Battery diagnosis device and battery diagnosis method

Abstract

The invention provides a battery diagnosis apparatus and a battery diagnosis method. The battery diagnosis apparatus includes: a sensing unit configured to measure a voltage of a battery cell; and a control circuit configured to determine an amount of voltage drop of the battery cell for each rest period based on the voltage measurement signals collected from the sensing unit at least twice at each rest period. The control circuit is configured to generate self-discharge history data indicative of a change in an amount of voltage drop in a plurality of rest periods. The control circuit is configured to diagnose a self-discharge state of the battery cell based on the self-discharge history data.

Description

Technical Field

[0001] This disclosure relates to self-discharge diagnosis in batteries.

[0002] This application is based on and claims priority to Korean Patent Application No. 10-2024-0011568, filed in Korea on January 25, 2024, the disclosure of which is incorporated herein by reference. Background Technology

[0003] In recent years, the demand for portable electronic products such as laptops, cameras and mobile phones has increased rapidly, and with the widespread development of electric vehicles, energy storage devices, robots and satellites, much research has been conducted on high-performance batteries that can be repeatedly charged and discharged.

[0004] Currently, commercially available batteries include nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, and lithium batteries. Among them, lithium batteries have a small or no memory effect, and therefore they have received more attention than nickel-based batteries because their advantages are that they can be recharged whenever convenient, have a very low self-discharge rate, and high energy density.

[0005] Battery systems that require high voltage and / or large capacity (such as electric vehicles) typically consist of multiple batteries connected in series, in parallel, or both.

[0006] In a battery system, a fault in any cell can adversely affect the performance and safety of the entire system. Therefore, correctly detecting faults in individual cells is crucial in battery system management.

[0007] Among many different types of battery failures, self-discharge failure depends on the battery's self-discharge factor. Here, the self-discharge factor can include the amount and rate of voltage drop, or a combination thereof.

[0008] Self-discharge faults in batteries are typically determined based on measuring the battery voltage two or more times during a rest period.

[0009] However, fault determination based on the amount of voltage drop during a single pause leads to low accuracy. For example, inaccurate voltage values ​​can be obtained when there are temporary errors or external noise during voltage measurement, and the diagnosis of self-discharge faults based on voltage values ​​has low reliability. Summary of the Invention

[0010] Technical issues

[0011] This disclosure is designed to solve the above-mentioned problems, and therefore aims to provide an apparatus and method for diagnosing the self-discharge state of a battery cell by analyzing the change in the amount of voltage drop of the battery cell based on the voltage of the battery cell measured in a plurality of rest periods sequentially allocated by periodically or non-periodically stopping the charging / discharging of the battery cell.

[0012] These and other objects and advantages of this disclosure will be understood from the following description and will become apparent from the embodiments of this disclosure. Moreover, it will be readily understood that the objects and advantages of this disclosure can be achieved by the means set forth in the appended claims and combinations thereof.

[0013] Technical solution

[0014] A battery diagnostic apparatus according to one aspect of this disclosure includes: a sensing unit configured to measure the voltage of a battery cell; and a control circuit configured to determine the amount of voltage drop of the battery cell during each rest period based on voltage measurement signals collected from the sensing unit at least twice during each rest period. The control circuit is configured to generate self-discharge history data indicating changes in the amount of voltage drop over multiple rest periods. The control circuit is configured to diagnose the self-discharge state of the battery cell based on the self-discharge history data.

[0015] The control circuit can be configured to determine the first risk level caused by the increasing trend of voltage drop when an increasing trend of voltage drop is identified from self-discharge history data.

[0016] The control circuit can be configured to determine a first risk level based on the strength of the increasing trend. The control circuit can also be configured to generate an alarm message to warn of the first risk level.

[0017] The control circuit can be configured to determine a second risk level caused by a decreasing trend in the amount of voltage drop when a decreasing trend is identified from the self-discharge history data.

[0018] The control circuit can be configured to determine a second risk level based on the strength of the decreasing trend. The control circuit can also be configured to generate an alarm message to warn of the second risk level.

[0019] The control circuit can be configured to perform protective operations on individual battery cells based on the results of diagnostic self-discharge status.

[0020] The protection operation may include at least one of a first operation, a second operation, and a third operation. The first operation is to limit the permissible charging / discharging conditions, which include at least one of the following: temperature range, state of charge (SOC) range, voltage range, maximum charging current, and maximum discharging current of the battery cell. The second operation is to determine the recommended timing for the next rest period to be allocated to the battery cell. The third operation is to output a diagnostic message indicating the results of the diagnostics.

