unit cell as an electrochemical device capable of repeated charging and discharging. The battery cell (BC) is a target of diagnosis by a battery diagnosis device (100).

[0055] The relay (20) is electrically connected in series to the battery (11) via a power path connecting the battery (11) and the inverter (31). In Fig. 1, the relay (20) is illustrated as being connected between the positive terminal of the battery (11) and the charge / discharge terminal (P+). The relay (20) is turned on and off in response to a switching signal from the battery diagnostic device (100). The relay (20) may be a mechanical contactor that is turned on and off by the magnetic force of a coil, or a semiconductor switch such as a MOSFET (Metal Oxide Semiconductor Field Effect transistor).

[0056] The electric load (30) includes an inverter (31) and may further include an electric motor (32).

[0057] An inverter (31) is provided to convert direct current power from a battery (11) included in a battery pack (10) into alternating current power and / or direct current power of a different voltage level in response to a command from a battery diagnostic device (100) or a system controller (2).

[0058] The electric motor (32) is driven using AC power and / or DC power supplied from the inverter (31). For example, a three-phase AC motor can be used as the electric motor (32). The electric load (30) may collectively refer to components within the battery system (1) that require discharge power from the battery (11), including the inverter (31) and the electric motor (32).

[0059] A battery diagnostic device (100) may be included in a battery pack (10). The battery diagnostic device (100) includes a sensing unit (110) and a control circuit (130). The battery diagnostic device (100) may further include a communication circuit (150).

[0060] The sensing unit (110) includes a voltage sensor (111). The sensing unit (110) may further include at least one of a current sensor (112) and a temperature sensor (113). The voltage sensor (111), the current sensor (112), and the temperature sensor (113) may individually generate a voltage measurement signal, a current measurement signal, and a temperature measurement signal, which will be described later.

[0061] A voltage sensor (111) is connected to the positive and negative terminals of a battery cell (BC), and is configured to detect a voltage between both ends of the battery cell (BC) (which may be referred to as a 'full cell voltage') and generate a voltage measurement signal representing a detected value of the detected voltage. The voltage sensor (111) may be implemented as one or a combination of two or more of known voltage detection elements, such as a voltage measurement IC.

[0062] The current sensor (112) can be connected in series to the battery (11) through a current path between the battery (11) and the inverter (31). The current sensor (112) is configured to detect a current flowing through the battery (11) (which may be referred to as a 'charge / discharge current') and generate a current measurement signal representing the detected current. A plurality of battery cells (BC1 to BC) N ) are connected in series, the current flowing in the battery (11) is the same as the current flowing in the individual battery cells (BC). The current sensor (112) can be implemented as one or a combination of two or more of known current detection elements such as a shunt resistor, a Hall effect element, etc.

[0063] The temperature sensor (113) is attached to the outer surface of the battery cell (BC) or installed at a point close to the battery cell (BC), and is configured to detect the temperature of the battery cell (BC) and generate a temperature measurement signal representing the detected temperature as a detection value. The temperature sensor (113) may be implemented as one or a combination of two or more of known temperature detection elements such as a thermocouple, a thermistor, a bimetal, etc.

[0064] The communication circuit (150) is configured to support wired or wireless communication between the control circuit (130) and the system controller (2). The wired communication may be, for example, CAN (control area network) communication, and the wireless communication may be, for example, Zigbee or Bluetooth communication. Of course, as long as it supports wired or wireless communication between the control circuit (130) and the system controller (2), the type of communication protocol is not particularly limited. The communication circuit (150) may include an output device (e.g., a display, a speaker) that provides information received from the control circuit (130) and / or the system controller (2) in a form recognizable to a user (driver).

[0065] The control circuit (130) is operably coupled to a relay (20), a voltage sensor (111), and a communication circuit (150). The fact that the two components are operably coupled means that the two components are directly or indirectly connected so as to be capable of transmitting and receiving signals in one or both directions.

[0066] The control circuit (130) can collect a voltage measurement signal from the voltage sensor (111), a current measurement signal from the current sensor (112), and / or a temperature measurement signal from the temperature sensor (113). The control circuit (130) can convert and record each analog signal collected from the sensors (111, 112, 113) into a digital value using an ADC (Analog to Digital Converter) provided therein. Alternatively, at least one of the voltage sensor (111), the current sensor (112), and the temperature sensor (113) can include an ADC therein and transmit a digital value output by the ADC to the control circuit (130).

