Battery system, method for determining operating state of battery pack, and related apparatus

Abstract

This specification provides a method and related apparatus for determining the operating state of a battery system and a battery pack. The battery system includes: a battery pack having multiple battery cells; the multiple battery cells include a target battery cell; when the battery pack reaches a discharge cutoff voltage, the voltage of the target battery cell is greater than the voltage of at least one other battery cell; a controller configured to, during the constant current charging and discharging process of the battery pack, acquire and record specified state parameters of the target battery cell as first state parameters when the operating voltage of the battery pack reaches a reference operating voltage; and, after at least a partial constant current charging and discharging process, when the operating voltage of the battery pack changes back to the reference operating voltage, acquire and record specified state parameters of the target battery cell as second state parameters; and determine the operating state of the battery pack based on the change in state parameters between the first and second state parameters. Therefore, the operating state of the battery pack can be determined relatively accurately.

Description

Technical Field

[0001] The embodiments in this specification relate to the field of battery technology, specifically to a method for determining the operating state of a battery system and battery pack, as well as related devices. Background Technology

[0002] With the continuous development of energy technology, batteries are widely used in energy storage systems and electric vehicles. As a key component of energy storage systems or electric vehicles, the operating status of batteries directly affects the performance, safety, and lifespan of these systems or vehicles. Therefore, accurately detecting and evaluating the operating status of battery packs is of great significance.

[0003] However, the accuracy of existing methods for detecting the operating status of battery packs is not high. Summary of the Invention

[0004] Several embodiments of this specification provide a method and related apparatus for determining the operating state of a battery system and battery pack, which can determine the operating state of the battery relatively accurately.

[0005] This specification provides a battery system comprising: a battery pack having a plurality of battery cells; the plurality of battery cells including a target battery cell; when the battery pack finishes discharging, the voltage of the target battery cell is greater than the voltage of at least one other battery cell; a controller configured to: acquire and record a specified state parameter of the target battery cell as a first state parameter when the operating voltage of the battery pack reaches a reference operating voltage during constant current charging and discharging of the battery pack; and acquire and record a specified state parameter of the target battery cell as a second state parameter when the operating voltage of the battery pack changes back to the reference operating voltage after at least a partial constant current charging and discharging process; and determine the operating state of the battery pack based on the change in state parameter between the first state parameter and the second state parameter.

[0006] In some embodiments, determining the operating state of the battery pack based on the change in state parameters between the first state parameter and the second state parameter includes: comparing the change in state parameters with a specified change threshold, and determining the operating state of the battery pack based on the comparison result; wherein the specified change threshold is: the expected change in the specified state parameter of a battery cell in a critical operating state before and after performing the at least partial constant current charge-discharge process; the battery cell in the critical operating state has an internal short-circuit current that causes the temperature of at least a portion of the solid electrolyte interface film to reach the decomposition temperature.

[0007] In some embodiments, the specified state parameter includes the charge of the target battery cell; the state parameter change includes the charge change of the target battery cell; the specified change threshold includes a charge change threshold; determining the operating state of the battery pack based on the comparison result includes: if the charge change is greater than the charge change threshold, determining that the battery pack is in an abnormal operating state; or, if the charge change is less than the charge change threshold, determining that the battery pack is in a safe operating state.

[0008] In some embodiments, the internal short-circuit current of a battery cell when it is in the critical operating state is used as the internal short-circuit current threshold; the controller is further configured to determine the charge change threshold based on the charge and discharge parameters of the at least partial constant current charge and discharge process and the internal short-circuit current threshold.

[0009] In some embodiments, the at least partial constant current charge-discharge process includes: charging the battery pack with a specified charging current; and discharging the battery pack with a specified discharging current; determining the charge change threshold based on the charge-discharge parameters of the at least partial constant current charge-discharge process and the internal short-circuit current threshold includes: calculating the charge change threshold based on the specified charging current, the charging duration of the battery pack during the at least partial constant current charge-discharge process, the specified discharging current, and the internal short-circuit current threshold.

[0010] In some embodiments, the specified charging current and the specified discharging current are equal; the charge change threshold is calculated based on the specified charging current, the charging duration of the battery pack during the at least partial constant current charging and discharging process, the specified discharging current, and the internal short-circuit current threshold, including: determining a first calculation factor by multiplying the product of the specified charging current, the charging duration, and the internal short-circuit current threshold; calculating the sum of the specified charging current and the internal short-circuit current threshold as a second calculation factor; and dividing the first calculation factor by the second calculation factor to obtain the charge change threshold.

[0011] In some embodiments, the specified state parameter includes the single-cell voltage of the target battery cell; the state parameter change includes the voltage change of the target battery cell; the specified change threshold includes a voltage change threshold; determining the operating state of the battery pack based on the comparison result includes: if the voltage change is greater than the voltage change threshold, determining that the battery pack is in an abnormal operating state; or, if the voltage change is less than the voltage change threshold, determining that the battery pack is in a safe operating state.

[0012] In some embodiments, the first state parameter includes a first cell voltage of the target battery cell; an internal short-circuit current when the battery cell is in a critical operating state, as an internal short-circuit current threshold; the controller is further configured to determine the charge amount of the corresponding target battery cell based on the first cell voltage, as a first charge amount; determine a charge change threshold based on the charge and discharge parameters of the at least partial constant current charge and discharge process and the internal short-circuit current threshold; the charge change threshold is the expected change in charge amount of the battery cell in the critical operating state before and after the at least partial constant current charge and discharge process; calculate the sum of the first charge amount and the charge change threshold as a reference charge amount; determine the cell voltage of the target battery cell corresponding to the reference charge amount as a reference cell voltage; and determine the difference between the reference cell voltage and the first cell voltage as the voltage change threshold.

[0013] In some embodiments, the at least partial constant current charge-discharge process includes: charging the battery pack with a specified charging current; and discharging the battery pack with a specified discharging current. Determining a charge change threshold based on the charge-discharge parameters of the at least partial constant current charge-discharge process and the internal short-circuit current threshold includes: calculating the charge change threshold based on the specified charging current, the charging duration of the battery pack during the at least partial constant current charge-discharge process, the specified discharging current, and the internal short-circuit current threshold.

[0014] In some embodiments, the specified charging current and the specified discharging current are equal; the charge change threshold is calculated based on the specified charging current, the charging duration of the battery pack during the at least partial constant current charging and discharging process, the specified discharging current, and the internal short-circuit current threshold, including: determining twice the product of the specified charging current, the charging duration, and the internal short-circuit current threshold as a first calculation factor; calculating the sum of the specified charging current and the internal short-circuit current threshold as a second calculation factor; and dividing the first calculation factor by the second calculation factor to obtain the charge change threshold.

[0015] In some embodiments, the internal short-circuit current of a battery cell when it is in a critical operating state is used as the internal short-circuit current threshold. The internal short-circuit current threshold is obtained by simulating the temperature of the solid electrolyte interface film of the battery cell with metal dendrites of different sizes. The size of the metal dendrites corresponding to the condition where the temperature of at least a portion of the solid electrolyte interface film reaches the decomposition temperature is used as the critical size. The internal short-circuit current of the battery cell with metal dendrites of the critical size is determined as the internal short-circuit current threshold.

[0016] In some embodiments, the operating status of the battery pack indicates whether there is a potential internal short circuit in the individual battery cells of the battery pack.

[0017] In some embodiments, the controller is further configured to, when it is determined that the battery pack is in an abnormal operating state, identify an abnormal battery cell among the plurality of battery cells by using the individual cell voltage of the battery cells when the battery pack is at the discharge cut-off voltage.

[0018] This specification provides a method for determining the operating state of a battery pack, wherein the battery pack has multiple battery cells, including a target battery cell; when the battery pack reaches a discharge cutoff voltage, the voltage of the target battery cell is greater than the voltage of at least one other battery cell; the method includes: during constant current charging and discharging of the battery pack, acquiring and recording a specified state parameter of the target battery cell as a first state parameter when the operating voltage of the battery pack reaches a reference operating voltage; after at least a partial constant current charging and discharging process, when the operating voltage of the battery pack changes back to the reference operating voltage, acquiring and recording a specified state parameter of the target battery cell as a second state parameter; and determining the operating state of the battery pack based on the change in state parameters between the first and second state parameters.