[0021] According to another aspect of this disclosure, a battery pack includes a battery diagnostic device.

[0022] According to another aspect of the present invention, a battery system includes a battery diagnostic device.

[0023] A battery diagnostic method according to another aspect of this disclosure includes: determining the amount of voltage drop of a battery cell during each rest period based on voltage measurement signals collected at least twice during each rest period; generating self-discharge history data indicating changes in the amount of voltage drop during multiple rest periods; and diagnosing the self-discharge state of a battery cell based on the self-discharge history data.

[0024] Diagnosing the self-discharge status of a battery cell may include: when an increasing trend in the amount of voltage drop is identified from historical self-discharge data, determining the first level of risk caused by the increasing trend.

[0025] Diagnosing the self-discharge status of a battery cell can include determining a second risk level caused by a decreasing trend in the amount of voltage drop when a decreasing trend is identified from historical self-discharge data.

[0026] Battery diagnostic methods may also include performing protective operations on individual battery cells based on the results of diagnostic self-discharge status.

[0027] The protection operation may include at least one of a first operation, a second operation, and a third operation. The first operation is to limit the permissible charging / discharging conditions, which include at least one of the battery cell's temperature range, SOC range, voltage range, maximum charging current, and maximum discharging current. The second operation is to determine the recommended timing for the next rest period to be allocated to the battery cell. The third operation is to output a diagnostic message indicating the results of the diagnostics.

[0028] Beneficial effects

[0029] According to at least one embodiment of the present disclosure, the self-discharge state of a battery cell can be diagnosed by analyzing self-discharge history data indicating changes in the amount of voltage drop of the battery cell during multiple rest periods that are sequentially allocated by periodically or non-periodically stopping the charging / discharging of the battery cell.

[0030] In addition, according to at least one of the embodiments of this disclosure, at least one of an increasing trend found mainly in the case of severe internal short circuit in a battery cell and a decreasing trend found mainly in the case of excessive accumulation of by-products in a battery cell can be identified from the self-discharge history data, and differentiated protection operations for the battery cell can be performed depending on the identified trend among the increasing and decreasing trends.

[0031] The effects of this disclosure are not limited to those described above, and those skilled in the art will clearly understand these and other effects from the appended claims. Attached Figure Description

[0032] The accompanying drawings illustrate exemplary embodiments of the present disclosure and, together with the following detailed description, are intended to provide a better understanding of the technical aspects of the present disclosure; therefore, the present disclosure should not be construed as being limited to the drawings.

[0033] Figure 1 This is an exemplary diagram illustrating the architecture of a battery system including a battery diagnostic device according to the present disclosure.

[0034] Figure 2 and Figure 3 This diagram is used as a reference when describing the self-discharge of a single battery cell.

[0035] Figure 4 The figure is cited in an example describing the time-dependent changes in the self-discharge state of a single battery cell.

[0036] Figure 5 This figure is cited in another example describing the time-dependent changes in the self-discharge state of a single battery cell.

[0037] Figure 6 This is a schematic flowchart illustrating a battery diagnostic method according to the present disclosure.

[0038] Figure 7 The illustration includes Figure 6 An exemplary flowchart of a sub-step of step S630 in the method.

[0039] Figure 8 The illustration includes Figure 6 An exemplary flowchart of a sub-step of step S640 in the method. Detailed Implementation

[0040] In the following, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Before the description, it should be understood that the terms or words used in the specification and appended claims should not be construed as limited to their general and dictionary meanings, but should be interpreted based on the meanings and concepts corresponding to the technical aspects of the present disclosure, in a manner that allows the inventors to appropriately define the terms for best interpretation.

[0041] Therefore, the embodiments described herein and the illustrations shown in the accompanying drawings are exemplary embodiments of this disclosure to describe technical aspects of this disclosure, but are not intended to be limiting, and it should be understood that various other equivalents and modifications may be made thereto when this application is filed.

[0042] Ordinal terms such as “first” and “second” are used to distinguish one element from another among various elements, but are not intended to limit elements by terminology.

[0043] Unless the context clearly indicates otherwise, the terms "comprising" and "including" are used in this specification to specify the presence of the stated element, but do not exclude the presence or addition of one or more other elements. Additionally, the term "unit" as used herein refers to at least one processing unit that performs at least one function or operation and can be implemented individually or in combination by hardware and software.

[0044] Furthermore, as will be further understood throughout this specification, when an element is referred to as being “connected” to another element, it may be directly connected to the other element or there may be an intermediate element.

[0045] Figure 1 This is an exemplary diagram illustrating the architecture of a battery system including a battery diagnostic device according to the present disclosure.

