A battery pack overcharge diagnosis method, overdischarge diagnosis method and device

Abstract

A battery pack overcharge diagnosis method, overdischarge diagnosis method, and device relate to the technical field of battery management systems. The method includes: setting at least one overcharge level, each overcharge level corresponding to a first voltage threshold and a first capacity threshold; obtaining the maximum voltage of all cells in the battery pack; when the maximum voltage is greater than or equal to the second voltage threshold, the absolute value of the battery pack current is less than or equal to the first current threshold, and the duration reaches a first preset time, integrating the battery pack current in ampere hours; if the absolute value of the capacity increase obtained by the integration is greater than or equal to the first capacity threshold corresponding to a certain overcharge level, the battery pack is determined to be overcharged at that overcharge level; when the maximum voltage is greater than the first voltage threshold corresponding to any overcharge level, the battery pack is determined to be overcharged at that overcharge level. This application combines voltage and capacity to diagnose whether it is overcharged or overdischarged, which can effectively reduce the probability of misjudgment or missed judgment and improve the accuracy and reliability of diagnosis.

Description

Technical Field

[0001] The present application relates to the technical field of battery management systems, and in particular to a battery pack overcharge diagnosis method, over-discharge diagnosis method and device. Background Art

[0002] With the rapid development of applications such as electric vehicles and energy storage devices, battery packs are being used on a large scale. Battery management systems (BMS), as a key technology for monitoring battery pack status and ensuring safe, stable, and efficient operation, have also garnered widespread attention. Battery packs are prone to overcharge and overdischarge at the end of charging and discharging. These conditions can degrade battery pack performance or reduce its lifespan, or even cause fire and explosion, endangering human life and property. Therefore, a battery management system that can accurately and proactively diagnose overcharge and overdischarge is crucial for improving the safety and reliability of battery systems.

[0003] In related technologies, the voltage of each battery cell in a battery pack is compared with a preset voltage threshold. If the voltage exceeds the threshold, the battery pack is judged to be overcharged or over-discharged. However, this method is prone to misjudgment or missed judgment, and cannot effectively protect the safety of the battery pack. Summary of the Invention

[0004] The present application provides a battery pack overcharge diagnosis method, over-discharge diagnosis method and device, which can solve the technical problems in the prior art that are prone to misjudgment or missed judgment.

[0005] In a first aspect, the present application provides a battery pack overcharge diagnosis method, the method comprising:

[0006] Setting at least one overcharge level, each overcharge level corresponding to a first voltage threshold and a first capacity threshold;

[0007] Get the maximum voltage of all cells in the battery pack;

[0008] When the maximum voltage is greater than or equal to the second voltage threshold, the absolute value of the current of the battery pack is less than or equal to the first current threshold, and the duration reaches a first preset time, the battery pack current is integrated in ampere hours; if the absolute value of the capacity increase obtained by the integration is greater than or equal to the first capacity threshold corresponding to a certain overcharge level, the battery pack is determined to be overcharged at that overcharge level; and the second voltage threshold is less than the first voltage threshold corresponding to any overcharge level;

[0009] When the maximum voltage is greater than a first voltage threshold corresponding to any overcharge level, it is determined that the battery pack is overcharged at that overcharge level.

[0010] In combination with the first aspect, in one embodiment, there are multiple overcharge levels, and the first voltage threshold and the first capacity threshold corresponding to the high overcharge level are greater than the first voltage threshold and the first capacity threshold corresponding to the low overcharge level;

[0011] When determining that the battery pack is overcharged at this overcharge level, the following is also included:

[0012] The highest level among the overcharge levels of the battery pack is obtained to generate a maximum overcharge level signal so that the battery management system can execute a corresponding protection mechanism according to the above maximum overcharge level signal.

[0013] In combination with the first aspect, in one embodiment, when the duration reaches a first preset time, the method further includes:

[0014] Obtaining a first cell capacity of the cell corresponding to the maximum voltage and a second cell capacity corresponding to the first voltage threshold;

[0015] A first difference between the second battery cell capacity and the first battery cell capacity is obtained, and the first difference or the product of the first difference and the battery health is used as the first capacity threshold.

[0016] In combination with the first aspect, in one implementation, the second voltage threshold is: a product of a charge cut-off voltage and a first preset coefficient.

[0017] In combination with the first aspect, in one embodiment, before obtaining the maximum voltage of all battery cells in the battery pack, it also includes obtaining the above-mentioned first preset time; the above-mentioned first preset time is: obtained according to the above-mentioned second voltage threshold and the first current threshold.

[0018] In conjunction with the first aspect, in one embodiment, obtaining the first preset time specifically includes:

[0019] Setting a second voltage threshold and a first current threshold according to a charging performance parameter curve;

[0020] The time point at which the voltage is greater than or equal to the second voltage threshold and the absolute value of the current is less than or equal to the first current threshold in the above charging performance parameter curve is the first time point;

[0021] Calculating the absolute value of the instantaneous rate of change of voltage and the absolute value of the instantaneous rate of change of current at each first interval, and calculating the absolute value of the voltage fluctuation value and the absolute value of the current fluctuation value at each second interval, until simultaneously satisfying: the absolute value of the instantaneous rate of change of voltage and the absolute value of the instantaneous rate of change of current are both less than the first preset rate of change, and the absolute value of the voltage fluctuation value and the absolute value of the current fluctuation value are both less than the first preset fluctuation value, and the time point at this time is regarded as the second time point; and the first interval is less than the second interval;

[0022] The time difference between the second time point and the first time point is used as the first preset time.

[0023] In combination with the first aspect, in one implementation, the second interval is three times the first interval.

[0024] In a second aspect, the present application provides a battery pack over-discharge diagnosis method, the method comprising:

[0025] Setting at least one over-discharge level, each over-discharge level corresponding to a third voltage threshold and a second capacity threshold;

[0026] Get the minimum voltage of all cells in the battery pack;

[0027] When the minimum voltage is less than or equal to the fourth voltage threshold, the absolute value of the current of the battery pack is less than or equal to the second current threshold, and the duration reaches a second preset time, the battery pack current is integrated in ampere hours; if the absolute value of the capacity reduction obtained by the integration is greater than or equal to the second capacity threshold corresponding to a certain over-discharge level, the battery pack is determined to be over-discharged at that over-discharge level; and the fourth voltage threshold is greater than the third voltage threshold corresponding to any over-discharge level;

[0028] When the minimum voltage is less than the third voltage threshold corresponding to any over-discharge level, it is determined that the battery pack is over-discharged at the corresponding over-discharge level.

[0029] In conjunction with the second aspect, in one embodiment, there are multiple over-discharge levels, and the third voltage threshold corresponding to the high over-discharge level is lower than the third voltage threshold corresponding to the low over-discharge level, and the second capacity threshold corresponding to the high over-discharge level is higher than the second capacity threshold corresponding to the low over-discharge level;

[0030] When the battery pack is judged to be over-discharged at this over-discharge level, the following is also included:

[0031] The highest over-discharge level among the over-discharge levels of the battery pack is obtained to generate a maximum over-discharge level signal so that the battery management system can execute a corresponding protection mechanism according to the above maximum over-discharge level signal.

[0032] In conjunction with the second aspect, in one embodiment, when the duration reaches a second preset time, the method further includes:

[0033] Obtaining a third cell capacity of the cell corresponding to the minimum voltage and a fourth cell capacity corresponding to the third voltage threshold;

[0034] Obtaining a second difference between the third battery cell capacity and the fourth battery cell capacity, and using the second difference or the product of the second difference and the battery health as the second capacity threshold;

[0035] In combination with the second aspect, in one embodiment, the fourth voltage threshold is: a product of the discharge cut-off voltage and a second preset coefficient;

[0036] In combination with the second aspect, in one embodiment, before obtaining the minimum voltage of all battery cells in the battery pack, it also includes obtaining the above-mentioned second preset time; the above-mentioned second preset time is: obtained according to the above-mentioned fourth voltage threshold and the second current threshold.