[0019] In some embodiments, determining the operating state of the battery pack based on the change in state parameters between the first state parameter and the second state parameter includes: comparing the change in state parameters with a specified change threshold; and determining the operating state of the battery pack based on the comparison result; wherein the specified change threshold is: the expected change in the specified state parameter of a battery cell in a critical operating state before and after performing the at least partial constant current charge-discharge process; and the battery cell in the critical operating state has an internal short-circuit current that causes the temperature of at least a portion of the solid electrolyte interface film to reach the decomposition temperature.

[0020] In some embodiments, the specified state parameter includes the charge of the target battery cell; the state parameter change includes the charge change of the target battery cell; the specified change threshold includes a charge change threshold; determining the operating state of the battery pack based on the comparison result includes: if the charge change is greater than the charge change threshold, determining that the battery pack is in an abnormal operating state; or, if the charge change is less than the charge change threshold, determining that the battery pack is in a safe operating state.

[0021] In some embodiments, the internal short-circuit current of a battery cell when it is in the critical operating state is used as the internal short-circuit current threshold; the method further includes: determining the charge change threshold based on the charge and discharge parameters of the at least partial constant current charge and discharge process and the internal short-circuit current threshold.

[0022] In some embodiments, the at least partial constant current charge-discharge process includes: charging the battery pack with a specified charging current; and discharging the battery pack with a specified discharging current; determining the charge change threshold based on the charge-discharge parameters of the at least partial constant current charge-discharge process and the internal short-circuit current threshold includes: calculating the charge change threshold based on the specified charging current, the charging duration of the battery pack during the at least partial constant current charge-discharge process, the specified discharging current, and the internal short-circuit current threshold.

[0023] In some embodiments, the specified charging current and the specified discharging current are equal; the charge change threshold is calculated based on the specified charging current, the charging duration of the battery pack during the at least partial constant current charging and discharging process, the specified discharging current, and the internal short-circuit current threshold, including: determining a first calculation factor by multiplying the product of the specified charging current, the charging duration, and the internal short-circuit current threshold; calculating the sum of the specified charging current and the internal short-circuit current threshold as a second calculation factor; and dividing the first calculation factor by the second calculation factor to obtain the charge change threshold.

[0024] In some embodiments, the specified state parameter includes the single-cell voltage of the target battery cell; the state parameter change includes the voltage change of the target battery cell; the specified change threshold includes a voltage change threshold; determining the operating state of the battery pack based on the comparison result includes: if the voltage change is greater than the voltage change threshold, determining that the battery pack is in an abnormal operating state; or, if the voltage change is less than the voltage change threshold, determining that the battery pack is in a safe operating state.

[0025] In some embodiments, the first state parameter includes a first cell voltage of the target battery cell; and an internal short-circuit current when the battery cell is in a critical operating state, as an internal short-circuit current threshold. The method further includes: determining the charge amount of the target battery cell corresponding to the first cell voltage, as a first charge amount; determining a charge change threshold based on the charge / discharge parameters of the at least partial constant current charge / discharge process and the internal short-circuit current threshold; wherein the charge change threshold is the expected change in charge amount of the battery cell in the critical operating state before and after the at least partial constant current charge / discharge process; calculating the sum of the first charge amount and the charge change threshold as a reference charge amount; determining the cell voltage of the target battery cell corresponding to the reference charge amount as a reference cell voltage; and determining the difference between the reference cell voltage and the first cell voltage as the voltage change threshold.

[0026] In some embodiments, the at least partial constant current charge-discharge process includes: charging the battery pack with a specified charging current; and discharging the battery pack with a specified discharging current. Determining a charge change threshold based on the charge-discharge parameters of the at least partial constant current charge-discharge process and the internal short-circuit current threshold includes: calculating the charge change threshold based on the specified charging current, the charging duration of the battery pack during the at least partial constant current charge-discharge process, the specified discharging current, and the internal short-circuit current threshold.

[0027] In some embodiments, the specified charging current and the specified discharging current are equal; the charge change threshold is calculated based on the specified charging current, the charging duration of the battery pack during the at least partial constant current charging and discharging process, the specified discharging current, and the internal short-circuit current threshold, including: determining twice the product of the specified charging current, the charging duration, and the internal short-circuit current threshold as a first calculation factor; calculating the sum of the specified charging current and the internal short-circuit current threshold as a second calculation factor; and dividing the first calculation factor by the second calculation factor to obtain the charge change threshold.

[0028] In some embodiments, the internal short-circuit current of a battery cell when it is in a critical operating state is used as the internal short-circuit current threshold. The internal short-circuit current threshold is obtained by simulating the temperature of the solid electrolyte interface film of the battery cell with metal dendrites of different sizes. The size of the metal dendrites corresponding to the condition where the temperature of at least a portion of the solid electrolyte interface film reaches the decomposition temperature is used as the critical size. The internal short-circuit current of the battery cell with metal dendrites of the critical size is determined as the internal short-circuit current threshold.

[0029] In some embodiments, the operating status of the battery pack indicates whether there is a potential internal short circuit in the individual battery cells of the battery pack.

[0030] In some embodiments, the method for determining the operating state of the battery pack further includes: when the battery pack is determined to be in an abnormal operating state, identifying an abnormal battery cell among the plurality of battery cells by using the individual cell voltage of the battery cells when the battery pack is at the discharge cutoff voltage.

[0031] In the various embodiments provided in this specification, the battery system includes multiple battery cells. These multiple battery cells include a target battery cell. When the battery pack reaches the end of its discharge cycle, the voltage of the target battery cell is greater than the voltage of at least one other battery cell. This indicates that the target battery cell experiences less loss during charging and discharging compared to at least one other battery cell, meaning that even when the battery pack reaches its discharge cutoff voltage due to the charge loss of other battery cells, the target battery cell still retains a certain amount of charge. Based on this, after at least one charge-discharge cycle, the amount of charge remaining in the target battery cell will increase to a certain extent, causing a change in the specified state parameters of the target battery cell. Therefore, the controller of the battery system can acquire and record the specified state parameters of the target battery cell as a first state parameter when the battery pack's operating voltage reaches a reference operating voltage during the constant current charging and discharging process of the battery pack; and acquire and record the specified state parameters of the target battery cell as a second state parameter when the battery pack's operating voltage changes back to the reference operating voltage after at least a partial constant current charging and discharging process. Furthermore, based on the change in state parameters between the first and second state parameters, the operating state of the battery pack can be determined. Thus, the operating state of the target battery can be determined more accurately. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of a battery system provided for one embodiment of this specification.

[0034] Figure 2 This is a schematic diagram of the process for a critical size metal dendrite provided for one embodiment of this specification.

[0035] Figure 3 This is a schematic diagram of a battery cell provided for one embodiment of this specification.

[0036] Figure 4 A schematic diagram of a computer device provided for one embodiment of this specification. Detailed Implementation

[0037] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0038] In the description of the embodiments of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0039] The operating status of a battery pack can include whether one or more individual battery cells in the pack have experienced a severe internal short circuit. To detect the operating status of a battery pack, related technologies rely on inconsistencies in parameters such as battery voltage to identify its operating status.

[0040] However, these methods have certain limitations. Specifically, the detection of battery pack operating status is affected by various factors, such as individual battery cell aging, temperature variations in the battery pack's operating environment, and the charge / discharge rate of the battery pack. This makes detection methods based on inconsistencies in parameters such as battery voltage prone to false alarms or missed alarms in practical applications, reducing the accuracy and reliability of diagnosis to some extent.

[0041] Furthermore, although internal short circuits will gradually worsen as the battery continues to operate, causing significant changes in some battery parameters, the detection window during this stage is relatively short. Failure to detect these issues in time could result in serious safety risks to the battery pack.

[0042] To address the aforementioned technical problems, embodiments of this specification provide a method and related apparatus for determining the operating state of a battery system and battery pack. By measuring the changes in the state parameters of a target battery cell before and after a constant current charge-discharge cycle, the operating state of the battery pack can be accurately determined. Specifically, the target battery cell is a battery cell in the battery pack that is in a relatively good operating state. Therefore, during the charge-discharge process of the battery pack, because the target battery cell experiences less loss, it retains a certain amount of charge even when the charge of other battery cells reaches the discharge cutoff voltage. Based on this, after at least one charge-discharge cycle, the remaining charge of the target battery cell will increase, causing a change in its specified state parameters. Therefore, the controller of the battery system can acquire and record the specified state parameters of the target battery cell when the battery pack operating voltage reaches the reference operating voltage, and the specified state parameters when the battery pack operating voltage recovers to the reference operating voltage after at least a partial constant current charge-discharge process, during the constant current charge-discharge process. By comparing the changes between the first state parameter and the second state parameter, the controller can determine the operating status of the battery pack, thereby more accurately distinguishing whether the battery pack is in a safe operating state or an abnormal operating state, solving the technical problem of inaccurate diagnosis of the operating status of the battery pack in the prior art.