[0046] refer to Figure 1 The battery system 1 includes a system controller 2, a battery pack 10, a relay 20, and an electrical load 30. The charging / discharging terminals P+ and P- of the battery pack 10 can be electrically coupled to the charger 3 via charging cables. The battery system 1 is not limited to a specific type and may include, for example, any electrical system that uses the battery 11 as a power source—such as an electric vehicle—or any electrical system designed to control and / or manage the state of the battery 11 from the outside—such as a charging station.

[0047] System controller 2 (e.g., electronic control unit (ECU)) can be configured to send a key-on signal to battery diagnostic device 100 in response to a user changing the operation button (not shown) of battery system 1 to the on position. System controller 2 can also be configured to send a key-off signal to battery diagnostic device 100 in response to a user changing the operation button to the off position. Charger 3 can supply charging power selected from constant power, constant current, and constant voltage through the charging / discharging terminals P+ and P- of battery pack 10 via communication with system controller 2.

[0048] The charging / discharging terminals P+ and P- of the battery pack 10 can be electrically coupled to the electrical load 30 and / or the charger 3 via power cables. The charger 3 can be included in the battery system 1 or can be located outside the battery system 1, such that the charger 3 can be attached to or removed from the battery pack 10.

[0049] Battery pack 10 includes battery 11. Battery 11 includes at least one battery cell BC. Figure 1 The diagram illustrates multiple battery cells BC1 to BC1 connected in series. N (N is a natural number of 2 or greater) 11 cells. Multiple cell BC1 to BC N They can be set with the same electrochemical specifications.

[0050] In the following text, multiple battery cells BC1 to BC are described. N In the common description, the symbol "BC" is attached to the battery cell. The charger 3 can perform the charge / discharge cycle required for diagnosing the battery cell BC by cooperating with the inverter 31, which has a discharge function.

[0051] A single battery cell BC includes a positive electrode and a negative electrode. A single battery cell BC may include at least one individual cell as an electrochemical device capable of being repeatedly charged and discharged. The single battery cell BC will be diagnosed by a battery diagnostic device 100.

[0052] Relay 20 is connected in series to battery 11 through a power path connecting battery 11 and inverter 31. Figure 1 A relay 20 is shown connected between the positive terminal of battery 11 and the charging / discharging terminal P+. Relay 20 is controlled to turn on / off in response to a switching signal from battery diagnostic device 100. Relay 20 may include a mechanical contactor that is magnetically switched on or off via a coil or a semiconductor switch, such as a metal-oxide-semiconductor field-effect transistor (MOSFET).

[0053] The electrical load 30 includes an inverter 31 and may also include a motor 32.

[0054] The inverter 31 is configured to convert direct current (DC) power from the battery 11 included in the battery pack 10 into alternating current (AC) power and / or DC power at different voltage levels in response to commands from the battery diagnostic device 100 or the system controller 2.

[0055] The motor 32 operates using AC and / or DC power supplied from the inverter 31. The motor 32 may include, for example, a three-phase AC motor. The electrical load 30 may collectively refer to the components in the battery system 1 that require the discharge power of the battery 11, including the inverter 31 and the motor 32.

[0056] The battery diagnostic device 100 may be included in the battery pack 10. The battery diagnostic device 100 includes a sensing unit 110 and a control circuit 130. The battery diagnostic device 100 may also include a communication circuit 150.

[0057] The sensing unit 110 includes a voltage sensor 111. The sensing unit 110 may also 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 can respectively generate a voltage measurement signal, a current measurement signal, and a temperature measurement signal as described below.

[0058] Voltage sensor 111 is connected to the positive and negative terminals of battery cell BC and is configured to detect the voltage across battery cell BC (referred to as the "total cell voltage") and generate a voltage measurement signal indicating the detected value of the voltage. Voltage sensor 111 may include one or a combination of known voltage detection devices such as a voltage measurement IC.

[0059] A current sensor 112 can be connected in series to the battery 11 via the current path between the battery 11 and the inverter 31. The current sensor 112 is configured to detect the current flowing through the battery 11 (referred to as the "charging / discharging current") and generate a current measurement signal indicating the detected value of the current. This is because multiple battery cells BC1 to BC2... N They are connected in series, so the current flowing in battery 11 is the same as the current flowing in a single battery cell BC. Current sensor 112 may include one or a combination of known current sensing devices such as a shunt resistor or a Hall effect device.

[0060] Temperature sensor 113 is attached to the outer surface of battery cell BC or mounted at a location near battery cell BC, and is configured to detect the temperature of battery cell BC and generate a temperature measurement signal indicating a detected value of the temperature. Temperature sensor 113 may include one or a combination of known temperature sensing devices such as thermocouples, thermistors, or bimetallic devices.