[0037] In conjunction with the second aspect, in one embodiment, obtaining the second preset time specifically includes:

[0038] setting a fourth voltage threshold and a second current threshold according to a discharge performance parameter curve;

[0039] The time point at which the voltage reaches or is equal to the fourth voltage threshold for the first time and the absolute value of the current is equal to or less than the third current threshold in the above-mentioned discharge performance parameter curve is referred to as the third time point;

[0040] The absolute value of the instantaneous rate of change of voltage and the absolute value of the instantaneous rate of change of current are calculated at each third interval, and the absolute value of the voltage fluctuation value and the absolute value of the current fluctuation value are calculated at each fourth interval, until the following conditions are simultaneously satisfied: the absolute value of the instantaneous rate of change of voltage and the absolute value of the instantaneous rate of change of current are both less than the second preset rate of change, and the absolute value of the voltage fluctuation value and the absolute value of the current fluctuation value are both less than the second preset fluctuation value, and the time point at this time is defined as the fourth time point; and the third interval is less than the fourth interval.

[0041] The time difference between the fourth time point and the third time point is used as the second preset time.

[0042] In combination with the second aspect, in one implementation, the fourth interval is three times the third interval.

[0043] In a third aspect, the present application provides a battery pack diagnostic device, which includes:

[0044] A setting module, configured to set at least one overcharge level, each overcharge level corresponding to a first voltage threshold and a first capacity threshold;

[0045] An acquisition module is used to obtain the maximum voltage of all cells in the battery pack;

[0046] A judgment module is used to integrate the battery pack current in ampere hours when the above-mentioned maximum voltage is greater than or equal to the second voltage threshold, the absolute value of the battery pack current is less than or equal to the first current threshold, and the duration reaches a first preset time; if the absolute value of the capacity increase obtained by the integration is greater than or equal to the first capacity threshold corresponding to a certain overcharge level, then the battery pack is determined to be overcharged at that overcharge level; the above-mentioned second voltage threshold is less than the first voltage threshold corresponding to any overcharge level; and when the above-mentioned maximum voltage is greater than the first voltage threshold corresponding to any overcharge level, then the battery pack is determined to be overcharged at that overcharge level.

[0047] In a fourth aspect, the present application provides a battery pack diagnostic device, comprising:

[0048] a setting module for setting at least one over-discharge level, each over-discharge level corresponding to a third voltage threshold and a second capacity threshold;

[0049] An acquisition module is used to obtain the minimum voltage of all cells in the battery pack;

[0050] A judgment module is configured to, when the minimum voltage is less than or equal to a fourth voltage threshold, the absolute value of the current of the battery pack is less than or equal to the second current threshold, and the duration reaches a second preset time, perform ampere-hour integration on the battery pack current; if the absolute value of the capacity reduction obtained by the integration is greater than or equal to the second capacity threshold corresponding to a certain over-discharge level, determine that the battery pack is over-discharged at that over-discharge level; when the fourth voltage threshold is greater than the third voltage threshold corresponding to any over-discharge level; and when the minimum voltage is less than the third voltage threshold corresponding to any over-discharge level, determine that the battery pack is over-discharged at that over-discharge level.

[0051] The beneficial effects of the technical solution provided by this application include:

[0052] By setting at least one overcharge level for the battery pack, each overcharge level corresponds to a first voltage threshold and a first capacity threshold, then obtaining the maximum voltage of all cells in the battery pack and making a judgment, when the maximum voltage is greater than or equal to the second voltage threshold, the absolute value of the current of the battery pack is less than or equal to the first current threshold, and the duration reaches a first preset time, the battery pack current is integrated in ampere hours; if the absolute value of the capacity increase obtained by the integration is greater than or equal to the first capacity threshold corresponding to a certain overcharge level, the battery pack is determined to be overcharged at the overcharge level; the second voltage threshold is less than the first voltage threshold corresponding to any overcharge level; when the maximum voltage is greater than the first voltage threshold corresponding to any overcharge level, the battery pack is determined to be overcharged at the overcharge level;

[0053] By setting at least one over-discharge level for the battery pack, each over-discharge level corresponds to a third voltage threshold and a second capacity threshold; obtaining the minimum voltage of all battery cells in the battery pack, and when the minimum voltage is less than or equal to the fourth voltage threshold, the absolute value of the current of the battery pack is less than or equal to the second current threshold, and the duration reaches a second preset time, integrating the battery pack current in ampere hours; if the absolute value of the capacity reduction obtained by the integration is greater than or equal to the second capacity threshold corresponding to a certain over-discharge level, the battery pack is determined to be over-discharged at that over-discharge level; the fourth voltage threshold is greater than the third voltage threshold corresponding to any over-discharge level; when the minimum voltage is less than the third voltage threshold corresponding to any over-discharge level, the battery pack is determined to be over-discharged at that over-discharge level.

[0054] Therefore, combining voltage and capacity to diagnose whether it is overcharged or over-discharged effectively reduces the probability of misjudgment or missed diagnosis, improves the accuracy and reliability of diagnosis, and solves the technical problem of easy misjudgment or missed diagnosis in related technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 Schematic diagram of the flow of a method for diagnosing overcharge and over-discharge of a battery pack in an embodiment of the present application;

[0056] Figure 2 This is a processing flow chart of the battery management system in an embodiment of the present application;

[0057] Figure 3 This is a schematic diagram of the functional modules of an embodiment of the diagnostic device of the present application. DETAILED DESCRIPTION

[0058] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0059] In a first aspect, an embodiment of the present application provides a battery pack overcharge diagnosis method.

[0060] In one embodiment, the battery pack overcharge diagnosis method of the present application includes:

[0061] Setting at least one overcharge level, each overcharge level corresponding to a first voltage threshold and a first capacity threshold;

[0062] Get the maximum voltage of all cells in the battery pack;

[0063] When the above-mentioned maximum voltage is greater than or equal to the second voltage threshold, the absolute value of the current of the battery pack is less than or equal to the first current threshold, and the duration reaches a first preset time, the battery pack current is integrated in ampere-hours; wherein, the second voltage threshold is less than the first voltage threshold corresponding to any overcharge level; if the absolute value of the capacity increase obtained by the integration is greater than or equal to the first capacity threshold corresponding to the overcharge level, it is determined that the battery pack is overcharged at the overcharge level.

[0064] In the above process, when the maximum voltage is greater than the first voltage threshold corresponding to any overcharge level, it is determined that the battery pack is overcharged at the overcharge level.

[0065] If the maximum voltage is greater than or equal to the second voltage threshold and the absolute value of the battery pack current is less than or equal to the first current threshold, and the duration of these conditions reaches a first preset time, then the voltage-based overcharge diagnosis conditions for all overcharge levels are met. If the absolute value of the integrated capacity increase is greater than or equal to the first capacity threshold corresponding to a particular overcharge level, then the capacity-based overcharge diagnosis conditions for that overcharge level are met.

[0066] In this embodiment, at least one overcharge level is set for overcharging the battery pack, each overcharge level corresponds to a first voltage threshold and a first capacity threshold, and then the maximum voltage of all battery cells in the battery pack is obtained and judged. When the maximum voltage is greater than or equal to the second voltage threshold, the absolute value of the current of the battery pack is less than or equal to the first current threshold, and the duration reaches a first preset time, the battery pack current is integrated in ampere hours; if the absolute value of the capacity increase obtained by the integration is greater than or equal to the first capacity threshold corresponding to a certain overcharge level, the battery pack is judged to be overcharged at this overcharge level; the second voltage threshold is less than the first voltage threshold corresponding to any overcharge level; in the above process, when the maximum voltage is greater than the first voltage threshold corresponding to any overcharge level, the battery pack is judged to be overcharged at this overcharge level; therefore, combining voltage and capacity to diagnose whether it is overcharged effectively reduces the probability of misjudgment or missed judgment, improves the accuracy and reliability of diagnosis, and solves the technical problem of easy misjudgment or missed judgment in related technologies.

[0067] On the basis of the above embodiment, in this embodiment, the above-mentioned overcharge levels are provided in multiples, and the first voltage threshold and the first capacity threshold corresponding to the high overcharge level are greater than the first voltage threshold and the first capacity threshold corresponding to the low overcharge level, that is, the first voltage threshold corresponding to the high overcharge level is greater than the first voltage threshold corresponding to the low overcharge level, and the first capacity threshold corresponding to the high overcharge level is greater than the first capacity threshold corresponding to the low overcharge level.