[0043] Please see Figure 1 This specification provides a battery system comprising: a battery pack having a plurality of battery cells; the plurality of battery cells including a target battery cell; when the battery pack reaches a discharge cutoff voltage, the voltage of the target battery cell is greater than the voltage of at least one other battery cell; a controller configured to, during the constant current charge-discharge process of the battery pack, acquire and record specified state parameters of the target battery cell as first state parameters when the operating voltage of the battery pack reaches a reference operating voltage; and, after at least a partial constant current charge-discharge process, when the operating voltage of the battery pack changes back to the operating state reference operating voltage, acquire and record specified state parameters of the target battery cell as second state parameters; and determine the operating state of the battery pack based on the change in state parameters between the first and second state parameters.

[0044] The battery system includes a battery pack and a controller. The battery pack is a group of battery cells. Each battery cell is an independent unit within the battery pack, capable of independently storing and releasing electrical energy. The multiple battery cells within the battery pack can be connected in series, in parallel, or in a hybrid series-parallel connection. This embodiment does not impose specific limitations on this connection.

[0045] In some embodiments, the operating status of the battery pack indicates whether there is a potential internal short circuit in the individual battery cells within the battery pack. This potential internal short circuit includes issues such as whether an individual battery cell experiences an internal short circuit current or whether it could cause thermal runaway. This embodiment does not impose specific limitations on this aspect.

[0046] The target battery cell is a battery cell among multiple battery cells that is in relatively good operating condition. Specifically, the target battery cell can be a battery cell among multiple battery cells that does not have internal short-circuit current. Alternatively, the target battery cell can also be a battery cell among multiple battery cells that has a relatively small internal short-circuit current. This embodiment does not impose specific limitations here.

[0047] Cell voltage refers to the voltage of a single battery cell. Specifically, cell voltage can be the open-circuit voltage of a single battery cell.

[0048] The target battery cell can be determined by the individual cell voltage of multiple battery cells at the end of the battery pack discharge.

[0049] Specifically, if a battery cell experiences an internal short-circuit current, there will be some loss when charging or discharging that cell. For example, when charging a battery cell with an internal short-circuit current, the actual amount of charge stored in the cell will be less than the amount of charge added. Similarly, when discharging the cell, the amount of charge actually output to the outside will be less than the amount of charge consumed internally.

[0050] Therefore, during the constant current discharge process of the battery pack, the battery cells that experience internal short-circuit current will reach their discharge cutoff voltage earlier than those that do not experience internal short-circuit current or have a smaller internal short-circuit current, at which point the battery pack will stop discharging. Consequently, the battery cells that do not experience internal short-circuit current or have a smaller internal short-circuit current will still retain a certain amount of charge. Therefore, the battery cells that do not experience internal short-circuit current or have a smaller internal short-circuit current will have a relatively higher voltage.

[0051] Accordingly, by comparing the individual cell voltages of multiple battery cells at the end of the battery pack's discharge, a target battery cell can be identified among the multiple battery cells. The target battery cell can be the battery cell with the highest individual cell voltage. In some embodiments, the target battery cell can also be a battery cell whose individual cell voltage is greater than the average individual cell voltage of the remaining battery cells.

[0052] The reference operating voltage can be a preset operating voltage. For example, the reference operating voltage can be set to the battery pack's discharge cutoff voltage, charging limit voltage, or other preset operating voltage. This embodiment does not impose a specific limitation here.

[0053] Specifying state parameters is used to represent the operating state of a battery cell during the charging and discharging process. For example, the specified state parameters can be the charge level of a battery cell or the cell voltage.

[0054] The first state parameter is a specified state parameter recorded when the battery pack's operating voltage reaches a reference operating voltage. For example, the reference operating voltage can be set to 5V. When the battery pack is at the lower limit of its State of Charge (SOC), its operating voltage is below 5V. As the battery pack is charged with a constant current, when the battery pack's operating voltage reaches 5V, the specified state parameter of the target battery cell can be recorded as the first state parameter.

[0055] The second state parameter is a specified state parameter recorded when the battery pack's operating voltage recovers to the reference operating voltage after at least a partial constant current charge-discharge process. For example, the reference operating voltage can be set to 5V. The current operating voltage of the battery pack is the reference operating voltage. At this time, the battery pack can be charged with constant current, and the corresponding operating voltage of the battery pack will gradually increase. After the battery pack's operating voltage reaches the upper limit of the state of charge or the preset target operating voltage, the battery pack can be discharged with constant current, and the operating voltage of the battery pack will begin to decrease. When the operating voltage of the battery pack drops to 5V, the specified state parameter of the target battery cell can be recorded as the second state parameter.

[0056] The change in state parameters is the difference or absolute value of the difference between the first state parameter and the second state parameter, used to determine the operating status of the battery pack.

[0057] The operating status of a battery pack can indicate whether there are any safety hazards. Specifically, for example, the operating status of a battery pack can indicate whether there is a risk of thermal runaway due to internal short-circuit current.

[0058] A constant current charge-discharge process can represent the operating condition of a battery system under normal operation. Alternatively, a constant current charge-discharge process can represent the operating condition of actively controlling the battery pack to perform constant current charge-discharge to achieve the detection of the battery pack's operating status. Specifically, at least a portion of the constant current charge-discharge process during the period when the controller acquires the first state parameter and the second state parameter is a partial constant current charge-discharge process under normal battery system operation. Alternatively, at least a partial constant current charge-discharge process can also represent part or all of the process of actively controlling the battery pack to perform constant current charge-discharge to achieve the detection of the battery pack's operating status.

[0059] As the number of charge-discharge cycles of the battery pack increases, the charge level of each target battery cell increases at the end of each discharge cycle. This causes a change in the specified state parameters of the target battery cell. Therefore, by analyzing the changes in these state parameters before and after each charge-discharge cycle, the operating state of the battery pack can be determined relatively accurately.

[0060] For ease of explanation, it is assumed that the target battery cell has no internal short-circuit current, and the battery pack also includes abnormal battery cells with internal short-circuit current. After the battery pack's operating voltage reaches the reference operating voltage, and then changes back to the reference operating voltage after a period of constant current charging and discharging, it can be considered that the charge injected into the abnormal battery cell is completely consumed during this process. Part of the charge injected into the abnormal battery cell is lost due to the internal short-circuit current in the abnormal battery cell, and the other part is output to the external load during discharge. Simultaneously, since the amount of charge output to the external load by the target battery cell and the abnormal battery cell is the same during constant current discharge, and the target battery cell has no internal short-circuit current, the portion of charge lost by the abnormal battery cell due to the internal short-circuit current represents the remaining charge of the target battery cell.

[0061] Based on this, since the target battery cell has a certain amount of residual charge and the abnormal battery cell also suffers some loss during charging, the battery pack will reach the charging limit voltage earlier than the abnormal battery cell during charging. This process repeats, and the residual charge in the target battery cell will continuously increase, causing changes in the state parameters of the specified state parameters. Therefore, the operating status of the battery pack can be detected by monitoring the state parameters of the target battery cell.

[0062] In some embodiments, determining the operating state of the battery pack based on the change in state parameters between the first state parameter and the second state parameter includes: comparing the change in state parameters with a specified change threshold, and determining the operating state of the battery pack based on the comparison result; wherein the specified change threshold is: the expected change in a specified state parameter of a battery cell in a critical operating state before and after undergoing at least a partial constant current charge-discharge process; the battery cell in a critical operating state has an internal short-circuit current that causes the temperature of at least a portion of the solid electrolyte interface film to reach the decomposition temperature.

[0063] Internal short-circuit current can cause temperature changes in the solid electrolyte interface film to some extent.

[0064] Solid electrolyte interphase (SEI) is a solid film formed on the surface of battery electrodes, and is simply called SEI film.

[0065] The decomposition temperature is the temperature at which the physical or chemical properties of a solid electrolyte interfacial film change. Specifically, the decomposition temperature can be set to any value between 60°C and 80°C.

[0066] Solid-state electrolyte interfacial membranes play a crucial role in the cycle performance and safety of batteries. Specifically, solid-state electrolyte interfacial membranes can prevent further decomposition of the electrolyte and excessive growth of metals (such as lithium metal).