[0061] Communication circuit 150 is configured to support wired or wireless communication between control circuit 130 and system controller 2. Wired communication may include, for example, Controller Area Network (CAN) communication, and wireless communication may include, for example, Zigbee or Bluetooth communication. The communication protocol may include any type of communication protocol that supports wired / wireless communication between control circuit 130 and system controller 2, and is not limited to a specific communication protocol. Communication circuit 150 may include output devices (e.g., a display, a speaker) to provide information received from control circuit 130 and / or system controller 2 in a user-recognizable format.

[0062] The control circuit 130 can be operatively coupled to the relay 20, the voltage sensor 111, and the communication circuit 150. Here, "operatively coupled" means directly or indirectly connected to enable signal transmission and reception in one or both directions.

[0063] Control circuit 130 can collect voltage measurement signals from voltage sensor 111, current measurement signals from current sensor 112, and / or temperature measurement signals from temperature sensor 113. Control circuit 130 can convert and record each analog signal collected from sensors 111, 112, and 113 as a digital value using an analog-to-digital converter (ADC) provided therein. Alternatively, at least one of voltage sensor 111, current sensor 112, and temperature sensor 113 may include an ADC, and the digital value output from the ADC may be sent to control circuit 130.

[0064] The control circuit 130 may also be referred to as a "battery controller" and can be implemented in hardware using at least one of an application-specific integrated circuit (ASIC), a digital signal processor (DSP), a digital signal processing device (DSPD), a programmable logic device (PLD), a field-programmable gate array (FPGA), a microprocessor, and an electrical unit for performing other functions.

[0065] The memory 131 may include at least one type of storage medium, such as flash memory, hard disk, solid-state drive (SSD), silicon disk drive (SDD), multimedia card micro, random access memory (RAM), static random access memory (SRAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), or programmable read-only memory (PROM). The memory 131 may store data and programs required for the computational operations of the control circuit 130. The memory 131 may also store data indicating the results of the computational operations of the control circuit 130.

[0066] When relay 20 is turned on, battery 11 is in charging or discharging mode. When relay 20 is turned off and battery 11 is used in charging or discharging mode, battery 11 changes to rest mode. In this specification, rest period may refer to the time during which battery 11 is in rest mode.

[0067] Control circuit 130 can activate relay 20 in response to a key-on signal. Control circuit 130 can deactivate relay 20 in response to a key-off signal. The key-on signal is a signal requesting a change from idle to charging or discharging. The key-off signal is a signal requesting a change from charging or discharging to idle. Alternatively, instead of control circuit 130, system controller 2 can be responsible for controlling the activation and deactivation of relay 20.

[0068] In this specification, the measurement information of the parameters (e.g., time series data) can indicate the time-related change history of the parameters over a certain time period or a specific time period. Furthermore, the profile (or curve) indicating the correspondence between two parameters acquired at regular intervals within the same time period can be a plot obtained by mapping the two measurement information of the two parameters to a two-dimensional (2D) graph, or a polynomial equation obtained by applying predetermined curve fitting logic to the set of two mapped measurement information. Here, the degree of the highest-degree term of the polynomial equation can be preset.

[0069] Figure 2 and Figure 3 This diagram is used as a reference when describing the self-discharge of a single battery cell. Specifically, Figure 2 It is a graph showing the time-dependent change in voltage within a single battery cell from charging to decommissioning. Figure 3 This is a diagram illustrating an exemplary equivalent circuit model of a single battery cell.

[0070] First, refer to Figure 2 t0 represents the timing of the change from charging to rest. In other words, time t0 can represent the start time of the rest period. Therefore, in the range before time t0, the voltage of battery cell BC increases through charging, and from time t0 onwards, the voltage of battery cell BC gradually decreases.

[0071] Time t0 can be the timing when the voltage of battery cell BC reaches a predetermined reference voltage. Specifically, when the voltage of battery cell BC is lower than the reference voltage, the control circuit 130 can send a charging request to the charger 3, and when the voltage of battery cell BC reaches the reference voltage during the charging of battery cell BC, it can send a charging stop request to the charger 3.

[0072] Ideally, during a rest period, the voltage of a single battery cell BC drops only to the specific open-circuit voltage (OCV) corresponding to the state of charge (SOC) at time t0. However, when 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 a rest period due to the small amount of current flowing in the battery cell BC.