[0068] When determining that the battery pack is overcharged at the overcharge level, the method further includes:

[0069] The highest level among the overcharge levels of the battery pack is obtained to generate a maximum overcharge level signal so that the battery management system can execute a corresponding protection mechanism according to the above maximum overcharge level signal.

[0070] In this embodiment, by setting multiple first voltage thresholds and first capacity thresholds to correspond to multiple overcharge levels, overcharge conditions of different severity can be diagnosed, which facilitates the battery management system to take different countermeasures, thereby protecting the battery pack without completely limiting the battery performance and maximizing the battery performance.

[0071] Preferably, according to the severity of overcharging, in the charging state, the first voltage threshold and the first capacity threshold are respectively set to three, corresponding to three overcharging levels.

[0072] It is understandable that the above-mentioned overcharge levels can be divided into other levels according to actual conditions.

[0073] Furthermore, in one embodiment, when the duration reaches a first preset time, the method further includes:

[0074] First, a first cell capacity of the cell corresponding to the maximum voltage and a second cell capacity corresponding to the first voltage threshold are obtained.

[0075] Then, a first difference between the second battery cell capacity and the first battery cell capacity is obtained, and the first difference or the product of the first difference and the battery health is used as the first capacity threshold.

[0076] Optionally, the first difference is directly used as the first capacity threshold.

[0077] Preferably, the product of the first difference and the battery health is used as the first capacity threshold, and the capacity decay during the use of the battery cell can be taken into account to further increase the judgment accuracy.

[0078] In this embodiment, when the above-mentioned maximum voltage is greater than or equal to the second voltage threshold, the absolute value of the current of the battery pack is less than or equal to the first current threshold, and the duration reaches the first preset time, indicating that the battery cell has reached a stable charging terminal state at this time, the current capacity of the battery cell corresponding to the above-mentioned maximum voltage can be obtained as the first battery cell capacity, which is used to set the first capacity threshold corresponding to the overcharge level, and perform capacity-based diagnosis, and the diagnostic error is small.

[0079] Optionally, the second voltage threshold, the first current threshold, and the first time threshold are set according to a charging performance parameter curve during a cell test. The charging performance parameter curve is a mapping relationship between voltage and current with respect to time during charging.

[0080] Furthermore, in one embodiment, the second voltage threshold is the product of the charge cut-off voltage and a first preset coefficient. Optionally, the first preset coefficient is 0.95-0.99.

[0081] Optionally, the first voltage threshold is slightly greater than the charging cut-off voltage.

[0082] Optionally, before obtaining the maximum voltage of all cells in the battery pack, the method further includes obtaining a first preset time, which is obtained based on the second voltage threshold and the first current threshold.

[0083] Based on the above embodiment, in this embodiment, obtaining the first preset time specifically includes:

[0084] First, the second voltage threshold and the first current threshold are set according to the charging performance parameter curve during the battery cell test.

[0085] Then, the time point when the voltage is first greater than or equal to the second voltage threshold and the absolute value of the current is less than or equal to the first current threshold in the above-mentioned charging performance parameter curve is taken as the first time point A1. Subsequently, the absolute value of the instantaneous change rate of voltage and the absolute value of the instantaneous change rate of current are calculated at each first interval time, and the absolute value of the voltage fluctuation value and the absolute value of the current fluctuation value are calculated at each second interval time, until the following conditions are simultaneously satisfied: the calculated absolute value of the instantaneous change rate of voltage and the absolute value of the instantaneous change rate of current are both less than the first preset change rate, and the calculated absolute value of the voltage fluctuation value and the absolute value of the current fluctuation value are both less than the first preset fluctuation value, and the time point at this time is taken as the second time point A2, and the time difference between A2 and A1 is taken as the first preset time.

[0086] Optionally, the first interval time is smaller than the second interval time.

[0087] Preferably, the second interval time is three times the first interval time.

[0088] In this embodiment, by setting the first preset time, a current and voltage filtering function is achieved to ensure that the charging terminal state is reached.

[0089] Specifically, when the battery pack is charging, the cell voltage with the valid and maximum voltage value is read in real time as the maximum voltage. During the entire overcharge diagnosis process, if one of the following two conditions is met, the battery pack is determined to be overcharged at a certain overcharge level:

[0090] (1) The maximum voltage is greater than the first voltage threshold corresponding to the overcharge level;

[0091] (2) The voltage-based overcharge diagnosis conditions and the capacity-based overcharge diagnosis conditions are met in sequence.

[0092] Condition (1) considers the case of cell voltage overcharge; condition (2) combines capacity and voltage to diagnose overcharge, considering the possibility of voltage overcharge. This condition considers the case of capacity overcharge. Therefore, for a certain overcharge level, only one of conditions (1) and (2) must be met first for the battery pack to be overcharged at that level.

[0093] Among them, condition (2) needs to satisfy the voltage-based overcharge diagnosis condition and the capacity-based overcharge diagnosis condition in sequence. The voltage-based overcharge diagnosis condition is: the maximum voltage is greater than or equal to the second voltage threshold, and the absolute value of the current of the battery pack is less than or equal to the first current threshold, and the above situation lasts for a first preset time.

[0094] After the voltage-based overcharge diagnosis conditions are met, capacity-based overcharge diagnosis is performed. The capacity-based overcharge diagnosis conditions are as follows: from the moment the voltage-based overcharge diagnosis conditions are met, the battery pack current is integrated in ampere-hours. If the absolute value of the integrated capacity increase is greater than or equal to the first capacity threshold of the corresponding overcharge level, the capacity-based overcharge diagnosis conditions for that overcharge level are also met.

[0095] At this time, condition (2) is met, and the battery pack is determined to be overcharged at this overcharge level.

[0096] In summary, when an overcharge abnormality is diagnosed, the highest overcharge level among all levels is taken and a signal of the highest overcharge level generated is sent to the battery management system. Upon receiving this signal, the battery management system can implement corresponding overcharge protection measures according to the preset process and protection mechanism.

[0097] In one embodiment, based on the voltage signal collected by the sampling line of each battery cell in the battery pack, the battery cell with the valid voltage and the maximum voltage value is determined in real time. The maximum voltage is recorded as V max .

[0098] It can be understood that the charge cut-off voltage refers to the cell voltage when the battery reaches a fully charged state during the specified constant current charging period. Selecting an appropriate charge cut-off voltage can effectively increase the life of the battery pack. The charge cut-off voltage is an important parameter in the battery charging process. Its setting needs to comprehensively consider the battery's performance, life and safety. The charge cut-off voltage is recorded as V r0 .

[0099] According to the severity of overcharge, the overcharge level is divided into level 1, level 2 and level 3. The diagnostic conditions and diagnostic thresholds corresponding to each overcharge level are shown in Table 1.

[0100] When the voltage and capacity overcharge diagnosis or voltage overcharge threshold diagnosis conditions for a certain overcharge level are met, the overcharge level is determined to be established. The voltage and capacity overcharge diagnosis conditions must meet conditions A and B in sequence.

[0101] Table 1 Overcharge diagnosis conditions

[0102]

[0103] Taking overcharge level 1 as an example, the voltage and capacity overcharge diagnosis conditions need to be met in sequence when conditions A and B are met. Condition A needs (1) and (2) to be met at the same time and continuously. t r0 time.

[0104] In condition A, the first preset coefficient is less than 1. Optionally, The reference value range can be 0.95~0.99. The smaller it is, the easier it is to satisfy condition A (1). It is a calibration value determined by comprehensively considering the performance parameters of the battery cell and the test conditions of the battery cell during application.

[0105] The absolute value of the current is used to compare with the current threshold.

[0106] At the end of charging, that is, when the battery is close to being fully charged, it will enter the constant voltage charging stage. At this time, the charging current will gradually decrease until it reaches a lower stable current value, indicating that the charging process is about to end. This lower stable current value can be regarded as the charging cut-off current. It is the current threshold during charging, which is the absolute value of a calibration value determined by comprehensively considering the performance parameters of the battery cell and the test conditions of the battery cell during application. It is generally slightly larger than the absolute value of the charge cut-off current. The larger is , the easier it is to satisfy condition (2) in A. Alternatively, It is 0.01C~0.2C (not limited to this range, C is the battery rate, which refers to the current value required for the battery to be fully charged to its rated capacity within a specified time).