[0067] However, temperature variations in the solid electrolyte interphase (SEE) membrane can affect its stability and battery safety. Specifically, when the SEE membrane reaches its decomposition temperature, it decomposes. This causes the battery electrodes and electrolyte to re-engage, forming a new SEE membrane, which reduces battery capacity. For example, in the case of a lithium-ion battery, the contact between the graphite anode and the electrolyte, resulting in the formation of a SEE membrane, consumes recyclable lithium within the battery, leading to capacity decay.

[0068] Furthermore, the aforementioned parasitic reactions generate heat, further increasing the temperature in the area where the solid electrolyte interphase (SEI) membrane contacts metal dendrites (such as lithium dendrites). The newly formed SEI membrane is then easily decomposed by high temperatures, creating a vicious cycle. If the generated heat cannot be dissipated in time, the battery temperature will continue to rise until it reaches the membrane's collapse temperature, triggering a larger-area internal short circuit and ultimately leading to thermal runaway.

[0069] Therefore, in this embodiment, when at least a portion of the solid electrolyte interface film reaches its decomposition temperature, it is considered that the battery has experienced a relatively severe internal short circuit, and the corresponding internal short circuit current is taken as the internal short circuit current threshold. When the internal short circuit current reaches the internal short circuit current threshold, the battery cell is considered to be in a critical operating state.

[0070] The specified change threshold is set based on the expected change in specified state parameters of a battery cell in a critical operating state before and after undergoing at least a partial constant current charge-discharge process. The specified change threshold can be obtained through simulation of a battery cell in a critical operating state. Alternatively, the specified change threshold can also be calculated using theoretical formulas. This embodiment does not impose specific limitations here.

[0071] By comparing the changes in state parameters with a specified threshold for change, the operating status of the battery pack can be detected more accurately.

[0072] In some embodiments, the internal short-circuit current threshold can be obtained by simulating the temperature of the solid electrolyte interface film of a battery cell with metal dendrites of different sizes; wherein the size of the metal dendrites corresponding to the condition where the temperature of at least a portion of the solid electrolyte interface film reaches the decomposition temperature is taken as the critical size; and determining the internal short-circuit current of the battery cell with metal dendrites of the critical size as the internal short-circuit current threshold.

[0073] Simulating the temperature of the solid electrolyte interface film in a single battery cell with metal dendrites of different sizes can be achieved by running a specified simulation model on a computer. This specified simulation model can be an electro-thermal-electrochemical coupled model or an electro-thermal coupled model. The specified simulation model can be a three-dimensional battery model or a two-dimensional battery model.

[0074] Specifically, by specifying a simulation model, simulated battery cells with metal dendrites of different sizes can be constructed, and the battery performance can be simulated based on this when the battery has different values ​​of internal short-circuit current.

[0075] Since metal dendrites of different sizes have different resistances, simulating battery cells with metal dendrites of different sizes can determine the temperature of the solid electrolyte interface film when different values ​​of internal short-circuit current appear inside the battery cell. When the simulation shows that the temperature of at least a portion of the solid electrolyte interface film reaches the decomposition temperature, the size of the corresponding metal dendrite in the simulated battery cell can be used as the critical size. Furthermore, the internal short-circuit current threshold can be determined based on the critical size.

[0076] Metal dendrites are dendritic metal structures formed inside a battery due to the uneven deposition of metal ions on the electrode surface. The growth of metal dendrites can lead to internal short circuits, affecting battery performance and safety. For example, the growth of metal dendrites may cause the positive and negative electrodes inside the battery to connect, generating an internal short-circuit current.

[0077] In some embodiments, the metal dendrites may be lithium dendrites, etc. Alternatively, the metal dendrites may also be sodium dendrites, etc. This embodiment is not specifically limited herein.

[0078] The size of metal dendrites can be used to characterize the cross-sectional area of ​​metal dendrites in a test cell. For example, if a test cell constructed using a specified simulation model has metal dendrites in a cuboid or approximately cuboid shape, the size of the metal dendrites can include the length and width of the cross-section. Alternatively, if a test cell constructed using a specified simulation model has metal dendrites in a cylindrical or approximately cylindrical shape, the size of the metal dendrites can include the radius of the cross-section. Of course, a test cell constructed using a specified simulation model can also have metal dendrites of other shapes, and correspondingly, the size of the metal dendrites can be described by other parameters. This embodiment does not impose specific limitations here.

[0079] In some embodiments, please refer to Figure 2 The critical dimension can be determined through the following steps.

[0080] Step S110: Construct a battery cell with metal dendrites of a certain size.

[0081] Step S120: Simulate and analyze the internal temperature changes of a single battery cell during charging and discharging.

[0082] Step S130: Increase the size of metal dendrites when the temperature of at least part of the solid electrolyte interface film of the battery cell is lower than the decomposition temperature.

[0083] Step S140: When the temperature of at least part of the solid electrolyte interface film of the battery cell is greater than the decomposition temperature, the size of the metal dendrite is used as the critical size, and the internal short-circuit current is used as the internal short-circuit current threshold.

[0084] The method of determining the internal short-circuit current of a battery cell with metal dendrites of critical size and using it as the internal short-circuit current threshold can also be obtained by specifying a simulation model.

[0085] In some embodiments, the internal short-circuit current threshold can also be calculated using the critical size.

[0086] First, the resistance of the current path through which the internal short-circuit current flows can be determined by the critical size. This resistance can be used as the path resistance. Specifically, the formula for calculating the path resistance can be expressed by formula (1).

[0087]

[0088] Where R is the path resistance of the current path, ρ is the resistivity of the current path, l is the length of the current path, and A is the cross-sectional area of ​​the current path.

[0089] Since the current path may include metal dendrites, electrode materials connected to the metal dendrites, current collectors, and other related materials, the path resistance of the current path can be calculated from the resistance of each part of the material in the current path.

[0090] Furthermore, the cross-sectional area of ​​each part of the material in the current path is the same as the cross-sectional area of ​​the current path, which can be calculated from the size of the metal dendrite. In some cases, when the metal dendrite is cylindrical, the cross-sectional area of ​​the current path can be calculated using formula (2).

[0091] A=πr 2 (2)

[0092] Where r is the radius of the metal dendrite.

[0093] Please see Figure 3 Let's take a lithium battery as an example. A lithium battery can include a positive current collector, a positive electrode, a separator, a negative electrode, and a negative current collector. Lithium dendrites can appear at the separator, generating an internal short-circuit current when the positive and negative electrodes are connected. Figure 3The dark blue area represents lithium dendrites. Correspondingly, the current path includes the positive current collector, the positive electrode, the lithium dendrites, the negative electrode, and the negative current collector. Therefore, the path resistance can be calculated using formula (3).

[0094]

[0095] Among them, R cc R c R Li R a R ac These are the resistances of the positive current collector, positive electrode, lithium dendrite, negative electrode, and negative current collector, respectively. ρ cc ρ c ρ li ρ a ρ ac These are the resistivity of the positive current collector, positive electrode, lithium dendrite, negative electrode, and negative current collector, respectively. cc l c l Li l a l ac These are the lengths of the positive current collector, the positive electrode, the lithium dendrite, the negative electrode, and the negative current collector, respectively.

[0096] Furthermore, the internal short-circuit current of the individual cell can be calculated based on the individual cell voltage and the resistance of the current path, and this can be used as the internal short-circuit current threshold.

[0097] Specifically, the internal short-circuit current of a single battery cell can be calculated using formula (4).

[0098]

[0099] Among them, I self U is the internal short-circuit current, and U is the operating voltage of a single battery cell.

[0100] In some embodiments, the specified state parameters include the charge amount of the target battery cell; the state parameter change amount includes the charge change amount of the target battery cell; the specified change amount threshold includes the charge change amount threshold; and the battery pack operating state is determined based on the comparison result, including: if the charge change amount is greater than the charge change amount threshold, the battery pack is identified as being in an abnormal operating state; or, if the charge change amount is less than the charge change amount threshold, the battery pack is identified as being in a safe operating state.

[0101] Since the constant current charging and discharging process directly affects the charge level of the target battery cell when the battery pack reaches the reference operating voltage, the charge level can be directly used as a specified state parameter in this embodiment. Accordingly, the first state parameter is the first charge level of the target battery cell. The second state parameter is the second charge level of the target battery cell.