[0073] The control circuit 130 can measure the voltage of the battery cell BC at least twice and determine the amount of voltage drop during each rest period based on the voltage value measured during each rest period. Figure 2 In this context, t1 represents the first voltage measurement timing within the rest period, and t2 represents the second voltage measurement timing within the same rest period. For example, the voltage value OCV measured at time t1. t1 The voltage value OCV measured at time t2 t2The difference can be recorded by the control circuit 130 in the memory 131 as the amount of voltage drop during the corresponding rest period. The "amount of voltage drop" used in this article can also be referred to as the "amount of self-discharge".

[0074] Time t1 can be the time after the stabilization time starting from time t0. The stabilization time can be the preset time taken for the voltage of a single battery cell BC to fully stabilize after a rapid change from charging to rest.

[0075] Time t2 can be the time following the standby time from time t1. The standby time can be preset to determine the amount of voltage drop required to diagnose self-discharge. For example, the settling time can be 1 hour, and the standby time can be 1 day.

[0076] Subsequently, reference Figure 3 The equivalent circuit model of a single battery cell BC can include a DC voltage source V. DC The internal resistance component R0 and the RC pair R1 and C are connected in series. The RC pair R1 and C can also be a parallel circuit of the resistive component R1 and the capacitive component C. When a self-discharge fault exists, the equivalent circuit model includes an additional resistive component R connected between the two ends of the series circuit. ISC Additional resistor component R ISC The leakage current I used to induce the voltage drop caused by an internal short circuit ISC The path. As the severity of internal short circuits increases, the additional resistor component R... ISC The resistance value decreases and the leakage current I ISC An increase in voltage leads to an increase in voltage drop.

[0077] Figure 4 The graph is cited in an example describing the time-dependent changes in the self-discharge state of a single battery cell, and Figure 5 This figure is cited in another example describing the time-dependent changes in the self-discharge state of a single battery cell.

[0078] Figure 4 The graph shown illustrates the history of the change in the amount of voltage drop during repeated first charge / discharge cycles, and Figure 5 The graph shown illustrates the history of the voltage drop during repeated second charge / discharge cycles. More specifically, Figure 4 It is a 2D graph plotting the self-discharge history data, indicating the change in the amount of voltage drop during repeated first charge / discharge cycles. Figure 4 The graph shows a trend where the voltage drop increases continuously with increasing cycle count. For reference, Figure 4 and 5 It can be obtained from preliminary experimental results of test battery cells manufactured using the same specifications as battery cell BC.

[0079] exist Figure 4 and 5 In the graph, the X-axis indicates the cycle count, and the Y-axis indicates the amount of voltage drop.

[0080] The first charge-discharge cycle may include a process of charging and discharging a single cell BC once in an environment where outdoor air conditions are controlled to a first reference temperature (e.g., 25°C) between the upper and lower limits of a first voltage range (e.g., between 2.5 V and 3.7 V).

[0081] The second charge / discharge cycle may include a process of charging and discharging battery cell BC once within a second reference temperature (e.g., 50°C) in an environment where outdoor air conditions are controlled to a second reference temperature above the first reference temperature, between the upper and lower limits of a second voltage range (e.g., between 2.5 V and 4.2 V). In other words, the second charge / discharge cycle can be a more demanding charge / discharge process than the first charge / discharge cycle because the higher voltage and higher temperature charging / discharge environment is generated by the second charge / discharge cycle compared to the first charge / discharge cycle.

[0082] Each charge / discharge cycle may sequentially include a charging process, a first pause process, a discharging process, and a second pause process. Each charge / discharge cycle may also include a voltage tuning process between the charging process and the first pause process. The voltage tuning process may include applying a constant voltage to match the OCV of the battery cell BC with a reference voltage.

[0083] The charging process in each of the first and second charge / discharge cycles can be performed according to a constant current (CC)-constant voltage (CV) charging protocol. A first current rate can be used for CC charging in the first charge / discharge cycle, and a second current rate can be used for CC charging in the second charge / discharge cycle. The second current rate can be equal to or higher than the first current rate. The charging process in each of the first and second charge / discharge cycles can be performed according to a CC-CV charging protocol. A third current rate can be used for the discharging process in the first charge / discharge cycle, and a fourth current rate can be used for the discharging process in the second charge / discharge cycle. The fourth current rate can be equal to or higher than the third current rate.

[0084] The cycle count can be incremented by 1 at the end of each charge / discharge cycle. A rest period can refer to the time during which battery cell BC stops charging and discharging during the first rest phase of a charge / discharge cycle. Control circuit 130 can determine the amount of voltage drop during each rest period. For reference, a second rest phase is used to minimize polarization during the discharge phase of a charge / discharge cycle of the same number of cycles, and battery cell BC stops charging and discharging for a predetermined time before the charging phase of the next charge / discharge cycle.