[0107] t r0 It is the preset duration that satisfies both (1) and (2) in conditions A. It is a calibration value determined by comprehensively considering the performance parameters of the battery cell and the test conditions of the battery cell during application. t r0 The smaller is , the sooner condition A is satisfied. Optionally, t r0 It is 3s~10s. It is understandable that tr0 It is not limited to the above range.

[0108] In summary, 、 and t r0 They jointly determine the moment when condition A is met, that is, the moment when the ampere-hour integration of the current begins, so that condition B can be effectively judged.

[0109] Similarly, as shown in Table 1, the overcharge levels 1, 2, and 3 have the same condition A when performing voltage and capacity overcharge diagnosis, that is, the second voltage threshold, first current threshold, and preset time when performing condition A judgment are all the same.

[0110] From the moment when condition A is met, the absolute value of the battery pack capacity increase is calculated in real time using the ampere-hour integral. The calculation formula for the ampere-hour integral is:

[0111]

[0112] in, It is from the moment when the overcharge level 1 condition A is met ( ) The time when the timing starts.

[0113] Based on the real-time integration results, determine whether the overcharge level 1 condition B is met as follows:

[0114]

[0115] Among them, SOH is the battery health. It is the first difference used to determine the first capacity threshold, which needs to take into account the performance parameters of the battery cell and the actual application of the battery cell. In addition to being related to the performance parameters such as the rated capacity of the battery cell, this value is also related to the threshold set in condition A. That is, the stricter the threshold in condition A is set (the more difficult condition A is to meet), the corresponding When the overcharge level 1 condition B is also met, the voltage and capacity overcharge diagnosis conditions of overcharge level 1 are met. At this time, the battery is diagnosed as having an overcharge level 1 fault.

[0116] In this embodiment, considering the fluctuation of voltage and current, a time is added t r0 Redundant judgment is made to effectively filter the influence of voltage or current fluctuations, that is, to achieve a truly stable charging terminal state before performing ampere-hour integration to reduce the error in subsequent capacity judgment.

[0117] Among them, when the stable charging terminal state is truly reached, the current cell capacity level, that is, the first cell capacity, is , and the cell capacity level corresponding to the first voltage threshold, that is, the second cell capacity, is , then and The difference, as Taking into account the capacity attenuation during the use of the battery, Multiplied by SOH to obtain the first capacity threshold.

[0118] Similarly, according to Table 1, the corresponding conditions B for overcharge level 2 and level 3 are and The same acquisition method is used. In this embodiment, When determining the voltage and capacity overcharge diagnostic conditions for overcharge level 1, the voltage and capacity overcharge diagnostic conditions for overcharge levels 2 and 3 are also determined simultaneously based on the corresponding conditions in Table 1.

[0119] During the entire charging process, if one of the following conditions is met, the battery pack is judged to be overcharged at level 1:

[0120] (1) Overcharge level 1 corresponds to the voltage and capacity overcharge diagnosis conditions A and B being met in sequence;

[0121] (2) The voltage overcharge threshold diagnostic conditions corresponding to overcharge level 1 meet the following requirements:

[0122] in, It is a calibration value determined by considering the performance parameters of the battery cell and the test conditions of the battery cell during application. Similarly, according to Table 1, the judgment of overcharge level 2 and level 3 is performed at the same time. Among them, the voltage threshold diagnosis conditions of overcharge level 2 and level 3 are and It is also a calibration value determined by comprehensively considering the performance parameters of the battery cell and the test conditions of the battery cell during application. In this embodiment, the first voltage threshold is greater than the charging cut-off voltage. Therefore, it satisfies: .

[0123] When overcharge is diagnosed, the highest overcharge level is taken and a signal is sent to the battery management system. Upon receiving this signal, the battery management system responds according to its pre-set workflow and protection mechanisms, implementing appropriate overcharge protection measures. For example, charging power may be limited, the charging circuit may be immediately disconnected, a fault indicator may be illuminated, or the equalization function may be enabled.

[0124] In a second aspect, an embodiment of the present application also provides a battery pack over-discharge diagnosis method.

[0125] In one embodiment, the battery pack over-discharge diagnosis method of the present application includes:

[0126] Setting at least one over-discharge level, each over-discharge level corresponding to a third voltage threshold and a second capacity threshold;

[0127] Get the minimum voltage of all cells in the battery pack;

[0128] When the above-mentioned minimum voltage is less than or equal to the fourth voltage threshold, the absolute value of the current of the battery pack is less than or equal to the second current threshold, and the duration reaches the second preset time, the battery pack current is integrated in ampere-hours; wherein the fourth voltage threshold is greater than the third voltage threshold corresponding to any over-discharge level; if the absolute value of the capacity reduction obtained by the integration is greater than or equal to the second capacity threshold corresponding to a certain over-discharge level, the battery pack is determined to be over-discharged at that over-discharge level.

[0129] In the above process, when the above minimum voltage is less than the third voltage threshold corresponding to any over-discharge level, it is determined that the battery pack is over-discharged at that level.

[0130] If the minimum voltage is less than or equal to a fourth voltage threshold and the absolute value of the battery pack current is less than or equal to a second current threshold, and if these conditions are met for a second predetermined period of time, then the voltage-based over-discharge diagnostic conditions for all over-discharge levels are met. If the absolute value of the integrated capacity reduction is greater than or equal to the second capacity threshold corresponding to the first over-discharge level, then the capacity-based over-discharge diagnostic conditions for the first over-discharge level are met.

[0131] In this embodiment, at least one over-discharge level is set for the battery pack, with each over-discharge level corresponding to a third voltage threshold and a second capacity threshold. The minimum voltage of all cells in the battery pack is obtained. When the minimum voltage is less than or equal to the fourth voltage threshold, the absolute value of the battery pack current is less than or equal to the second current threshold, and the duration reaches a second preset time, the battery pack current is integrated in ampere-hours. If the absolute value of the capacity reduction obtained by the integration is greater than or equal to the second capacity threshold corresponding to a certain over-discharge level, the battery pack is determined to be over-discharged at that over-discharge level. The fourth voltage threshold is greater than the third voltage threshold corresponding to any over-discharge level. In the above process, when the minimum voltage is less than the third voltage threshold corresponding to any over-discharge level, the battery pack is determined to be over-discharged at that over-discharge level. Therefore, combining voltage and capacity to diagnose over-discharge effectively reduces the probability of misjudgment or missed diagnosis, improves the accuracy and reliability of diagnosis, and solves the technical problem of easy misjudgment or missed diagnosis existing in related technologies.

[0132] Based on the above embodiment, in this embodiment, there are multiple over-discharge levels, and the third voltage threshold corresponding to the high over-discharge level is smaller than the third voltage threshold corresponding to the low over-discharge level, and the second capacity threshold corresponding to the high over-discharge level is larger than the second capacity threshold corresponding to the low over-discharge level.

[0133] When determining that the battery pack is over-discharged at the over-discharge level, the following steps are also included:

[0134] The highest over-discharge level among the over-discharge levels of the battery pack is obtained to generate a maximum over-discharge level signal so that the battery management system can execute a corresponding protection mechanism according to the above maximum over-discharge level signal.

[0135] In this embodiment, by setting multiple third voltage thresholds and second capacity thresholds to correspond to multiple over-discharge levels, over-discharge conditions of different severity can be diagnosed, which facilitates the battery management system to take different countermeasures, thereby protecting the battery pack without completely limiting the battery performance and maximizing the battery performance.

[0136] Preferably, according to the severity of over-discharge, in the case of discharge, the third voltage threshold and the second capacity threshold are respectively set to three, corresponding to three over-discharge levels.

[0137] It is understandable that the above-mentioned over-discharge levels can be further divided into other levels according to actual conditions.

[0138] Furthermore, in one embodiment, when the duration reaches the second preset time, the method further includes:

[0139] First, the third cell capacity of the cell corresponding to the minimum voltage and the fourth cell capacity corresponding to the third voltage threshold are obtained.

[0140] Then, a second difference between the third battery cell capacity and the fourth battery cell capacity is obtained, and the second difference or the product of the second difference and the battery health is used as the second capacity threshold.

[0141] Optionally, the second difference is directly used as the second capacity threshold.

[0142] Preferably, the product of the second difference and the battery health is used as the second capacity threshold, and the capacity decay during the use of the battery cell can be taken into account to further increase the judgment accuracy.