[0067] The control circuit (130) may be referred to as a 'battery controller' and may be implemented in hardware using at least one of application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), microprocessors, and other electrical units for performing functions.

[0068] The memory (131) may include at least one type of storage medium among, for example, a flash memory type, a hard disk type, an SSD (Solid State Disk type), an SDD (Silicon Disk Drive type), a multimedia card micro type, a random access memory (RAM), a static random access memory (SRAM), a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), and a programmable read-only memory (PROM). The memory (131) may store data and a program required for an operation by the control circuit (130). The memory (131) may store data indicating a result of an operation by the control circuit (130).

[0069] When the relay (20) is turned on, the battery (11) enters the charging mode or the discharging mode. When the relay (20) is turned off while the battery (11) is in use in the charging mode or the discharging mode, the battery (11) switches to the idle mode. In the present specification, the idle period may refer to the period during which the battery (11) is in the idle mode.

[0070] The control circuit (130) can turn on the relay (20) in response to a key-on signal. The control circuit (130) can turn off the relay (20) in response to a key-off signal. The key-on signal is a signal requesting a transition from idle to charging or discharging. The key-off signal is a signal requesting a transition from charging or discharging to idle. Alternatively, the on / off control of the relay (20) may be handled by the system controller (2) instead of the control circuit (130).

[0071] In this specification, measurement information of a parameter (e.g., time series data) may represent a temporal change history of the parameter over an arbitrary or specific period. In addition, a profile (or curve) representing a correspondence between two parameters obtained at regular timings during the same period may be a mapping of two measurement information of two parameters so that it can be plotted in the form of a two-dimensional graph, or a polynomial equation obtained by applying a predetermined curve fitting logic to a set of two mapped measurement information. Here, the degree of the highest term of the polynomial equation may be predetermined.

[0072] Figures 2 and 3 are diagrams used to illustrate the self-discharge phenomenon of a battery cell. Specifically, Figure 2 is a graph illustrating the temporal change in voltage of a battery cell due to the transition from charging to resting, and Figure 3 is a schematic diagram of an exemplary equivalent circuit model of a battery cell.

[0073] First, referring to Figure 2, t0 represents the transition timing from charging to resting. In other words, time point t0 can represent the start of the resting period. Accordingly, in the period prior to time point t0, the voltage of the battery cell (BC) increases due to charging, but from time point t0, the voltage of the battery cell (BC) gradually decreases.

[0074] The time point t0 may be the timing at which the voltage of the battery cell (BC) reaches a predetermined reference voltage. Specifically, the control circuit (130) may transmit a charging progress request to the charger (3) if the voltage of the battery cell (BC) is lower than the reference voltage, and then transmit a charging stop request to the charger (3) if the voltage of the battery cell (BC) reaches the reference voltage while the battery cell (BC) is being charged.

[0075] Ideally, during rest, the voltage of a battery cell (BC) should only drop to a specific Open Circuit Voltage (OCV) corresponding to its State of Charge (SOC) at time t0. However, if a self-discharge fault exists in the battery cell (BC), the voltage of the battery cell (BC) may fall below the specific OCV even during rest due to the small current flowing within the battery cell (BC).

[0076] The control circuit (130) can measure the voltage of the battery cell (BC) at least twice in each idle period and determine the voltage drop amount for each idle period based on the measured voltage values. In Fig. 2, t1 is exemplified as indicating the first voltage measurement timing in any idle period, and t2 is exemplified as indicating the second voltage measurement timing in the same idle period. For example, the voltage value (OCV) measured at time point t1 t1 ) and the voltage value measured at time point t2 (OCV t2 ) can be recorded in the memory (131) by the control circuit (130) as the voltage drop amount in the corresponding rest period. The term 'voltage drop amount' described in this specification may also be referred to as 'self-discharge amount'.

[0077] Time point t1 may be a point in time after a stabilization period has elapsed from time point t0. The stabilization period may be predetermined to allow sufficient time for the sudden change in voltage of the battery cell (BC) resulting from the transition from charging to resting to subside.

[0078] Time point t2 may be a waiting time elapsed from time point t1. The waiting time may be predetermined to determine the voltage drop required to diagnose a self-discharge condition. For example, the stabilization time may be one hour, and the waiting time may be one day.