[0085] Figure 5 This is a 2D plot of self-discharge history data that indicates the change in the amount of voltage drop during repeated second charge / discharge cycles. Due to the increasing trend of voltage drop... Figure 5 The front of the curve is similar to Figure 4 The curve, but with Figure 4 Conversely, the voltage drop curve changes from an increasing trend to a decreasing trend as the cycle count increases. Figure 5 In the diagram, the symbol K indicates the count of cycles in the pattern of change of the amount of voltage drop, from an increasing trend to a decreasing trend.

[0086] For reference, the timing of the trend change from increasing to decreasing can rely on the history of irregularly changing usage conditions (e.g., charging / discharging current, charging / discharging voltage, temperature, and main SOC range) throughout the life of the battery cell BC.

[0087] In numerous experiments, the inventors have observed that in the initial stage (beginning of life (BOL)), cell BC degradation is accompanied by a gradual increase in voltage drop during the rest period, a point at which the increase in voltage drop ceases, and a tendency for the voltage drop to decrease from the middle of life (MOL).

[0088] Specifically, assuming that in BOL, the path of a small current in the battery cell BC may increase, resulting in an increased voltage drop, such as... Figure 4 As shown. After the battery cell BC further deteriorates under harsh conditions, in the MOL, byproducts (e.g., lithium metal deposits) accumulated on the electrode surface due to side reactions impede the flow of current through the small current path between the positive and negative electrodes, thereby slowing down self-discharge, such as... Figure 5 As shown.

[0089] Furthermore, through numerous experimental results, the inventors have recognized that the amount of gas generated in the battery cell BC increases significantly based on events indicating a shift from an increasing trend to a decreasing trend. Therefore, to increase the safety and lifespan of the battery cell BC, it is necessary to modify the control strategy of the battery cell BC based on the identified trends in the increasing and decreasing trends within the self-discharge history data.

[0090] Figure 6 This is a schematic flowchart illustrating a battery diagnostic method according to the present disclosure. Figure 6 The method can be executed periodically in a repetitive manner.

[0091] refer to Figures 1 to 6 In step S600, the control circuit 130 can determine whether the rest period of the battery cell BC has started. When the value of step S600 is "yes", Figure 6 The method can be moved to step S610. When the value of step S600 is "No", step S610 can be executed again or Figure 6 The method can be completed.

[0092] In step S610, the control circuit 130 can determine the amount of voltage drop of the battery cell BC based on voltage measurement signals collected from the sensing unit 110 at least twice during the rest period.

[0093] In step S620, the control circuit 130 can generate self-discharge history data indicating the changes in the amount of voltage drop during multiple rest periods.

[0094] Specifically, when the voltage drop determined in step S610 is the voltage drop during the Mth rest period (M is a natural number of 2 or greater), the self-discharge history data generated in step S620 can be a set of M voltage drop values ​​arranged in chronological order to determine the value of each voltage drop. For example, before performing step S610, the self-discharge history data can include the values ​​of the first to the (M-1)th voltage drops, and when the value of the Mth voltage drop is determined by step S610, the self-discharge history data can be updated to include the value of the Mth voltage drop from step S620. Through the update function in step S620, the self-discharge history data can include the values ​​of the first to the Mth voltage drops arranged in chronological order.

[0095] In step S630, the control circuit 130 diagnoses the self-discharge state of battery cell BC based on self-discharge history data. (See below for further details.) Figure 7 The detailed process of step S630 is described in more detail.

[0096] In step S640, the control circuit 130 performs a protection process for the battery cell BC based on the results of the diagnosis performed in step S640. Step S640 is optional and can be adjusted as needed. Figure 6 The method is omitted below. Figure 8 The detailed process of step S640 is described in more detail.

[0097] Figure 7 The illustration includes Figure 6 An exemplary flowchart of a sub-step of step S630 in the method.

[0098] refer to Figure 7 In step S710, the control circuit 130 can identify, from the self-discharge history data, the changing pattern of the amount of voltage drop during multiple rest periods as either an increasing trend or a decreasing trend.

[0099] As an example, when the current voltage drop (the amount of the Mth voltage drop) is greater than the previous voltage drop (the amount of the (M-1th voltage drop), the change pattern can be identified as an increasing trend; otherwise, the change pattern can be identified as a decreasing trend.

