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

Abstract

The invention discloses a battery pack overcharge diagnosis method and device and an overdischarge diagnosis method and device, and relates to the technical field of battery management systems. The method comprises the steps that at least one overcharge grade is set, and each overcharge grade corresponds to a first voltage threshold value and a first capacity threshold value; obtaining the maximum voltage of all battery cells in the battery pack; when the maximum voltage is larger than or equal to a second voltage threshold value, the absolute value of the current of the battery pack is smaller than or equal to a first current threshold value, and the duration time reaches first preset time, ampere-hour integration is carried out on the current of the battery pack; if the absolute value of the capacity increment obtained by integration is greater than or equal to a first capacity threshold value corresponding to a certain overcharge grade, judging that the battery pack is overcharged at the overcharge grade; and when the maximum voltage is greater than a first voltage threshold value corresponding to any overcharge grade, judging that the battery pack is overcharged at the overcharge grade. According to the invention, the voltage and the capacity are combined to diagnose whether overcharge or overdischarge occurs, so that the probability of misjudgment or missed judgment can be effectively reduced, and the accuracy and reliability of diagnosis are improved.

Description

Technical Field

[0001] The present application relates to the technical field of battery management systems, and particularly relates to a method and device for diagnosing overcharge and overdischarge of a battery pack. Background Art

[0002] With the rapid development of applications such as electric vehicles and energy storage devices, battery packs have been widely used. As a key technology for monitoring the state of a battery pack and ensuring the safe, stable and efficient operation of the battery pack, the battery management system (BMS) has also received extensive attention. When the battery pack is at the end of charging and discharging, abnormal conditions such as overcharge and overdischarge are more likely to occur. These two abnormal conditions may cause a decrease in the performance or lifespan of the battery pack, or even cause the battery pack to catch fire and explode, endangering people's lives and property safety. Therefore, if the battery management system can accurately diagnose the abnormal conditions of overcharge and overdischarge of the battery pack in advance, it is of great significance to improve the safety and reliability of the battery system.

[0003] In the related art, the voltage value of each battery cell in the battery pack is compared with a preset voltage threshold. If it exceeds the corresponding threshold, it is determined that the battery pack has an overcharge or overdischarge fault. However, the above 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 method and device for diagnosing overcharge and overdischarge of a battery pack, which can solve the technical problem of easy misjudgment or missed judgment existing in the prior art.

[0005] In a first aspect, the present application provides a method for diagnosing overcharge of a battery pack, the method comprising: 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 battery cells in the battery pack; When the maximum voltage is greater than or equal to a second voltage threshold, the absolute value of the current of the battery pack is less than or equal to a first current threshold, and the duration reaches a first preset time, performing ampere-hour integration on the current of the battery pack; if the absolute value of the increase in the integrated capacity 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 this 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, it is determined that the battery pack is overcharged at this overcharge level.

[0006] In combination with the first aspect, in an implementation manner, a plurality of overcharge levels are provided, and the first voltage threshold and the first capacity threshold corresponding to a higher overcharge level are greater than the first voltage threshold and the first capacity threshold corresponding to a lower overcharge level; When determining overcharge of the battery pack at this overcharge level, it further includes: Obtain the highest level among the overcharge levels of the battery pack overcharge, and generate a highest overcharge level signal therefrom, for the battery management system to execute corresponding protection mechanisms according to the highest overcharge level signal.

[0007] Combined with the first aspect, in one implementation, when the duration reaches the first preset time, it further includes: Obtain the first cell capacity of the cell corresponding to the maximum voltage, and the second cell capacity corresponding to the first voltage threshold; Obtain the first difference between the second cell capacity and the first cell capacity, and use the first difference or the product of the first difference and the battery health as the first capacity threshold.

[0008] Combined with the first aspect, in one implementation, the second voltage threshold is: the product of the charge cut-off voltage and the first preset coefficient.

[0009] Combined with the first aspect, in one implementation, before obtaining the maximum voltage of all cells in the battery pack, it further includes obtaining the first preset time; the first preset time is obtained according to the second voltage threshold and the first current threshold.