[0079] Next, referring to Figure 3, the equivalent circuit model of the battery cell (BC) is a DC voltage source (V DC), may include a series circuit of an internal resistance component (R0) and an RC pair (R1, C). The RC pair (R1, C) may be a parallel circuit of a resistance component (R1) and a capacitance component (C). If a self-discharge fault exists, the equivalent circuit model may include an additional resistance component (R ISC ) will be included. Additional resistance component (R ISC ) is the leakage current (I) that causes voltage drop due to internal short circuit. ISC ) acts as a path for the internal short circuit. As the degree of internal short circuit worsens, additional resistance component (R ISC ) the resistance value decreases, and the leakage current (I ISC ) may increase, resulting in an increase in voltage drop.

[0080] FIG. 4 is a drawing for reference in explaining an example of a change in the self-discharge state of a battery cell over time, and FIG. 5 is a drawing for reference in explaining another example of a change in the self-discharge state of a battery cell over time.

[0081] The graph illustrated in Fig. 4 shows the change history of the voltage drop amount according to the repetition of the first charge / discharge cycle, and the graph illustrated in Fig. 5 shows the change history of the voltage drop amount according to the repetition of the second charge / discharge cycle. More specifically, Fig. 4 is a two-dimensional graph plotting exemplary self-discharge history data showing the change in the voltage drop amount according to the repetition of the first charge / discharge cycle. In the graph of Fig. 4, only an increasing trend in which the voltage drop amount continuously increases as the cycle count increases is confirmed. For reference, Figs. 4 and 5 may be obtained from the results of preliminary experiments on test battery cell(s) manufactured to have the same specifications as the battery cell (BC).

[0082] In the graphs of FIGS. 4 and 5, the X-axis represents the cycle count and the Y-axis represents the voltage drop.

[0083] The first charge-discharge cycle may include a procedure of charging and discharging the battery cell (BC) once between the upper and lower limits of the first voltage range (e.g., 2.5 to 3.7 V) in an environment where the external conditions are controlled to a first reference temperature (e.g., 25°C).

[0084] The second charge / discharge cycle may include a procedure of charging and discharging the battery cell (BC) once each between the upper and lower limits of the second voltage range (e.g., 2.5 to 4.2 V) in an environment where the external conditions are controlled to a second reference temperature (e.g., 50°C) higher than the first reference temperature. In other words, the second charge / discharge cycle can be said to be a harsher charge / discharge procedure than the first charge / discharge cycle in that a higher voltage and higher temperature charge / discharge environment is created by the second charge / discharge cycle compared to the first charge / discharge cycle.

[0085] Each charge / discharge cycle may include a charging procedure, a first pause procedure, a discharging procedure, and a second pause procedure, which are performed sequentially. A voltage regulation procedure may be added between the charging procedure and the first pause procedure of each charge / discharge cycle. The voltage regulation procedure may include applying a constant voltage to match the open circuit voltage of the battery cell (BC) to a reference voltage.

[0086] The charging procedure of each of the first and second charge / discharge cycles may be performed according to a CC (Constant Current)-CV (Constant Voltage) charging protocol. A first current rate may be used for the CC charging of the first charge / discharge cycle, and a second current rate may be used for the CC charging of the second charge / discharge cycle. The second current rate may be equal to or greater than the first current rate. The charging procedure of each of the first and second charge / discharge cycles may be performed according to a CC (Constant Current)-CV (Constant Voltage) charging protocol. A third current rate may be used for the discharging procedure of the first charge / discharge cycle, and a fourth current rate may be used for the discharging procedure of the second charge / discharge cycle. The fourth current rate may be equal to or greater than the third current rate.

[0087] Each time a charge / discharge cycle is completed, the cycle count may be increased by 1. The idle period may refer to a period during which both charging and discharging of the battery cell (BC) are stopped by the first idle procedure of the charge / discharge cycle. The control circuit (130) may determine the amount of voltage drop for each idle period. For reference, the second idle procedure is intended to resolve polarization caused by the discharge procedure of the charge / discharge cycle in the same cycle number, and charging and discharging of the battery cell (BC) are stopped for a predetermined period of time before performing the charging procedure of the next charge / discharge cycle.

[0088] Fig. 5 is a two-dimensional graph plotting exemplary self-discharge history data showing changes in voltage drop due to repetition of a second charge / discharge cycle. The front part of the graph of Fig. 5 is similar to the graph of Fig. 4 in that the voltage drop shows an increasing trend, whereas the graph of Fig. 5 differs from the graph of Fig. 4 in that the voltage drop changes from an increasing trend to a decreasing trend during the increase in the cycle count. In Fig. 5, the symbol K indicates the cycle count at which the change pattern of the voltage drop changes from an increasing trend to a decreasing trend.