[0102] The charge change refers to the change in the amount of charge remaining in a target battery cell before and after at least a partial constant current charge-discharge process. Specifically, the charge change is the absolute value of the difference between the first charge and the second charge. For example, if the charge of a target battery cell increases from 100 Ah to 101 Ah during one charge-discharge cycle, the charge change is 1 Ah.

[0103] The charge change threshold is set based on the expected change in charge of a battery cell in a critical operating state before and after undergoing at least a partial constant current charge-discharge process. The charge change threshold can be obtained through simulation of a battery cell in a critical operating state. Alternatively, the charge change threshold can be calculated using theoretical formulas. This embodiment does not impose specific limitations on this.

[0104] When the comparison result indicates that the charge change is less than the charge change threshold, it means that the individual battery cells inside the battery pack have not experienced a serious internal short circuit. Specifically, there is no internal short circuit current or the internal short circuit current in the individual battery cells is very small, the temperature of the solid electrolyte interface film has not reached the decomposition temperature, and the battery pack can operate relatively stably. Therefore, the battery pack is considered to be in a safe operating state.

[0105] When the comparison result indicates that the charge change is greater than the charge change threshold, it indicates that at least one battery cell has experienced a serious internal short circuit, requiring appropriate safety measures. Specifically, this may be because the internal short-circuit current of the battery cell exceeds the internal short-circuit current threshold, causing the temperature of the solid electrolyte interface film to rise to its decomposition temperature, thus affecting battery safety. Therefore, the battery pack is considered to be in an abnormal operating state.

[0106] Compared to traditional methods based on voltage inconsistency, charge change-based detection methods offer higher accuracy and reliability. Specifically, charge change directly reflects the impact of internal short-circuit current on the charge of individual battery cells, allowing for early detection of anomalies in the initial stages of an internal short circuit. This mitigates detection delays caused by insignificant voltage parameter changes. Furthermore, charge change monitoring is less susceptible to interference from external factors such as battery aging, further enhancing the robustness of the detection and the feasibility of engineering applications.

[0107] In some embodiments, the controller is further configured to determine a charge change threshold based on the charge and discharge parameters of at least a portion of the constant current charge and discharge process and the internal short-circuit current threshold.

[0108] The internal short-circuit current threshold refers to the internal short-circuit current value generated when a battery cell is in a critical operating state. Specifically, the internal short-circuit current threshold can be obtained through simulation analysis of battery cells in a critical operating state. When the internal short-circuit current reaches the internal short-circuit current threshold, the temperature of at least a portion of the solid electrolyte interface film will reach the decomposition temperature, indicating that the battery cell has entered a thermal runaway state. Of course, the internal short-circuit current threshold can also be obtained through testing and experiments on battery cells in a critical operating state. This embodiment does not impose specific limitations here.

[0109] Charge and discharge parameters are various indicators used to describe the battery charging and discharging process. Specifically, charge and discharge parameters include charging current, discharging current, and charging / discharging duration.

[0110] In some embodiments, at least a partial constant current charge-discharge process includes: charging the battery pack with a specified charging current; and discharging the battery pack to the outside with a specified discharging current; determining a charge change threshold based on the charge-discharge parameters of the at least partial constant current charge-discharge process and an internal short-circuit current threshold includes: calculating the charge change threshold based on the specified charging current, the charging duration of the battery pack during the at least partial constant current charge-discharge process, the specified discharging current, and the internal short-circuit current threshold.

[0111] In some embodiments, the specified charging current and the specified discharging current are equal; the charge change threshold is calculated based on the specified charging current, the charging duration of the battery pack during at least a partial constant current charging and discharging process, the specified discharging current, and the internal short-circuit current threshold, including: determining a first calculation factor by multiplying the product of the specified charging current, the charging duration, and the internal short-circuit current threshold; calculating the sum of the specified charging current and the internal short-circuit current threshold as a second calculation factor; and dividing the first calculation factor by the second calculation factor to obtain the charge change threshold.

[0112] For ease of explanation, let's take the example where the specified charging current and the specified discharging current are equal.

[0113] Assuming a battery cell in critical operating condition has an initial charge Q and a state of charge (SOC) of x% when its battery pack operates at the reference voltage, and the internal short-circuit current is taken as the internal short-circuit current threshold I. self The specified charging current and specified discharging current for constant current charging and discharging of the battery pack are the same and both are I.

[0114] During constant current charging, the state of charge of a single battery cell increases from x% to y%, during which time the amount of charge added is Q. ch Charging time is t ch The charge amount is Q. ch It can be calculated using formula 5.

[0115] Q ch =I*t ch (5)

[0116] Due to the presence of internal short-circuit current, the actual amount of charge stored in the battery cell, Q′ ch Compared to the amount of charge Q ch It has a certain loss. Specifically, the actual amount of charge stored, Q′. ch It can be calculated using formula 6.

[0117]

[0118] During constant current discharge, the discharge time for a single battery cell to change its state of charge from y% to x% is t. dis Because the discharge duration is related to the actual charge Q′ stored in the battery cell. ch Related. Therefore, the discharge duration t dis It can be calculated using formulas 7 and 8.

[0119] Q′ ch =I*t dis +I self *t dis (7)

[0120]

[0121] Therefore, the actual amount of charge released is Q′ dis It can be calculated using formula 9.

[0122]

[0123] Correspondingly, the difference ΔQ between the theoretical discharge and the actual discharge of a battery cell in critical operating condition can be calculated using formula 10.

[0124]

[0125] Because the difference in charge between the theoretical and actual discharge amounts of a battery cell in a critical operating state within the battery pack, ΔQ, is reflected in the charge remaining in the target battery cell, this charge difference ΔQ can be used as a threshold for charge change. Accordingly, in Equation 10, the numerator 2*t of ΔQ is used to calculate... ch *I*I self It can be used as the first factor in the calculation. Calculate the denominator I+I of ΔQ. self This can be used as a second calculation factor. Accordingly, dividing the first calculation factor by the second calculation factor yields the charge change threshold.

[0126] Since the charge change of a target battery cell is related to the voltage change of the target battery cell before and after at least a partial constant current charge-discharge process, and the battery management system can easily detect the cell voltage, the operating status of the battery pack can be detected relatively quickly by using the cell voltage as a specified state parameter and observing the voltage change.

[0127] In some embodiments, the specified state parameters include the single-cell voltage of the target battery cell; the state parameter change includes the voltage change of the target battery cell; the specified change threshold includes the voltage change threshold; and the battery pack's operating state is determined based on the comparison result, including: if the voltage change is greater than the voltage change threshold, the battery pack is identified as being in an abnormal operating state; or, if the voltage change is less than the voltage change threshold, the battery pack is identified as being in a safe operating state.

[0128] In this embodiment, the first state parameter is the first cell voltage of the target battery cell. The second state parameter is the second cell voltage of the target battery cell.

[0129] Voltage change refers to the change in a single cell voltage caused by the change in the amount of charge remaining in the target battery cell before and after at least a partial constant current charge-discharge process. Specifically, the voltage change is the absolute value of the difference between the first cell voltage and the second cell voltage. For example, if the voltage of the target battery cell increases from 4.1V to 4.2V during one charge-discharge cycle, the voltage change is 0.1V.

[0130] The voltage change threshold is set based on the expected voltage change of a battery cell in a critical operating state before and after undergoing at least a partial constant current charge-discharge process. The voltage change threshold can be obtained through simulation of a battery cell in a critical operating state. Alternatively, the voltage change threshold can be calculated using theoretical formulas. This embodiment does not impose specific limitations on this.

[0131] When the comparison result indicates that the voltage change is less than the voltage change threshold, it means that there is no serious internal short circuit in the individual battery cells within the battery pack. Specifically, there is no internal short circuit current or the internal short circuit current in the individual battery cells is very small, the temperature of the solid electrolyte interface film has not reached the decomposition temperature, and the battery pack can operate relatively stably. Therefore, the battery pack is considered to be in a safe operating state.

[0132] When the comparison result indicates that the voltage change exceeds the voltage change threshold, it signifies a severe internal short circuit within at least one battery cell, requiring appropriate safety measures. Specifically, this may be due to the internal short-circuit current exceeding the internal short-circuit current threshold, causing the temperature of the solid electrolyte interface film to rise to its decomposition temperature, thus affecting battery safety. Therefore, the battery pack is deemed to be in an abnormal operating state.

[0133] Compared to traditional detection methods based on voltage changes, the voltage change-based detection method offers higher accuracy and reliability. Furthermore, because the battery management system can easily detect the individual cell voltages, it can quickly assess the battery pack's operational status.