[0143] In this embodiment, when the above-mentioned minimum voltage is less than or equal to the fourth voltage threshold, the absolute value of the current of the battery pack is less than or equal to the second current threshold, and the duration reaches the second preset time, indicating that the battery cell has reached a stable end-of-discharge state, the current capacity of the battery cell corresponding to the above-mentioned minimum voltage can be obtained as the third battery cell capacity, which is used to set the second capacity threshold and perform capacity-based diagnosis, and the diagnostic error is small.

[0144] Optionally, the fourth voltage threshold, the second current threshold, and the second time threshold are set according to a discharge performance parameter curve during a cell test. The discharge performance parameter curve is a mapping relationship between voltage and current with respect to time during discharge.

[0145] Furthermore, in one embodiment, the fourth voltage threshold is the product of the discharge cut-off voltage and a second preset coefficient. Optionally, the second preset coefficient is 1.01-1.03.

[0146] Optionally, in one embodiment, before obtaining the minimum voltage of all cells in the battery pack, the method further includes obtaining a second preset time, which is obtained based on the fourth voltage threshold and the second current threshold.

[0147] Based on the above embodiment, in this embodiment, obtaining the second preset time specifically includes:

[0148] First, the fourth voltage threshold and the second current threshold are set according to the discharge performance parameter curve during the battery cell test.

[0149] Then, the time point in the above-mentioned discharge performance parameter curve when the voltage reaches less than or equal to the fourth voltage threshold and the absolute value of the current is less than or equal to the third current threshold for the first time is taken as the third time point B1. Subsequently, the absolute value of the instantaneous change rate of voltage and the absolute value of the instantaneous change rate of current are calculated at every third interval, and the absolute value of the voltage fluctuation value and the absolute value of the current fluctuation value are calculated at every fourth interval, until the following conditions are simultaneously satisfied: the calculated absolute value of the instantaneous change rate of voltage and the absolute value of the instantaneous change rate of current are both less than the second preset change rate, and the calculated absolute value of the voltage fluctuation value and the absolute value of the current fluctuation value are both less than the second preset fluctuation value, and the time point at this time is taken as the fourth time point B2, and the time difference between B2 and B1 is taken as the second preset time.

[0150] Optionally, the third interval time is shorter than the fourth interval time.

[0151] Preferably, the fourth interval time is three times the third interval time.

[0152] In this embodiment, by setting the second preset time, a current and voltage filtering function is achieved to ensure that the discharge end state is reached.

[0153] Specifically, when the battery pack is discharging, the voltage of the cell with the minimum voltage is read in real time as the minimum voltage. During the entire over-discharge diagnosis process, if one of the following two conditions is met, the battery pack is determined to be over-discharged at a certain over-discharge level:

[0154] (1) The minimum voltage is less than the third voltage threshold corresponding to the over-discharge level;

[0155] (2) The voltage-based over-discharge diagnosis conditions and the capacity-based over-discharge diagnosis conditions are met in sequence.

[0156] Condition (1) considers voltage overdischarge; condition (2) considers the possibility of voltage overdischarge and combines capacity and voltage to diagnose overdischarge. This condition considers capacity overdischarge. Therefore, for a given overdischarge level, only one of conditions (1) and (2) must be met first for the battery pack to be considered overdischarged at that level.

[0157] Among them, condition (2) must satisfy the voltage-based over-discharge diagnosis condition and the capacity-based over-discharge diagnosis condition in sequence. The voltage-based over-discharge diagnosis condition is: the minimum voltage is less than or equal to the fourth voltage threshold, and the absolute value of the battery pack current is less than or equal to the second current threshold, and the above situation lasts for a second preset time.

[0158] When the voltage-based over-discharge diagnosis conditions are met, capacity-based over-discharge diagnosis is performed. The capacity-based over-discharge diagnosis conditions are as follows: starting from the moment the voltage-based over-discharge diagnosis conditions are met, the battery pack current is integrated in ampere-hours. If the integrated capacity reduction value is greater than or equal to the second capacity threshold corresponding to the over-discharge level, the capacity-based over-discharge diagnosis conditions for that over-discharge level are also met.

[0159] At this time, condition (2) is met, and the battery pack is determined to be over-discharged at this over-discharge level.

[0160] In summary, when an over-discharge abnormality is diagnosed, the highest over-discharge level among all levels is taken and a signal of the highest over-discharge level generated is sent to the battery management system. Upon receiving this signal, the battery management system can implement corresponding over-discharge protection measures according to the preset process and protection mechanism.

[0161] In one embodiment, based on the voltage signal collected by the sampling line of each battery cell in the battery pack, the battery cell with the valid voltage and the minimum voltage value is determined in real time. The minimum voltage is recorded as V min .

[0162] It can be understood that the discharge cut-off voltage refers to the voltage value at which the discharge of the battery pack cells needs to be stopped when the voltage drops to a certain level during the discharge process. By setting it reasonably, it can ensure that the cells work within a safe range, avoid damage to the battery pack caused by excessive discharge, thereby extending the service life of the battery pack and helping to improve the safety of the battery pack. The discharge cut-off voltage is recorded as V d0 .

[0163] According to the severity of overdischarge, the overdischarge levels are divided into level 1, level 2, and level 3. The diagnostic conditions and diagnostic thresholds corresponding to each overdischarge level are shown in Table 2.

[0164] When the voltage and capacity over-discharge diagnosis or voltage over-discharge threshold diagnosis conditions for a certain over-discharge level are met, the over-discharge level is determined to be established. The voltage and capacity over-discharge diagnosis conditions must meet conditions C and D in sequence.

[0165] Table 2 Over-discharge diagnosis conditions

[0166]

[0167] Taking over-discharge level 1 as an example, the voltage and capacity over-discharge diagnostic conditions require that conditions C and D are met in sequence. Condition C requires (1) and (2) to be met at the same time and continuously. t d0 time.

[0168] In condition C, the second preset coefficient is greater than 1. Optionally, The reference value range can be 1.01~1.05. The larger is, the easier it is to satisfy condition C (1). It is a calibration value determined by comprehensively considering the performance parameters of the battery cell and the test conditions of the battery cell during application.

[0169] At the end of discharge, when the voltage drops to close to the discharge cut-off voltage, the discharge current will gradually decrease and reach a lower stable current value. This lower stable current value can be regarded as the discharge cut-off current. It is the current threshold during discharge, which is the absolute value of a calibration value determined by comprehensively considering the performance parameters of the battery cell and the test conditions of the battery cell during application. It is generally slightly larger than the absolute value of the discharge cut-off current. The larger is , the easier it is to satisfy condition (2) in C. Alternatively, 0.01C~0.2C (not limited to this range).

[0170] t d0 It is the preset duration that satisfies both (1) and (2) in conditions C. It is a calibration value determined by comprehensively considering the performance parameters of the battery cell and the test conditions of the battery cell during application. t d0 The smaller is, the earlier condition C is satisfied. Optionally, t d0 3s~10s.

[0171] In summary, 、 and t d0 They jointly determine the moment when condition C is met, that is, the moment when the ampere-hour integration of the current begins, so that condition D can be effectively judged.

[0172] Similarly, as shown in Table 2, the voltage and capacity over-discharge diagnosis conditions for levels 1, 2, and 3 are the same under Condition C, that is, the fourth voltage threshold, the second current threshold, and the preset time for the judgment under Condition C are all the same.

[0173] From the moment when condition C is met, the absolute value of the capacity reduction of the battery pack is calculated in real time using the ampere-hour integral. The calculation formula for the ampere-hour integral is:

[0174]

[0175] in, It is the moment when the condition C of over discharge level 1 is satisfied ( =0) to start timing.

[0176] Based on the real-time integration results, the following judgment is made on whether the over-discharge level 1 condition D is met:

[0177]

[0178] Among them, SOH is the battery health. It is the second difference used to obtain the second capacity threshold, which needs to take into account the performance parameters of the battery cell and the actual application of the battery cell. In addition to being related to the performance parameters such as the rated capacity of the battery cell, this value is also related to the threshold set in condition C. That is, the stricter the threshold in condition C is set (the more difficult it is to meet condition C), the corresponding When the over-discharge level 1 condition D is also met, the voltage and capacity over-discharge diagnosis conditions of over-discharge level 1 are met. At this time, the battery is diagnosed as having an over-discharge level 1 fault.