[0089] Note that the timing at which the transition from an increasing trend to a decreasing trend occurs may depend on the history of usage conditions (e.g., charge / discharge current, charge / discharge voltage, temperature, and main usage SOC range) that change irregularly over the life of the battery cell (BC).

[0090] The inventor of the present invention discovered, during numerous experiments, a phenomenon in which, as the battery cell (BC) deteriorates during the beginning of its life (BOL), the voltage drop in the resting period gradually increases, but at a certain point, the increase in the voltage drop stops, and from the middle of its life (MOL), the voltage drop tends to decrease.

[0091] Specifically, in the early stage of use, the micro current paths generated inside the battery cell (BC) may increase, which may cause an increase in the voltage drop as illustrated in Fig. 4. On the other hand, as the battery cell (BC) is subjected to harsh conditions and further deteriorates and enters the mid-stage of use, it is presumed that by-products (e.g., lithium metal precipitates) accumulated on the electrode surface due to side reactions, etc., interfere with the current flow through the micro current paths between the positive and negative electrodes, resulting in a decrease in the speed of self-discharge as illustrated in Fig. 5.

[0092] Additionally, the inventors of the present invention have recognized, through numerous experimental results, that a significant increase in the amount of gas generated within a battery cell (BC) occurs when a transition event occurs from an increasing trend to a decreasing trend. Therefore, to ensure the safety and extend the life of a battery cell (BC), it is necessary to change the control strategy for the battery cell (BC) based on whether an increasing trend or a decreasing trend is identified from self-discharge history data.

[0093] Fig. 6 is a flowchart schematically illustrating a battery diagnosis method according to the present invention. The method of Fig. 6 can be repeatedly executed periodically.

[0094] Referring to FIGS. 1 to 6, in step S600, the control circuit (130) can determine whether the idle period of the battery cell (BC) has been initiated. If the value of step S600 is "Yes," the method of FIG. 6 can proceed to step S610. If the value of step S600 is "No," step S610 can be re-executed or the method of FIG. 6 can be terminated.

[0095] In step S610, the control circuit (130) can determine the voltage drop of the battery cell (BC) based on the voltage measurement signal collected at least twice from the sensing unit (110) during the idle period.

[0096] In step S620, the control circuit (130) can generate self-discharge history data indicating changes in voltage drop amounts in multiple rest periods.

[0097] In detail, when the voltage drop amount determined in step S610 is at the Mth (M is a natural number greater than or equal to 2) rest period, the self-discharge history data generated in step S620 may be the M voltage drops sorted in the chronological order in which they were each determined. For example, before step S610 is performed, the self-discharge history data may include the first to M-1th voltage drops, and when the Mth voltage drop amount is determined by step S610, the self-discharge history data may be updated in step S620 so that the Mth voltage drop amount is added. By the update function in step S620, the self-discharge history data may include the first to Mth voltage drops sorted in chronological order.

[0098] In step S630, the control circuit (130) diagnoses the self-discharge status of the battery cell (BC) based on self-discharge history data. The specific procedure of step S630 will be described in more detail later with reference to FIG. 7.

[0099] In step S640, the control circuit (130) executes a protection procedure for the battery cell (BC) based on the results of the diagnosis performed in step S640. Step S640 is not mandatory and may be omitted from the method of FIG. 6 as needed. The specific procedure of step S640 will be described in more detail later with reference to FIG. 8.

[0100] FIG. 7 is an exemplary flowchart for explaining the sub-steps of step S630 included in the method of FIG. 6.

[0101] Referring to FIG. 7, in step S710, the control circuit (130) can identify, from the self-discharge history data, a change pattern of the voltage drop amount over multiple rest periods as either an increasing trend or a decreasing trend.

[0102] For example, if the current voltage drop (M voltage drop) is greater than the previous voltage drop (M-1 voltage drop), the change pattern can be identified as an increasing trend, otherwise the change pattern can be identified as a decreasing trend.

[0103] As another example, if M is greater than u (which may be a predetermined value as a natural number greater than or equal to 2), the control circuit (130) may determine an approximate straight line by applying the least squares method to data points representing the Mu voltage drop amount to the M voltage drop amount. If the slope of the approximate straight line is positive, the change pattern may be identified as an increasing trend, and otherwise, the change pattern may be identified as a decreasing trend.

[0104] For reference, considering that there is a characteristic that an increasing trend usually precedes a decreasing trend, the control circuit (130) can perform an identification operation to determine whether a decreasing trend exists in the self-discharge history data, on the condition that a history of previously identifying an increasing trend is confirmed.