[0134] In some embodiments, the first state parameters include a first cell voltage of the target battery cell; an internal short-circuit current when the battery cell is in a critical operating state, as an internal short-circuit current threshold; the controller is further configured to determine the charge amount of the corresponding target battery cell based on the first cell voltage, as a first charge amount; determine a charge change threshold based on the charge and discharge parameters of at least a partial constant current charge and discharge process and the internal short-circuit current threshold; the charge change threshold is the expected change in charge amount of the battery cell in the critical operating state before and after performing at least a partial constant current charge and discharge process; calculate the sum of the first charge amount and the charge change threshold as a reference charge amount; determine the cell voltage of the target battery cell corresponding to the reference charge amount as a reference cell voltage; and determine the difference between the reference cell voltage and the first cell voltage as the voltage change threshold.

[0135] Because the battery management system can relatively easily determine the individual cell voltage of the target battery cell, the controller can acquire the individual cell voltage of the target battery cell and record it as the first individual cell voltage before at least part of the constant current charge / discharge process, when the battery pack's operating voltage reaches the reference operating voltage. The first individual cell voltage can be determined via V... 1,BMS express.

[0136] Furthermore, the first cell voltage V can be determined using the cell voltage-charge curve. 1,BMS The first charge of the corresponding target battery cell. The first charge can be determined by... In some embodiments, the correspondence between the cell voltage and charge of a target battery cell can be stored in a data table, and the first charge corresponding to the first cell voltage can be matched by looking up the table.

[0137] Furthermore, after at least a partial constant current charge-discharge process, when the battery pack's operating voltage returns to the reference operating voltage, the charge change threshold can be determined based on the charge-discharge parameters and the internal short-circuit current threshold. The charge change threshold can be represented by ΔQ. The method for determining the charge change threshold ΔQ can be found in other embodiments of this specification, which will not be elaborated upon here.

[0138] Please refer to Formula 11, and specify the first charge amount. The sum of the charge change and the threshold value ΔQ is used as the reference charge. The reference charge can be obtained through... The reference charge quantity represents the expected charge remaining in a target battery cell after at least a partial constant current charge-discharge process, assuming the presence of abnormal battery cells in the battery pack.

[0139]

[0140] The reference charge can be determined using a single-unit voltage-charge curve or by looking up a table. The voltage of the target battery cell is used as the reference cell voltage. The reference cell voltage can be represented by V2. Correspondingly, the voltage change threshold can be calculated using Equation 12.

[0141] ΔV=V2―V 1,BMS (12)

[0142] After at least a partial constant current charge-discharge process, when the battery pack's operating voltage returns to the reference operating voltage, the controller can acquire the individual cell voltage of the target battery cell and record it as the second individual cell voltage. The second individual cell voltage can be determined via V... 2,BMS This is expressed as follows. Therefore, the voltage change ΔV BMS It can be obtained from Formula 13.

[0143] ΔV BMS =V 2,BMS ―V 1,BMS (13)

[0144] If ΔV BMS If the value is ≥ΔV, then the battery pack can be considered to be in an abnormal operating state.

[0145] In some embodiments, the controller is further configured to, when the battery pack is determined to be in an abnormal operating state, identify the abnormal battery cell among a plurality of battery cells by using the individual cell voltage of the battery cell when the battery pack is at the discharge cut-off voltage.

[0146] Specifically, when the change in the state parameters of a target battery cell exceeds the threshold for the change in state parameters, it can be considered that there is at least one abnormal battery cell in the battery pack.

[0147] Abnormal battery cells are those with safety risks such as thermal runaway. Abnormal battery cells can be identified by their individual cell voltages when the battery pack is at the discharge cutoff voltage. For example, an abnormal battery cell could be the one with the lowest voltage when the battery pack is at the discharge cutoff voltage. Alternatively, an abnormal battery cell could be one whose voltage is lower than the average voltage of all other battery cells by a certain value when the battery pack is at the discharge cutoff voltage. This embodiment does not impose specific limitations.

[0148] This specification provides a method for determining the operating state of a battery pack, wherein the battery pack has multiple battery cells, including a target battery cell; when the battery pack reaches the discharge cutoff voltage, the voltage of the target battery cell is greater than the voltage of at least one other battery cell; the method includes: during the constant current charge-discharge process of the battery pack, acquiring and recording a specified state parameter of the target battery cell as a first state parameter when the operating voltage of the battery pack reaches a reference operating voltage; after at least a partial constant current charge-discharge process, when the operating voltage of the battery pack changes back to the reference operating voltage, acquiring and recording a specified state parameter of the target battery cell as a second state parameter; and determining the operating state of the battery pack based on the change in state parameter between the first and second state parameters.

[0149] In some embodiments, determining the operating state of the battery pack based on the change in state parameters between a first state parameter and a second state parameter includes: comparing the change in state parameters with a specified change threshold; and determining the operating state of the battery pack based on the comparison result; wherein the specified change threshold is: the expected change in a specified state parameter of a battery cell in a critical operating state before and after undergoing at least a partial constant current charge-discharge process; and the battery cell in a critical operating state has an internal short-circuit current that causes the temperature of at least a portion of the solid electrolyte interface film to reach its decomposition temperature.

[0150] In some embodiments, the specified state parameters include the charge amount of the target battery cell; the state parameter change amount includes the charge change amount of the target battery cell; the specified change amount threshold includes the charge change amount threshold; and the battery pack operating state is determined based on the comparison result, including: if the charge change amount is greater than the charge change amount threshold, the battery pack is identified as being in an abnormal operating state; or, if the charge change amount is less than the charge change amount threshold, the battery pack is identified as being in a safe operating state.

[0151] In some embodiments, the internal short-circuit current when a battery cell is in a critical operating state is used as the internal short-circuit current threshold; the method further includes: determining a charge change threshold based on the charge and discharge parameters of at least a portion of the constant current charge and discharge process and the internal short-circuit current threshold.

[0152] In some embodiments, at least a partial constant current charge-discharge process includes: charging the battery pack with a specified charging current; and discharging the battery pack to the outside with a specified discharging current; determining a charge change threshold based on the charge-discharge parameters of the at least partial constant current charge-discharge process and an internal short-circuit current threshold includes: calculating the charge change threshold based on the specified charging current, the charging duration of the battery pack during the at least partial constant current charge-discharge process, the specified discharging current, and the internal short-circuit current threshold.

[0153] In some embodiments, the specified charging current and the specified discharging current are equal; the charge change threshold is calculated based on the specified charging current, the charging duration of the battery pack during at least a partial constant current charging and discharging process, the specified discharging current, and the internal short-circuit current threshold, including: determining a first calculation factor by multiplying the product of the specified charging current, the charging duration, and the internal short-circuit current threshold; calculating the sum of the specified charging current and the internal short-circuit current threshold as a second calculation factor; and dividing the first calculation factor by the second calculation factor to obtain the charge change threshold.

[0154] In some embodiments, the specified state parameters include the single-cell voltage of the target battery cell; the state parameter change includes the voltage change of the target battery cell; the specified change threshold includes the voltage change threshold; and the battery pack's operating state is determined based on the comparison result, including: if the voltage change is greater than the voltage change threshold, the battery pack is identified as being in an abnormal operating state; or, if the voltage change is less than the voltage change threshold, the battery pack is identified as being in a safe operating state.

[0155] In some embodiments, the first state parameter includes a first cell voltage of the target battery cell; and an internal short-circuit current when the battery cell is in a critical operating state, as an internal short-circuit current threshold. The method further includes: determining the charge amount of the corresponding target battery cell based on the first cell voltage, as a first charge amount; determining a charge change threshold based on the charge and discharge parameters of at least a partial constant current charge and discharge process and the internal short-circuit current threshold; wherein the charge change threshold is the expected change in charge amount of the battery cell in the critical operating state before and after undergoing at least a partial constant current charge and discharge process; calculating the sum of the first charge amount and the charge change threshold as a reference charge amount; determining the cell voltage of the target battery cell corresponding to the reference charge amount as a reference cell voltage; and determining the difference between the reference cell voltage and the first cell voltage as the voltage change threshold.

[0156] In some embodiments, at least a partial constant current charge-discharge process includes: charging the battery pack with a specified charging current; and discharging the battery pack to the outside with a specified discharging current; determining a charge change threshold based on the charge-discharge parameters of the at least partial constant current charge-discharge process and an internal short-circuit current threshold includes: calculating the charge change threshold based on the specified charging current, the charging duration of the battery pack during the at least partial constant current charge-discharge process, the specified discharging current, and the internal short-circuit current threshold.