[0010] Combined with the first aspect, in one implementation, obtaining the first preset time specifically includes: Set the second voltage threshold and the first current threshold according to the charge performance parameter curve; Take the time point when the voltage first reaches 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 charge performance parameter curve as the first time point; Calculate the absolute value of the instantaneous voltage change rate and the absolute value of the instantaneous current change rate every first interval time, and calculate the absolute value of the voltage fluctuation value and the absolute value of the current fluctuation value every second interval time until both are satisfied: the absolute value of the instantaneous voltage change rate and the absolute value of the instantaneous current change rate are both less than the first preset change rate, 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 take the time point at this time as the second time point; the first interval time is less than the second interval time; Take the time difference between the second time point and the first time point as the first preset time.

[0011] Combined with the first aspect, in one implementation, the second interval time is three times the first interval time.

[0012] In a second aspect, the present application provides a method for diagnosing over-discharge of a battery pack, the method includes: Set at least one over-discharge level, and each over-discharge level corresponds to a third voltage threshold and a second capacity threshold; Obtain the minimum voltage of all the battery cells in the battery pack; 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, perform ampere-hour integration on the battery pack current; if the absolute value of the capacity reduction obtained by integration is greater than or equal to the second capacity threshold corresponding to a certain over-discharge level, it is determined that the battery pack is over-discharged at this over-discharge level; the above-mentioned fourth voltage threshold is greater than the third voltage threshold corresponding to any over-discharge level; When the above-mentioned 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 this over-discharge level.

[0013] Combined with the second aspect, in an implementation manner, there are multiple above-mentioned over-discharge levels, and the third voltage threshold corresponding to a higher over-discharge level is less than the third voltage threshold corresponding to a lower over-discharge level, and the second capacity threshold corresponding to a higher over-discharge level is greater than the second capacity threshold corresponding to a lower over-discharge level; When it is determined that the battery pack is over-discharged at this over-discharge level, it further includes: Obtain the highest level among the over-discharge levels of the battery pack over-discharge, and generate the highest over-discharge level signal therefrom for the battery management system to execute corresponding protection mechanisms according to the above-mentioned highest over-discharge level signal.

[0014] Combined with the second aspect, in an implementation manner, when the duration reaches the second preset time, it further includes: Obtain the third cell capacity of the cell corresponding to the above-mentioned minimum voltage, and the fourth cell capacity corresponding to the above-mentioned third voltage threshold; Obtain the second difference between the above-mentioned third cell capacity and the fourth cell capacity, and use the above-mentioned second difference or the product of the second difference and the battery health as the above-mentioned second capacity threshold; Combined with the second aspect, in an implementation manner, the above-mentioned fourth voltage threshold is: the product of the discharge cut-off voltage and the second preset coefficient; Combined with the second aspect, in an implementation manner, before obtaining the minimum voltage of all the battery cells in the battery pack, it further 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.

[0015] Combined with the second aspect, in an implementation manner, obtaining the second preset time specifically includes: Set the fourth voltage threshold and the second current threshold according to the discharge performance parameter curve; Using the time point when the discharge performance parameter curve first 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 as the third time point; Calculate the absolute value of the instantaneous voltage change rate and the absolute value of the instantaneous current change rate every third interval time, and calculate the absolute value of the voltage fluctuation value and the absolute value of the current fluctuation value every fourth interval time until the following conditions are simultaneously satisfied: both the absolute value of the instantaneous voltage change rate and the absolute value of the instantaneous current change rate are less than the second preset change rate, and both the absolute value of the voltage fluctuation value and the absolute value of the current fluctuation value are less than the second preset fluctuation value, and take the time point at this time as the fourth time point; the above third interval time is less than the fourth interval time; Take the time difference between the fourth time point and the third time point as the above second preset time.

[0016] Combined with the second aspect, in an implementation manner, the above fourth interval time is three times the third interval time.