[0105] In step S720, the control circuit (130) can determine whether an increasing trend was identified in step S710. If the value of step S720 is "Yes," the process can proceed to step S730. If the value of step S720 is "No," this means that a decreasing trend was identified in step S710, in which case the process can proceed to step S740.

[0106] In step S730, the control circuit (130) may determine a first risk level due to the increasing trend. The first risk level may be a type of diagnostic parameter indicating the likelihood or severity level of an internal short circuit as described above with reference to FIG. 3.

[0107] The control circuit (130) can determine the first risk level based on the intensity of the increasing trend. As the intensity of the increasing trend, the difference between the current voltage drop (the Mth voltage drop) and the previous voltage drop (the M-1th voltage drop) and / or the absolute value of the slope of the approximate straight line can be used.

[0108] In step S740, the control circuit (130) may determine a second risk level due to the decreasing trend. The second risk level may be a type of diagnostic parameter indicating the likelihood or severity of gas overproduction as described above with reference to FIG. 5.

[0109] The control circuit (130) can determine the second risk level based on the intensity of the decreasing trend. As the intensity of the decreasing trend, the difference between the current voltage drop (the Mth voltage drop) and the previous voltage drop (the M-1th voltage drop) and / or the absolute value of the slope of the approximate straight line can be used.

[0110] FIG. 8 is an exemplary flowchart for explaining the sub-steps of step S640 included in the method of FIG. 6.

[0111] Referring to FIG. 8, in step S810, the control circuit (130) may execute a first operation to limit allowable charge / discharge conditions including at least one of a temperature range, an SOC range, a voltage range, a maximum charge current, and a maximum discharge current for the battery cell (BC) based on the diagnosis result for the self-discharge state of the battery cell (BC).

[0112] The first relationship data between the limit amount of the allowable charge / discharge condition and the first risk level and the second relationship data between the limit amount of the allowable charge / discharge condition and the second risk level may be recorded in advance in the memory (131).

[0113] The control circuit (130) can execute the first operation by referring to the first relationship data when an increasing trend is identified, and can execute the first operation by referring to the second relationship data when a decreasing trend is identified.

[0114] For example, as the second risk level increases, the upper limit of at least one of the temperature range, SOC range, and voltage range allowed for the battery cell (BC) may be set lower. Specifically, if the upper temperature limit is lowered by the first action executed in response to the identification of a decreasing trend, the rate of gas generation can be slowed, significantly reducing the risk of fire or explosion.

[0115] A decreasing trend is a strong indication of excessive gas generation within the battery cell (BC), and since a large amount of gas accumulated within the battery cell (BC) can easily lead to an explosion of the battery cell (BC), a decreasing trend can be said to indicate a higher level of risk than an increasing trend. Therefore, when the intensity of the decreasing trend and the increasing trend are equal, the limit of the allowable charge / discharge conditions according to the second relationship data can be set to be a certain value greater than the limit of the allowable charge / discharge conditions according to the first relationship data.

[0116] In step S820, the control circuit (130) may execute a second operation for determining a recommended timing for the next idle period to be applied to the battery cell (BC). The third relationship data between the allowable period and the first risk level and the fourth relationship data between the allowable period and the second risk level may be pre-recorded in the memory (131).

[0117] If an increasing trend is identified, the control circuit (130) may determine the allowable period by referring to the third relationship data, and if a decreasing trend is identified, the allowable period by referring to the fourth relationship data. Then, the control circuit (130) may determine the point in time after the allowable period has elapsed from the current point in time as the recommended time for the next rest period. For example, the higher the second risk level, the earlier the recommended time for the next rest period may be.

[0118] When the recommended time arrives, the user of the battery system (1) may be encouraged to allow a rest period for re-diagnosis of the self-discharge state.

[0119] In step S830, the control circuit (130) may execute a third operation that outputs a diagnostic message indicating the results of a diagnosis of the self-discharge state of the battery cell (BC). The diagnostic message may include information indicating at least one of the charging / discharging conditions limited by the first operation and the recommended time determined by the second operation. The diagnostic message may include alarm information for notifying the first risk level or the second risk level.

[0120] The diagnostic message can be transmitted from the control circuit (130) to the system controller (2) via the communication circuit (150). The system controller (2) can control an information output device (not shown) provided in the battery system (1) to visually and / or audibly output information contained in the diagnostic message to the user.