[0157] In some embodiments, the specified charging current and the specified discharging current are equal; the charge change threshold is calculated based on the specified charging current, the charging duration of the battery pack during at least a partial constant current charging and discharging process, the specified discharging current, and the internal short-circuit current threshold, including: determining twice the product of the specified charging current, the charging duration, and the internal short-circuit current threshold as a first calculation factor; calculating the sum of the specified charging current and the internal short-circuit current threshold as a second calculation factor; and dividing the first calculation factor by the second calculation factor to obtain the charge change threshold.

[0158] In some embodiments, the internal short-circuit current of a battery cell when it is in a critical operating state is used as the internal short-circuit current threshold. The internal short-circuit current threshold is obtained by simulating the temperature of the solid electrolyte interface film of the battery cell with metal dendrites of different sizes; wherein the size of the metal dendrites corresponding to the condition where the temperature of at least a portion of the solid electrolyte interface film reaches the decomposition temperature is used as the critical size; and the internal short-circuit current of the battery cell with metal dendrites of the critical size is determined as the internal short-circuit current threshold.

[0159] In some embodiments, the operating status of the battery pack indicates whether there is a potential internal short circuit in the individual battery cells within the battery pack.

[0160] In some embodiments, the method for determining the operating state of the battery pack further includes: when the battery pack is determined to be in an abnormal operating state, identifying an abnormal battery cell among multiple battery cells by using the individual cell voltage of the battery cells when the battery pack is at the discharge cutoff voltage.

[0161] For a description of the method for determining the operating status of the battery pack, please refer to other embodiments in this specification. This embodiment will not be elaborated upon further here.

[0162] This specification also provides a battery management system, including a method for determining the operating state of a battery pack as described in any embodiment of this specification.

[0163] For a description of the battery management system, please refer to other embodiments in this specification. This embodiment will not be elaborated upon further here.

[0164] This specification also provides an energy storage system, including the battery system described in any embodiment of this specification.

[0165] For a description of the energy storage system, please refer to other embodiments in this specification. This embodiment will not be elaborated upon further here.

[0166] Please see Figure 4 This specification also provides a computer device, which includes a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, it implements the method for determining the working state of a battery as described in any of the above embodiments; or, when the processor executes the computer program, it implements the battery simulation method as described in any of the above embodiments.

[0167] This specification also provides a storage medium storing a computer program, which, when executed by a processor, implements the method for determining the working state of a battery as described in any of the above embodiments; or, when the processor executes the computer program, it implements the battery simulation method as described in any of the above embodiments.

[0168] It is understood that the term "connection" in the following embodiments should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc. can transmit electrical signals or data to each other.

[0169] It is understood that the specific examples in this document are only intended to help those skilled in the art better understand the embodiments of this specification, and are not intended to limit the scope of the invention.

[0170] It is understood that in the various embodiments of this specification, the sequence number of each process does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this specification.

[0171] It is understood that the various embodiments described in this specification can be implemented individually or in combination, and the embodiments in this specification are not limited in this respect.

[0172] Unless otherwise stated, all technical and scientific terms used in the embodiments of this specification have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of this specification. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items. The singular forms "a," "the," and "the" as used in the embodiments of this specification and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0173] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this specification.

[0174] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0175] As should be understood from the several embodiments provided in this specification, the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0176] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0177] The above description is merely a specific embodiment of this specification, but the scope of protection of this invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this specification should be included within the scope of protection of this specification. Therefore, the scope of protection of this invention should be determined by the scope of the claims.

Claims

1. A battery system, characterized in that, include: A battery pack having multiple battery cells; the multiple battery cells include a target battery cell; when the battery pack is discharged, the voltage of the target battery cell is greater than the voltage of at least one other battery cell. The controller is configured to: acquire a specified state parameter of the target battery cell when the operating voltage of the battery pack reaches a reference operating voltage during the constant current charging and discharging process of the battery pack, and record it as a first state parameter; and acquire a specified state parameter of the target battery cell and record it as a second state parameter when the operating voltage of the battery pack changes back to the reference operating voltage after at least a partial constant current charging and discharging process; and determine the operating state of the battery pack based on the change in state parameters between the first state parameter and the second state parameter.

2. The battery system according to claim 1, characterized in that, The operating state of the battery pack is determined based on the change in state parameters between the first state parameter and the second state parameter, including: The change in the state parameter is compared with a specified change threshold, and the operating state of the battery pack is determined based on the comparison result; wherein, the specified change threshold is: the expected change in the specified state parameter of a battery cell in a critical operating state before and after the at least part of the constant current charge and discharge process; the battery cell in the critical operating state has an internal short-circuit current that causes the temperature of at least a part of the solid electrolyte interface film to reach the decomposition temperature.

3. The battery system according to claim 2, characterized in that, The specified state parameters include the charge of the target battery cell; the change in state parameters includes the change in charge of the target battery cell. The specified change threshold includes the charge change threshold; Determining the operating status of the battery pack based on the comparison results includes: identifying the battery pack as being in an abnormal operating state if the charge change is greater than the charge change threshold. Alternatively, if the change in charge is less than the threshold value for the change in charge, the battery pack is considered to be in a safe operating state.

4. The battery system according to claim 3, characterized in that, The internal short-circuit current of a single battery cell when it is in the critical operating state is used as the internal short-circuit current threshold. The controller is also configured to determine the charge change threshold based on the charge and discharge parameters of the at least partial constant current charge and discharge process and the internal short-circuit current threshold.

5. The battery system according to claim 4, characterized in that, The at least partial constant current charge-discharge process includes: charging the battery pack with a specified charging current; and discharging the battery pack to the outside with a specified discharging current. Determining the charge change threshold based on the charge and discharge parameters of the at least partial constant current charge and discharge process and the internal short-circuit current threshold includes: calculating the charge change threshold based on the specified charging current, the charging duration of the battery pack during the at least partial constant current charge and discharge process, the specified discharge current, and the internal short-circuit current threshold.

6. The battery system according to claim 5, characterized in that, The specified charging current and the specified discharging current are equal; The charge change threshold is calculated based on the specified charging current, the charging duration of the battery pack during at least a partial constant current charging and discharging process, the specified discharging current, and the internal short-circuit current threshold, including: determining twice the product of the specified charging current, the charging duration, and the internal short-circuit current threshold as a first calculation factor; The sum of the specified charging current and the internal short-circuit current threshold is calculated as a second calculation factor; the first calculation factor is divided by the second calculation factor to obtain the charge change threshold.

7. The battery system according to claim 2, characterized in that, The specified state parameters include the single-cell voltage of the target battery cell; the change in state parameters includes the change in voltage of the target battery cell. The specified change threshold includes the voltage change threshold; Determining the operating status of the battery pack based on the comparison results includes: identifying the battery pack as being in an abnormal operating state if the voltage change is greater than the voltage change threshold. Alternatively, if the voltage change is less than the voltage change threshold, the battery pack is considered to be in a safe operating state.

8. The battery system according to claim 7, characterized in that, The first state parameters include the first cell voltage of the target battery cell; and the internal short-circuit current when the battery cell is in a critical operating state, which is used as the internal short-circuit current threshold. The controller is also configured to determine the charge amount of the corresponding target battery cell based on the first cell voltage, and use it as the first charge amount; The charge change threshold is determined based on the charge and discharge parameters of the at least partial constant current charge and discharge process and the internal short-circuit current threshold. The charge change threshold is the expected change in charge of a battery cell in the critical operating state before and after undergoing the at least partial constant current charge and discharge process; Calculate the sum of the first charge quantity and the charge change threshold, and use it as the reference charge quantity; The single-cell voltage of the target battery cell corresponding to the reference charge is determined and used as the reference single-cell voltage; The difference between the reference cell voltage and the first cell voltage is determined as the voltage change threshold.

9. The battery system according to claim 8, characterized in that, The at least partial constant current charge-discharge process includes: charging the battery pack with a specified charging current; and discharging the battery pack to the outside with a specified discharging current. Determining the charge change threshold based on the charge and discharge parameters of the at least partial constant current charge and discharge process and the internal short-circuit current threshold includes: calculating the charge change threshold based on the specified charging current, the charging duration of the battery pack during the at least partial constant current charge and discharge process, the specified discharge current, and the internal short-circuit current threshold.