[0179] In this embodiment, considering the fluctuation of voltage and current, a time is added t d0 Redundant judgment is made to effectively filter the influence of voltage or current fluctuations, that is, to achieve a truly stable discharge end state before performing ampere-hour integration to reduce the error in subsequent capacity judgment.

[0180] Among them, when the stable end-of-discharge state is truly reached, the current cell capacity level, that is, the third cell capacity, is , and the cell capacity level corresponding to the third voltage threshold, i.e., the fourth cell capacity, is , then and The difference, as Taking into account the capacity attenuation during the use of the battery, Multiplied by SOH to form the second capacity threshold.

[0181] Similarly, according to Table 2, the corresponding conditions D for over-discharge level 2 and level 3 are and The same acquisition method is used. In this embodiment, When determining the voltage and capacity over-discharge diagnostic conditions for over-discharge level 1, the voltage and capacity over-discharge diagnostic conditions for over-discharge levels 2 and 3 are also determined based on the corresponding conditions in Table 2.

[0182] During the entire discharge process, if any of the following conditions is met, the battery pack is judged to be in over-discharge level 1:

[0183] (1) Over-discharge level 1 corresponds to voltage and capacity over-discharge diagnosis, and conditions C and D are met in sequence;

[0184] (2) The voltage threshold diagnostic conditions corresponding to over-discharge level 1 are met:

[0185] in, It is a calibration value determined by considering the performance parameters of the battery cell and the test conditions of the battery cell during application. Similarly, according to Table 2, over-discharge level 2 and level 3 are diagnosed at the same time. Among them, the voltage threshold diagnosis conditions of over-discharge level 2 and level 3 are and It is also a calibration value determined by comprehensively considering the performance parameters of the battery cell and the test conditions of the battery cell during application. In this embodiment, the third voltage threshold is less than the discharge cut-off voltage. Therefore, it satisfies: .

[0186] When over-discharge is diagnosed, the highest over-discharge level is taken and sent to the battery management system. Upon receiving this highest over-discharge level signal, the battery management system responds according to its preset workflow and protection mechanisms, executing appropriate over-discharge protection measures. For example, discharge power limitation, immediate disconnection of the discharge circuit, illumination of the fault indicator, or activation of the limit balancing function may be implemented.

[0187] Alternatively, as Figure 1 As shown, this embodiment also provides a method for diagnosing battery pack overcharge and overdischarge, which specifically includes:

[0188] A1. Determine whether the current state is charging. If so, proceed to A2; otherwise, proceed to A7.

[0189] A2. Get the maximum voltage and go to A3 and A4.

[0190] A3. Perform voltage and capacity overcharge diagnosis and proceed to A5.

[0191] A4. Perform voltage overcharge threshold diagnosis;

[0192] A5. Determine whether the voltage and capacity overcharge diagnostic conditions or the voltage overcharge threshold diagnostic conditions are met. If so, proceed to A6; otherwise, proceed to A1.

[0193] A6. Determine overcharge.

[0194] A7. Determine whether the current state is a discharge state. If so, proceed to A8. Otherwise, end.

[0195] A8. Get the minimum voltage and go to A9 and A10.

[0196] A9. Perform voltage and capacity over-discharge diagnosis and proceed to A11.

[0197] A10. Perform voltage over-discharge threshold diagnosis.

[0198] A11. Determine whether the voltage and capacity over-discharge diagnostic conditions or the voltage over-discharge threshold diagnostic conditions are met. If so, proceed to A12; otherwise, proceed to A7.

[0199] A12. Determined to be over-discharged.

[0200] In this embodiment, the battery pack is generally composed of multiple battery cells. For each battery cell, a sampling circuit for detecting the battery cell voltage is arranged inside the battery pack, which can read the voltage value of each battery cell in real time; a sampling circuit for detecting the battery pack current is also arranged, which can read the collected battery pack current value in real time.

[0201] In both charging and discharging conditions, overcharging and overdischarging are divided into three levels according to the severity of the battery pack overcharging and overdischarging. Each level performs diagnostic judgments on two conditions, and each level has a corresponding threshold.

[0202] Further, if Figure 2 As shown in the figure, the battery management system processes the overcharge and over-discharge diagnosis results as follows:

[0203] B1. Determine whether the device is in charging condition. If so, proceed to B2; otherwise, proceed to B3.

[0204] B2. Determine whether the highest overcharge level signal is received. If so, proceed to B5; otherwise, proceed to B1.

[0205] B3. Determine whether it is a discharge condition. If so, go to B4; otherwise, end.

[0206] B4. Determine whether the highest over-discharge level signal has been received. If so, proceed to B5; otherwise, proceed to B3.

[0207] B5. Execute the corresponding workflow and protection mechanism based on the received level signal.

[0208] In this embodiment, the battery management system can implement corresponding protection measures based on the overcharge or over-discharge abnormalities diagnosed in advance to ensure the safety of the battery pack. Depending on the different levels of overcharge or over-discharge, the protection mechanism of the battery management system includes:

[0209] (1) Limit the charge and discharge power or immediately disconnect the charge and discharge circuit;

[0210] (2) Limit the equalization function to be turned on;

[0211] (3) Prohibit normal use of heating or cooling functions;

[0212] (4) Turn on the fault light;

[0213] (5) Notify the system or user of the alarm information;

[0214] (6) Record the relevant data of this overcharge / overdischarge event;

[0215] (7) Upload fault level.

[0216] In some embodiments, since the current at the end of charge and discharge is relatively small, it is possible that although the voltage of the battery cell has not reached the voltage threshold of overcharge or over-discharge, the increase or decrease in its capacity exceeds the corresponding limit, causing the battery pack to have a capacity overcharge or over-discharge failure, which will also affect the performance and life of the battery pack.

[0217] In this embodiment, real-time monitoring of voltage and capacity changes is used to accurately diagnose battery pack overcharge and over-discharge. Capacity protection is added to voltage protection, taking into account both voltage and capacity overcharge or over-discharge anomalies. This allows for a better understanding of the extent of charge and discharge, improving diagnostic accuracy. Furthermore, by setting different levels, overcharge and over-discharge severity can be diagnosed, allowing the BMS to take different countermeasures, protecting the battery pack without limiting battery performance.

[0218] In a third aspect, the present application also provides a battery pack diagnostic device, such as Figure 3 As shown, the above device includes a setting module, an acquisition module and a judgment module.

[0219] The setting module is used to set at least one overcharge level, and each overcharge level corresponds to a first voltage threshold and a first capacity threshold.

[0220] The above acquisition module is used to obtain the maximum voltage of all cells in the battery pack.

[0221] The above-mentioned judgment module is used to integrate the battery pack current in ampere hours when the above-mentioned maximum voltage is greater than or equal to the second voltage threshold, the absolute value of the current of the battery pack is less than or equal to the first current threshold, and the duration reaches a first preset time; if the absolute value of the capacity increase obtained by the integration is greater than or equal to the first capacity threshold corresponding to a certain overcharge level, it is determined that the battery pack is overcharged at the overcharge level, and the above-mentioned second voltage threshold is less than the first voltage threshold corresponding to any overcharge level; and when the above-mentioned maximum voltage is greater than the first voltage threshold corresponding to any overcharge level, it is determined that the battery pack is overcharged at the overcharge level.

[0222] Furthermore, in one embodiment, there are multiple overcharge levels, and the first voltage threshold and the first capacity threshold corresponding to the high overcharge level are greater than the first voltage threshold and the first capacity threshold corresponding to the low overcharge level;

[0223] When the judgment module determines that the battery pack is overcharged at the overcharge level, it is further used to:

[0224] The highest level among the overcharge levels of the battery pack is obtained to generate a maximum overcharge level signal so that the battery management system can execute a corresponding protection mechanism according to the above maximum overcharge level signal.

[0225] Furthermore, in one embodiment, the setting module is further configured to: when the duration reaches a first preset time, obtain a first cell capacity of the cell corresponding to the maximum voltage and a second cell capacity corresponding to the first voltage threshold;

[0226] A first difference between the second battery cell capacity and the first battery cell capacity is obtained, and the first difference or the product of the first difference and the battery health is used as the first capacity threshold.