[0100] As another example, when M is greater than u (preset to be a natural number of 2 or greater), the control circuit 130 can determine an approximate straight line by applying least squares to data points indicating the amount of the Mu-th voltage drop to the M-th voltage drop. When the slope of the approximate straight line is positive, the change pattern can be identified as an increasing trend; otherwise, the change pattern can be identified as a decreasing trend.

[0101] For reference, generally, an increasing trend precedes a decreasing trend, and taking this characteristic into account, the control circuit 130 can identify whether a decreasing trend exists in the self-discharge history data, provided that an increasing trend has already been identified.

[0102] In step S720, the control circuit 130 can determine whether an increasing trend was identified in step S710. When the value of step S720 is "yes", step S730 can be executed. If the value of step S720 is "no", it indicates that a decreasing trend was identified in step S710, and in this case, step S740 can be executed.

[0103] In step S730, the control circuit 130 can determine a first risk level caused by the increasing trend. The first risk level can be an indicator of the above reference... Figure 3 The type of diagnostic parameter describing the likelihood or severity level of an internal short circuit.

[0104] The control circuit 130 can determine a first risk level based on the strength of the increasing trend. The strength of the increasing trend can include the difference between the current voltage drop (the amount of the Mth voltage drop) and the previous voltage drop (the amount of the (M-1)th voltage drop) and / or the absolute value of the slope of an approximate straight line.

[0105] In step S740, the control circuit 130 can determine a second risk level caused by the decreasing trend. The second risk level can be an indication of the above reference... Figure 5 The type of diagnostic parameter describing the likelihood or severity of excessive gas generation.

[0106] The control circuit 130 can determine a second risk level based on the strength of the decreasing trend. The strength of the decreasing trend can include the difference between the current voltage drop (the amount of the Mth voltage drop) and the previous voltage drop (the amount of the (M-1)th voltage drop) and / or the absolute value of the slope of an approximate straight line.

[0107] Figure 8 The illustration includes Figure 6 An exemplary flowchart of a sub-step of step S640 in the method.

[0108] refer to Figure 8 In step S810, the control circuit 130 may perform a first operation to limit the permissible charging / discharging conditions based on the result of diagnosing the self-discharge state of the battery cell BC. The permissible charging / discharging conditions include at least one of the temperature range, SOC range, voltage range, maximum charging current, and maximum discharging current of the battery cell BC.

[0109] The memory 131 can record first relationship data between the limit amount of the allowable charging / discharging conditions and the first risk level, and second relationship data between the limit amount of the allowable charging / discharging conditions and the second risk level.

[0110] The control circuit 130 can perform a first operation by referring to first relationship data when an increasing trend is identified, and can also perform a first operation by referring to second relationship data when a decreasing trend is identified.

[0111] For example, as the second risk level increases, the upper limit of at least one of the permissible temperature range, SOC range, and voltage range of a single battery cell BC can be reduced. In particular, when the upper limit of temperature is reduced by a first operation performed in response to an identified decreasing trend, the technical effects of slowing gas generation and significantly reducing the risk of fire or explosion can be expected.

[0112] A decreasing trend is a strong indication of a very large amount of gas generated in the battery cell BC, and the large amount of gas accumulated in the battery cell BC may easily trigger an explosion of the battery cell BC. Therefore, a decreasing trend exhibits a higher level of danger than an increasing trend. Thus, when the strength of the decreasing trend is equal to the strength of the increasing trend, the limit for permissible charge / discharge conditions based on the second relationship data can be set to a predetermined value larger than the limit for permissible charge / discharge conditions based on the first relationship data.

[0113] In step S820, the control circuit 130 may perform a second operation to determine the recommended timing for the next rest period to be allocated to the battery cell BC. Third relationship data between the allowed period and the first risk level, and fourth relationship data between the allowed period and the second risk level, may be recorded in the memory 131.

[0114] The control circuit 130 can determine the permissible time period by referring to third relationship data when an increasing trend is identified, and can also determine the permissible time period by referring to fourth relationship data when a decreasing trend is identified. Subsequently, the control circuit 130 can determine the time following the permissible time period from the current time as the recommended timing for the next rest period. For example, when the second risk level is higher, the recommended timing for the next rest period can be earlier.

[0115] When the recommended time period is reached, users of battery system 1 can be encouraged to allocate rest periods to re-diagnose the self-discharge status.

[0116] In step S830, the control circuit 130 may perform a third operation by outputting a diagnostic message indicating the result of diagnosing the self-discharge state of the battery cell BC. The diagnostic message may include information indicating at least one of charging / discharging conditions limited by the first operation and a recommended timing determined by the second operation. The diagnostic message may also include alarm information for notifying a first risk level or a second risk level.