[0121] Any one or both of steps S810, S820, and S830 may be omitted from the method of FIG. 8. Furthermore, the execution order between steps S810, S820, and S830 is not limited to the example of FIG. 8. For example, step S810 may be executed after step S820 is executed. As another example, if steps S810 and S820 are omitted from the method of FIG. 8, step S830 may be executed immediately after step S630 ends.

[0122] The embodiments of the present invention described above are not implemented only through devices and methods, but may also be implemented through a program that realizes a function corresponding to the configuration of the embodiments of the present invention or a recording medium on which the program is recorded, and such implementation can be easily implemented by an expert in the technical field to which the present invention belongs based on the description of the embodiments described above.

[0123] Although the present invention has been described above with reference to limited embodiments and drawings, the present invention is not limited thereto, and it is obvious that various modifications and variations are possible within the scope of the technical idea of ​​the present invention and the equivalent scope of the patent claims to be described below by a person having ordinary skill in the art to which the present invention pertains.

[0124] In addition, the present invention described above is not limited to the above-described embodiments and the attached drawings, and all or part of each embodiment may be selectively combined and configured so that various modifications can be made, as those skilled in the art can make various substitutions, modifications, and changes within the scope of the technical idea of ​​the present invention.

Claims

1. A sensing unit that measures the voltage of a battery cell; and A control circuit for determining the voltage drop of the battery cell for each rest period based on a voltage measurement signal collected at least twice from the sensing unit for each rest period, The above control circuit, Generate self-discharge history data indicating changes in the voltage drop amount in multiple rest periods, A battery diagnostic device that diagnoses the self-discharge status of the battery cell based on the self-discharge history data.

2. In paragraph 1, The above control circuit, A battery diagnostic device configured to determine a first risk level due to the increasing trend when an increasing trend of the voltage drop is identified from the self-discharge history data.

3. In paragraph 2, The above control circuit, Depending on the intensity of the above increasing trend, the first risk level is determined, A battery diagnostic device that generates alarm information for warning of the above first risk level.

4. In paragraph 1, The above control circuit, A battery diagnostic device configured to determine a second risk level due to the decreasing trend when a decreasing trend of the voltage drop is identified from the self-discharge history data.

5. In paragraph 4, The above control circuit, Depending on the intensity of the above-mentioned decreasing trend, the second risk level is determined, A battery diagnostic device that generates alarm information to warn of the second risk level.

6. In paragraph 1, The above control circuit, A battery diagnostic device that executes a protective action for the battery cell based on the results of the diagnosis of the self-discharge state.

7. In paragraph 6, The above protective action is, A first operation for limiting allowable charge / discharge conditions including at least one of a temperature range, a SOC range, a voltage range, a maximum charge current, and a maximum discharge current for the battery cell; A second operation for determining a recommended timing for the next rest period to be granted to the battery cell; and A third action for outputting a diagnostic message indicating the result of the above diagnosis; A battery diagnostic device comprising at least one of:

8. A battery pack comprising a battery diagnostic device according to any one of claims 1 to 7.

9. A battery system comprising a battery diagnostic device according to any one of claims 1 to 7.

10. A step of determining the voltage drop of a battery cell for each rest period based on voltage measurement signals collected at least twice for each rest period; A step of generating self-discharge history data indicating changes in the voltage drop amount in multiple rest periods; and A battery diagnosis method, comprising a step of diagnosing a self-discharge state of the battery cell based on the self-discharge history data.

11. In paragraph 10, The step of diagnosing the self-discharge status of the above battery cell is: When an increasing trend of the voltage drop is identified from the self-discharge history data, a step of determining a first risk level due to the increasing trend; A battery diagnostic method comprising:

12. In paragraph 10, The step of diagnosing the self-discharge status of the above battery cell is: When a decreasing trend of the voltage drop is identified from the self-discharge history data, a step of determining a second risk level due to the decreasing trend; A battery diagnostic method comprising:

13. In paragraph 10, A battery diagnosis method further comprising a step of executing a protective action for the battery cell based on the results of the diagnosis of the self-discharge state.

14. In paragraph 13, The above protective action is, A first operation for limiting allowable charge / discharge conditions including at least one of a temperature range, a SOC range, a voltage range, a maximum charge current, and a maximum discharge current for the battery cell; A second operation for determining a recommended timing for the next rest period to be granted to the battery cell; and A third action for outputting a diagnostic message indicating the result of the above diagnosis; A battery diagnostic method comprising at least one of:

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