[0227] Furthermore, in one embodiment, the second voltage threshold is: the product of the charging cut-off voltage and the first preset coefficient;

[0228] Furthermore, in one embodiment, the acquisition module is further configured to acquire a first preset time before acquiring the maximum voltage of all cells in the battery pack; the first preset time is obtained based on the second voltage threshold and the first current threshold.

[0229] Furthermore, in one embodiment, the acquisition module is further configured to:

[0230] Setting the second voltage threshold and the first current threshold according to the charging performance parameter curve during the battery cell test;

[0231] The time point at which the voltage is greater than or equal to the second voltage threshold and the absolute value of the current is less than or equal to the first current threshold in the above charging performance parameter curve is the first time point;

[0232] Calculating the absolute value of the instantaneous rate of change of voltage and the absolute value of the instantaneous rate of change of current at each first interval, and calculating the absolute value of the voltage fluctuation value and the absolute value of the current fluctuation value at each second interval, until simultaneously satisfying: the absolute value of the instantaneous rate of change of voltage and the absolute value of the instantaneous rate of change of current are both less than the first preset rate of change, and the absolute value of the voltage fluctuation value and the absolute value of the current fluctuation value are both less than the first preset fluctuation value, and the time point at this time is regarded as the second time point; and the first interval is less than the second interval;

[0233] The time difference between the second time point and the first time point is used as the first preset time.

[0234] Furthermore, the second interval time is three times the first interval time.

[0235] In a fourth aspect, an embodiment of the present application further provides a battery pack diagnostic device, which includes a setting module, an acquisition module and a judgment module.

[0236] The setting module is used to set at least one over-discharge level, and each over-discharge level corresponds to a third voltage threshold and a second capacity threshold.

[0237] The above acquisition module is used to obtain the minimum voltage of all cells in the battery pack.

[0238] The above-mentioned judgment module is used to integrate the battery pack current in ampere hours when the above-mentioned minimum voltage is less than or equal to the fourth voltage threshold, the absolute value of the battery pack current is less than or equal to the second current threshold, and the duration reaches the second preset time; if the absolute value of the capacity reduction obtained by the integration is greater than or equal to the second capacity threshold corresponding to a certain over-discharge level, then it is determined that the battery pack is over-discharged at the over-discharge level, and the above-mentioned fourth voltage threshold is greater than the third voltage threshold corresponding to any over-discharge level; and when the above-mentioned minimum voltage is less than the third voltage threshold corresponding to any over-discharge level, then it is determined that the battery pack is over-discharged at the over-discharge level.

[0239] Furthermore, in one embodiment, there are multiple over-discharge levels, and the third voltage threshold corresponding to the high over-discharge level is smaller than the third voltage threshold corresponding to the low over-discharge level, and the second capacity threshold corresponding to the high over-discharge level is larger than the second capacity threshold corresponding to the low over-discharge level;

[0240] When the judgment module determines that the battery pack is over-discharged at the over-discharge level, it is further configured to:

[0241] The highest over-discharge level among the over-discharge levels of the battery pack is obtained to generate a maximum over-discharge level signal so that the battery management system can execute a corresponding protection mechanism according to the above maximum over-discharge level signal.

[0242] Furthermore, in one embodiment, the setting module is further configured to: when the duration reaches a second preset time, obtain a third cell capacity of the cell corresponding to the minimum voltage and a fourth cell capacity corresponding to the third voltage threshold;

[0243] A second difference between the third cell capacity and the fourth cell capacity is obtained, and the second difference or the product of the second difference and the battery health is used as the second capacity threshold.

[0244] Furthermore, in one embodiment, the fourth voltage threshold is: the product of the discharge cut-off voltage and the second preset coefficient;

[0245] Furthermore, in one embodiment, the acquisition module is further configured to acquire a second preset time before acquiring the minimum voltage of all cells in the battery pack; the second preset time is obtained based on the fourth voltage threshold and the second current threshold.

[0246] Furthermore, in one embodiment, the acquisition module is further configured to:

[0247] Setting the fourth voltage threshold and the second current threshold according to the discharge performance parameter curve during the battery cell test;

[0248] The time point at which the voltage reaches or is equal to the fourth voltage threshold for the first time and the absolute value of the current is equal to or less than the third current threshold in the above-mentioned discharge performance parameter curve is referred to as the third time point;

[0249] The absolute value of the instantaneous rate of change of voltage and the absolute value of the instantaneous rate of change of current are calculated at each third interval, and the absolute value of the voltage fluctuation value and the absolute value of the current fluctuation value are calculated at each fourth interval, until the following conditions are simultaneously satisfied: the absolute value of the instantaneous rate of change of voltage and the absolute value of the instantaneous rate of change of current are both less than the second preset rate of change, and the absolute value of the voltage fluctuation value and the absolute value of the current fluctuation value are both less than the second preset fluctuation value, and the time point at this time is defined as the fourth time point; and the third interval is less than the fourth interval.

[0250] The time difference between the fourth time point and the third time point is used as the second preset time.

[0251] Furthermore, the fourth interval is three times the third interval.

[0252] In other embodiments, the above-mentioned device includes a setting module, an acquisition module and a judgment module.

[0253] The setting module is used to set at least one overcharge level, each overcharge level corresponds to a first voltage threshold and a first capacity threshold, and to set at least one overdischarge level, each overdischarge level corresponds to a third voltage threshold and a second capacity threshold.

[0254] The acquisition module is used to obtain the maximum voltage of all cells in the battery pack under charging conditions; and to obtain the minimum voltage of all cells in the battery pack under discharging conditions.

[0255] The above-mentioned judgment module is used to integrate the battery pack current in ampere hours when the above-mentioned maximum voltage is greater than or equal to the second voltage threshold, the absolute value of the battery pack current is less than or equal to the first current threshold, and the duration reaches a first preset time; if the absolute value of the capacity increase obtained by the integration is greater than or equal to the first capacity threshold corresponding to a certain overcharge level, then it is determined that the battery pack is overcharged at that overcharge level, and the above-mentioned second voltage threshold is less than the first voltage threshold corresponding to any overcharge level; and when the above-mentioned maximum voltage is greater than the first voltage threshold corresponding to any overcharge level, then it is determined that the battery pack is overcharged at that overcharge level; it is also used to integrate the battery pack current in ampere hours when the above-mentioned minimum voltage is less than or equal to the fourth voltage threshold, the absolute value of the battery pack current is less than or equal to the second current threshold, and the duration reaches a second preset time; if the absolute value of the capacity decrease obtained by the integration is greater than or equal to the second capacity threshold corresponding to a certain over-discharge level, then it is determined that the battery pack is over-discharged at that over-discharge level, and the above-mentioned fourth voltage threshold is greater than the third voltage threshold corresponding to any over-discharge level; and when the above-mentioned minimum voltage is less than the third voltage threshold corresponding to any over-discharge level, then it is determined that the battery pack is over-discharged at that over-discharge level.

[0256] Among them, the functional implementation of each module in the above-mentioned device corresponds to each step in the above-mentioned diagnosis method embodiment, and its functions and implementation processes are no longer described here one by one.

[0257] It should be noted that the serial numbers of the above-mentioned embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments.

[0258] The terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices. The terms "first", "second" and "third" are used to distinguish different objects, etc., and do not represent a sequence, nor do they limit the "first", "second" and "third" to different types.

[0259] In some processes described in the embodiments of the present application, multiple operations or steps are included in a specific order. However, it should be understood that these operations or steps may not be performed in the order in which they appear in the embodiments of the present application or may be performed in parallel. The sequence numbers of the operations are only used to distinguish different operations, and the sequence numbers themselves do not represent any execution order. In addition, these processes may include more or fewer operations, and these operations or steps may be performed in sequence or in parallel, and these operations or steps may be combined.

[0260] Through the description of the above embodiments, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus the necessary general hardware platform. Of course, they can also be implemented by hardware, but in many cases the former is a better embodiment. Based on this understanding, the technical solution of this application, or the part that contributes to the existing technology, can be embodied in the form of a software product. This computer software product is stored in the storage medium (such as ROM / RAM, magnetic disk, optical disk) as described above and includes a number of instructions for enabling a terminal device to execute the methods described in each embodiment of this application.