[0117] Diagnostic messages can be sent from control circuit 130 to system controller 2 via communication circuit 150. System controller 2 can control the information output device (not shown) of battery system 1 to visually and / or audibly output the information contained in the diagnostic messages to the user.

[0118] Any one or two of steps S810, S820 and S830 can be obtained from Figure 8 The method is omitted. Furthermore, the order in which steps S810, S820, and S830 are executed is not limited to... Figure 8 For example, step S810 can be executed after step S820. As another example, when... Figure 8 If steps S810 and S820 are omitted in the method, step S830 can be executed immediately after step S630 ends.

[0119] The embodiments of this disclosure as described above are not limited to apparatuses and methods, but can also be implemented by a program that performs functions corresponding to the exemplary configurations of this disclosure or by a recording medium having programs recorded thereon, and such implementations can be readily implemented by those skilled in the art from the disclosure of the previously described embodiments.

[0120] Although this disclosure has been described above with reference to certain embodiments and drawings, this disclosure is not limited thereto, and it will be apparent to those skilled in the art that various modifications and changes can be made to it in terms of its technical aspects and within the scope of the appended claims and their equivalents.

[0121] Furthermore, since those skilled in the art can make many substitutions, modifications and changes to this disclosure as described above without departing from the technical aspects of this disclosure, this disclosure is not limited to the above embodiments and drawings, and some or all of the embodiments can be selectively combined to allow for various modifications.

Claims

1. A battery diagnostic device, comprising: A sensing unit configured to measure the voltage of a single battery cell; as well as A control circuit configured to determine the amount of voltage drop of the battery cell during each rest period based on voltage measurement signals collected from the sensing unit at least twice during each rest period. The control circuit is configured as follows: Generate self-discharge history data indicating the change in the amount of voltage drop during the plurality of rest periods, and The self-discharge status of the battery cell is diagnosed based on the self-discharge history data.

2. The battery diagnostic device according to claim 1, in, The control circuit is configured as follows: When an increasing trend in the amount of voltage drop is identified from the self-discharge history data, a first risk level caused by the increasing trend is determined.

3. The battery diagnostic device according to claim 2, in, The control circuit is configured as follows: The first risk level is determined based on the strength of the increasing trend; and Generate an alert message to warn of the first risk level.

4. The battery diagnostic device according to claim 1, in, The control circuit is configured as follows: When a decreasing trend in the amount of voltage drop is identified from the self-discharge history data, a second risk level caused by the decreasing trend is determined.

5. The battery diagnostic device according to claim 4, in, The control circuit is configured as follows: The second risk level is determined based on the strength of the decreasing trend; and Generate an alert message to warn of the second risk level.

6. The battery diagnostic device according to claim 1, in, The control circuit is configured as follows: Based on the results of the diagnosis of the self-discharge state, protection operations are performed on the individual battery cells.

7. The battery diagnostic device according to claim 6, in, The protection operation includes at least one of the following: The first operation is to limit the permissible charging / discharging conditions, which include at least one of the temperature range, state of charge range, voltage range, maximum charging current, and maximum discharging current of the battery cell. The second operation is to determine the recommended timing for the next rest period to be allocated to the battery cell; and The third operation is to output a diagnostic message indicating the result of the diagnosis.

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

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

10. A battery diagnostic method, comprising: Based on voltage measurement signals collected at least twice during each rest period, the amount of voltage drop of a single cell during each rest period is determined. Generate self-discharge history data indicating the change in the amount of voltage drop during the plurality of rest periods; as well as The self-discharge status of the battery cell is diagnosed based on the self-discharge history data.

11. The battery diagnostic method according to claim 10, in, Diagnosing the self-discharge state of the battery cell includes: When an increasing trend in the amount of voltage drop is identified from the self-discharge history data, a first risk level caused by the increasing trend is determined.

12. The battery diagnostic method according to claim 10, in, Diagnosing the self-discharge state of the battery cell includes: When a decreasing trend in the amount of voltage drop is identified from the self-discharge history data, a second risk level caused by the decreasing trend is determined.

13. The battery diagnostic method according to claim 10, further comprising: Based on the results of the diagnosis of the self-discharge state, protection operations are performed on the individual battery cells.

14. The battery diagnostic method according to claim 13, in, The protection operation includes at least one of the following: The first operation is to limit the permissible charging / discharging conditions, which include at least one of the temperature range, state of charge range, voltage range, maximum charging current, and maximum discharging current of the battery cell. The second operation is to determine the recommended timing for the next rest period to be allocated to the battery cell; and The third operation is to output a diagnostic message indicating the result of the diagnosis.

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