10. The battery system according to claim 9, characterized in that, The specified charging current and the specified discharging current are equal; The charge change threshold is calculated based on the specified charging current, the charging duration of the battery pack during at least a partial constant current charging and discharging process, the specified discharging current, and the internal short-circuit current threshold, including: The first calculation factor is determined by multiplying the specified charging current, the charging duration, and the internal short-circuit current threshold by twice its product. The sum of the specified charging current and the internal short-circuit current threshold is calculated as a second calculation factor. Divide the first calculation factor by the second calculation factor to obtain the charge change threshold.

11. The battery system according to claim 2, characterized in that... The internal short-circuit current of a single battery cell when it is in a critical operating state is used as the internal short-circuit current threshold; the internal short-circuit current threshold is obtained in the following way: The temperature of the solid electrolyte interface film in a simulated battery cell with metal dendrites of different sizes is defined as the size of the metal dendrites corresponding to the condition where the temperature of at least a portion of the solid electrolyte interface film reaches the decomposition temperature. The internal short-circuit current of a battery cell with metal dendrites of a critical size is determined as the internal short-circuit current threshold.

12. The battery system according to any one of claims 1 to 11, characterized in that, The operating status of the battery pack indicates whether there is a risk of internal short circuit in the individual battery cells within the battery pack.

13. The battery system according to any one of claims 1 to 11, characterized in that, The controller is also used to identify the abnormal battery cell among the plurality of battery cells by using the individual cell voltage of the battery cells when the battery pack is at the discharge cut-off voltage, when the battery pack is determined to be in an abnormal operating state.

14. A method for determining the operating state of a battery pack, characterized in that, The battery pack has multiple battery cells; the multiple battery cells include the target battery cell; When the battery pack reaches the discharge cutoff voltage, the voltage of the target battery cell is greater than the voltage of at least one other battery cell; the method includes: During the constant current charging and discharging process of the battery pack, the specified state parameters of the target battery cell are obtained when the operating voltage of the battery pack reaches the reference operating voltage and recorded as the first state parameters; After at least a partial constant current charge and discharge process, when the operating voltage of the battery pack changes back to the reference operating voltage, the specified state parameters of the target battery cell are obtained and recorded as the second state parameters. The operating state of the battery pack is determined based on the change in state parameters between the first state parameter and the second state parameter.

15. The method according to claim 14, characterized in that, The operating state of the battery pack is determined based on the change in state parameters between the first state parameter and the second state parameter, including: The change in the state parameter is compared with a specified change threshold. The operating state of the battery pack is determined based on the comparison results; wherein, the specified change threshold is: the expected change of the specified state parameter of the battery cell in the critical operating state before and after the at least part of the constant current charge and discharge process; the battery cell in the critical operating state has an internal short-circuit current that causes the temperature of at least a part of the solid electrolyte interface film to reach the decomposition temperature.

16. The method according to claim 15, characterized in that, The specified state parameters include the charge of the target battery cell; the change in state parameters includes the change in charge of the target battery cell. The specified change threshold includes the charge change threshold; The operating status of the battery pack is determined based on the comparison results, including: If the charge change exceeds the charge change threshold, the battery pack is deemed to be in an abnormal operating state. or, If the change in charge is less than the threshold value for the change in charge, the battery pack is considered to be in a safe operating state.

17. The method according to claim 16, characterized in that, The internal short-circuit current of a single battery cell when it is in the critical operating state is used as the internal short-circuit current threshold; the method further includes: The charge change threshold is determined based on the charge and discharge parameters of the at least partial constant current charge and discharge process and the internal short-circuit current threshold.

18. The method according to claim 17, characterized in that, The at least partial constant current charge-discharge process includes: charging the battery pack with a specified charging current; and discharging the battery pack to the outside with a specified discharging current. Determining the charge change threshold based on the charge and discharge parameters of the at least partial constant current charge and discharge process and the internal short-circuit current threshold includes: calculating the charge change threshold based on the specified charging current, the charging duration of the battery pack during the at least partial constant current charge and discharge process, the specified discharge current, and the internal short-circuit current threshold.

19. The method according to claim 18, characterized in that, The specified charging current and the specified discharging current are equal; the charge change threshold is calculated based on the specified charging current, the charging duration of the battery pack during at least a partial constant current charging and discharging process, the specified discharging current, and the internal short-circuit current threshold, including: The first calculation factor is determined by multiplying the product of the specified charging current, the charging duration, and the internal short-circuit current threshold by two times. The sum of the specified charging current and the internal short-circuit current threshold is calculated as a second calculation factor. Divide the first calculation factor by the second calculation factor to obtain the charge change threshold.

20. The method according to claim 15, characterized in that, The specified state parameters include the single-cell voltage of the target battery cell; the change in state parameters includes the change in voltage of the target battery cell. The specified change threshold includes the voltage change threshold; The operating status of the battery pack is determined based on the comparison results, including: If the voltage change exceeds the voltage change threshold, the battery pack is deemed to be in an abnormal operating state. or, If the voltage change is less than the voltage change threshold, the battery pack is considered to be in a safe operating state.

21. The method according to claim 20, characterized in that, The first state parameter includes the first cell voltage of the target battery cell; The internal short-circuit current of a single battery cell when it is in a critical operating state is used as the internal short-circuit current threshold; the method further includes: Based on the first cell voltage, the charge amount of the corresponding target battery cell is determined and used as the first charge amount; Based on the charging and discharging parameters of the at least partial constant current charging and discharging process and the internal short-circuit current threshold, a charge change threshold is determined; wherein, the charge change threshold is the expected change in charge of a battery cell in the critical operating state before and after the at least partial constant current charging and discharging process. Calculate the sum of the first charge quantity and the charge change threshold, and use it as the reference charge quantity; The single-cell voltage of the target battery cell corresponding to the reference charge is determined and used as the reference single-cell voltage; The difference between the reference cell voltage and the first cell voltage is determined as the voltage change threshold.

22. The method according to claim 21, characterized in that, The at least partial constant current charge-discharge process includes: charging the battery pack with a specified charging current; and discharging the battery pack to the outside with a specified discharging current. Determining the charge change threshold based on the charge and discharge parameters of the at least partial constant current charge and discharge process and the internal short-circuit current threshold includes: calculating the charge change threshold based on the specified charging current, the charging duration of the battery pack during the at least partial constant current charge and discharge process, the specified discharge current, and the internal short-circuit current threshold.

23. The method according to claim 22, characterized in that, The specified charging current and the specified discharging current are equal; the charge change threshold is calculated based on the specified charging current, the charging duration of the battery pack during at least a partial constant current charging and discharging process, the specified discharging current, and the internal short-circuit current threshold, including: The first calculation factor is determined by multiplying the specified charging current, the charging duration, and the internal short-circuit current threshold by twice its product. The sum of the specified charging current and the internal short-circuit current threshold is calculated as a second calculation factor. Divide the first calculation factor by the second calculation factor to obtain the charge change threshold.

24. The method according to claim 15, characterized in that, The internal short-circuit current of a single battery cell when it is in a critical operating state is used as the internal short-circuit current threshold; the internal short-circuit current threshold is obtained in the following way: The temperature of the solid electrolyte interface film in a simulated battery cell with metal dendrites of different sizes is defined as the size of the metal dendrites corresponding to the condition where the temperature of at least a portion of the solid electrolyte interface film reaches the decomposition temperature. The internal short-circuit current of a battery cell with metal dendrites of a critical size is determined as the internal short-circuit current threshold.

25. The method according to any one of claims 15 to 24, characterized in that, The operating status of the battery pack indicates whether there is a risk of internal short circuit in the individual battery cells within the battery pack.

26. The method according to any one of claims 15 to 24, characterized in that, The method further includes: If the battery pack is determined to be in an abnormal operating state, the abnormal battery cell is identified from the plurality of battery cells by measuring the individual cell voltage when the battery pack is at the discharge cutoff voltage.

27. A battery management system, characterized in that, A method for determining the operating state of a battery pack according to any one of claims 14 to 26.

28. An energy storage system, characterized in that, Includes the battery system according to any one of claims 1 to 13.

29. A computer device, characterized in that, The computer device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the method for determining the operating state of the battery pack according to any one of claims 14 to 26.

30. A storage medium, characterized in that, The storable medium stores a computer program that, when executed by a processor, implements the method for determining the operating state of the battery pack according to any one of claims 14 to 26.

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