[0261] The above are only preferred embodiments of the present application and do not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A battery pack overcharge diagnosis method, characterized in that: The method comprises: Setting at least one overcharge level, each overcharge level corresponding to a first voltage threshold and a first capacity threshold; Get the maximum voltage of all cells in the battery pack; When the maximum voltage is greater than or equal to the second voltage threshold, the absolute value of the current of the battery pack is less than or equal to the first current threshold, and the duration reaches a first preset time, the battery pack current is integrated in ampere hours; if the absolute value of the capacity increase obtained by the integration is greater than or equal to the first capacity threshold corresponding to a certain overcharge level, the battery pack is determined to be overcharged at the overcharge level; the second voltage threshold is less than the first voltage threshold corresponding to any overcharge level; When the maximum voltage is greater than a first voltage threshold corresponding to any overcharge level, it is determined that the battery pack is overcharged at the overcharge level; When the duration reaches a first preset time, the method further includes: Obtaining a first cell capacity of the cell corresponding to the maximum voltage and a second cell capacity corresponding to the first voltage threshold; A first difference between the second battery cell capacity and the first battery cell capacity is obtained, and the first difference or the product of the first difference and the battery health is used as the first capacity threshold.

2. The battery pack overcharge diagnosis method according to claim 1, wherein: There are multiple overcharge levels, and the first voltage threshold and the first capacity threshold corresponding to the high overcharge level are greater than the first voltage threshold and the first capacity threshold corresponding to the low overcharge level; When determining that the battery pack is overcharged at this overcharge level, the following is also included: The highest level among the overcharge levels of the battery pack is obtained to generate a maximum overcharge level signal so that the battery management system can execute a corresponding protection mechanism according to the maximum overcharge level signal.

3. The battery pack overcharge diagnosis method according to claim 1, wherein: The second voltage threshold is: the product of the charging cut-off voltage and a first preset coefficient.

4. The battery pack overcharge diagnosis method according to claim 1, wherein: Before obtaining the maximum voltage of all cells in the battery pack, the method further includes obtaining the first preset time; the first preset time is obtained based on the second voltage threshold and the first current threshold.

5. The battery pack overcharge diagnosis method according to claim 4, characterized in that: Obtaining the first preset time specifically includes: Setting a second voltage threshold and a first current threshold according to a charging performance parameter curve; The time point at which the voltage is greater than or equal to the second voltage threshold and the absolute value of the current is less than or equal to the first current threshold in the charging performance parameter curve is first defined as the first time point; Calculating the absolute value of the instantaneous rate of change of voltage and the absolute value of the instantaneous rate of change of current at each first interval, and calculating the absolute value of the voltage fluctuation value and the absolute value of the current fluctuation value at each second interval, until simultaneously satisfying: the absolute value of the instantaneous rate of change of voltage and the absolute value of the instantaneous rate of change of current are both less than the first preset rate of change, and the absolute value of the voltage fluctuation value and the absolute value of the current fluctuation value are both less than the first preset fluctuation value, and the time point at this time is regarded as the second time point; and the first interval is less than the second interval; The time difference between the second time point and the first time point is used as the first preset time.

6. The battery pack overcharge diagnosis method according to claim 5, wherein: The second interval time is three times the first interval time.

7. A battery pack over-discharge diagnosis method, characterized in that: The method comprises: Setting at least one over-discharge level, each over-discharge level corresponding to a third voltage threshold and a second capacity threshold; Get the minimum voltage of all cells in the battery pack; When the minimum voltage is less than or equal to a fourth voltage threshold, the absolute value of the current of the battery pack is less than or equal to the second current threshold, and the duration reaches a second preset time, the battery pack current is integrated in ampere hours; if the absolute value of the capacity reduction obtained by the integration is greater than or equal to the second capacity threshold corresponding to a certain over-discharge level, the battery pack is determined to be over-discharged at that over-discharge level; the fourth voltage threshold is greater than the third voltage threshold corresponding to any over-discharge level; When the minimum voltage is less than a third voltage threshold corresponding to any over-discharge level, it is determined that the battery pack is over-discharged at the over-discharge level; When the duration reaches a second preset time, the method further includes: Obtaining a third battery cell capacity of the battery cell corresponding to the minimum voltage and a fourth battery cell capacity corresponding to the third voltage threshold; A second difference between the third battery cell capacity and the fourth battery cell capacity is obtained, and the second difference or the product of the second difference and the battery health is used as the second capacity threshold.

8. The battery pack over-discharge diagnosis method according to claim 7, wherein: There are multiple over-discharge levels, and the third voltage threshold corresponding to the high over-discharge level is smaller than the third voltage threshold corresponding to the low over-discharge level, and the second capacity threshold corresponding to the high over-discharge level is larger than the second capacity threshold corresponding to the low over-discharge level; When the battery pack is judged to be over-discharged at this over-discharge level, the following is also included: The highest over-discharge level among the over-discharge levels of the battery pack is obtained to generate a highest over-discharge level signal so that the battery management system can execute a corresponding protection mechanism according to the highest over-discharge level signal.

9. The battery pack over-discharge diagnosis method according to claim 7, wherein: The fourth voltage threshold is: the product of the discharge cut-off voltage and the second preset coefficient.

10. The battery pack over-discharge diagnosis method according to claim 7, wherein: Before obtaining the minimum voltage of all cells in the battery pack, the method further includes obtaining the second preset time; the second preset time is obtained based on the fourth voltage threshold and the second current threshold.

11. The battery pack over-discharge diagnosis method according to claim 10, wherein: Obtaining the second preset time specifically includes: setting a fourth voltage threshold and a second current threshold according to a discharge performance parameter curve; The time point at which the current reaches a fourth voltage threshold or less and an absolute value of the current reaches a third current threshold for the first time in the discharge performance parameter curve is defined as the third time point; The absolute value of the instantaneous rate of change of voltage and the absolute value of the instantaneous rate of change of current are calculated at each third interval, and the absolute value of the voltage fluctuation value and the absolute value of the current fluctuation value are calculated at each fourth interval, until the following conditions are simultaneously satisfied: the absolute value of the instantaneous rate of change of voltage and the absolute value of the instantaneous rate of change of current are both less than the second preset rate of change, and the absolute value of the voltage fluctuation value and the absolute value of the current fluctuation value are both less than the second preset fluctuation value, and the time point at this time is defined as the fourth time point; the third interval is less than the fourth interval; The time difference between the fourth time point and the third time point is used as the second preset time.

12. The battery pack over-discharge diagnosis method according to claim 11, wherein: The fourth interval time is three times the third interval time.

13. A battery pack diagnostic device for implementing the battery pack overcharge diagnostic method according to claim 1, characterized in that: The device comprises: A setting module, configured to set at least one overcharge level, each overcharge level corresponding to a first voltage threshold and a first capacity threshold; An acquisition module is used to obtain the maximum voltage of all cells in the battery pack; A judgment module is used to integrate the battery pack current in ampere hours when the maximum voltage is greater than or equal to a second voltage threshold, the absolute value of the battery pack current is less than or equal to a first current threshold, and the duration reaches a first preset time; if the absolute value of the capacity increase obtained by the integration is greater than or equal to a first capacity threshold corresponding to a certain overcharge level, the battery pack is determined to be overcharged at that overcharge level; the second voltage threshold is less than the first voltage threshold corresponding to any overcharge level; and when the maximum voltage is greater than the first voltage threshold corresponding to any overcharge level, the battery pack is determined to be overcharged at that overcharge level.

14. A battery pack diagnostic device for implementing the battery pack over-discharge diagnostic method according to claim 7, characterized in that: The device comprises: a setting module for setting at least one over-discharge level, each over-discharge level corresponding to a third voltage threshold and a second capacity threshold; An acquisition module is used to obtain the minimum voltage of all cells in the battery pack; A judgment module is configured to, when the minimum voltage is less than or equal to a fourth voltage threshold, the absolute value of the current of the battery pack is less than or equal to the second current threshold, and the duration reaches a second preset time, perform ampere-hour integration on the battery pack current; if the absolute value of the capacity reduction obtained by the integration is greater than or equal to the second capacity threshold corresponding to a certain over-discharge level, determine that the battery pack is over-discharged at that over-discharge level; the fourth voltage threshold is greater than the third voltage threshold corresponding to any over-discharge level; and when the minimum voltage is less than the third voltage threshold corresponding to any over-discharge level, determine that the battery pack is over-discharged at that over-discharge level.

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