[0017] In a third aspect, the present application provides a battery pack diagnosis device, and the device includes: A setting module for setting at least one overcharge level, and each overcharge level corresponds to a first voltage threshold and a first capacity threshold; An acquisition module for acquiring the maximum voltage of all battery cells in the battery pack; A judgment module for performing ampere-hour integration on the battery pack current when the above 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; if the absolute value of the capacity increase obtained by 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 this overcharge level; the above second voltage threshold is less than the first voltage threshold corresponding to any overcharge level; and when the above maximum voltage is greater than the first voltage threshold corresponding to any overcharge level, it is determined that the battery pack is overcharged at this overcharge level.

[0018] In a fourth aspect, the present application provides a battery pack diagnosis device, and the device includes: A setting module for setting at least one over-discharge level, and each over-discharge level corresponds to a third voltage threshold and a second capacity threshold; An acquisition module for acquiring the minimum voltage of all battery cells in the battery pack; A judgment module for performing ampere-hour integration on the battery pack current when the above 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; if the absolute value of the capacity decrease obtained by integration is greater than or equal to the second capacity threshold corresponding to a certain over-discharge level, it is determined that the battery pack is over-discharged at this over-discharge level; the above fourth voltage threshold is greater than the third voltage threshold corresponding to any over-discharge level; and 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 this over-discharge level.

[0019] The beneficial effects brought by the technical solution provided in this application include: By setting at least one overcharge level for the battery pack overcharge, each overcharge level corresponding to a first voltage threshold and a first capacity threshold, then obtaining the maximum voltage of all the battery 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 the first preset time, perform ampere-hour integration on the battery pack current; if the absolute value of the capacity increase obtained by 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 this 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, it is determined that the battery pack is overcharged at this overcharge level; By setting at least one over-discharge level for the battery pack over-discharge, each over-discharge level corresponding to a third voltage threshold and a second capacity threshold; obtaining the minimum voltage of all the battery cells in the battery pack, 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 the second preset time, perform ampere-hour integration on the battery pack current; if the absolute value of the capacity decrease obtained by integration is greater than or equal to the second capacity threshold corresponding to a certain over-discharge level, it is determined that the battery pack is over-discharged at this 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, it is determined that the battery pack is over-discharged at this over-discharge level.

[0020] Therefore, by combining voltage and capacity to diagnose overcharge or over-discharge, the probability of misjudgment or missed judgment is effectively reduced, and the accuracy and reliability of the diagnosis are improved, solving the technical problem of easy misjudgment or missed judgment in the related technology. Description of the Drawings

[0021] Figure 1 It is a schematic flowchart of the method for diagnosing overcharge and over-discharge of the battery pack in the embodiment of this application; Figure 2 It is a processing flowchart of the battery management system in the embodiment of this application; Figure 3 It is a schematic diagram of the functional modules of an embodiment of the diagnosis device in this application. Detailed Embodiments

[0022] In order to enable those skilled in the art to better understand the solution of this application, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of this application.

[0023] In a first aspect, an embodiment of the present application provides a method for diagnosing overcharge of a battery pack.

[0024] In one embodiment, the method for diagnosing overcharge of the battery pack of the present application includes: Set at least one overcharge level, and each overcharge level corresponds to a first voltage threshold and a first capacity threshold; Obtain the maximum voltage of all battery cells in the battery pack; When the above maximum voltage is greater than or equal to a second voltage threshold, the absolute value of the current of the battery pack is less than or equal to a first current threshold, and the duration reaches a first preset time, perform ampere-hour integration on the current of the battery pack; wherein, the second voltage threshold is less than the first voltage threshold corresponding to any overcharge level; if the absolute value of the increase in the integrated capacity 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 this overcharge level.

[0025] 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 this overcharge level.

[0026] Wherein, if 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 of simultaneous satisfaction reaches the first preset time, it indicates that the overcharge diagnosis conditions based on voltage for all overcharge levels are satisfied. If the absolute value of the increase in the integrated capacity is greater than or equal to the first capacity threshold corresponding to a certain overcharge level, it indicates that the overcharge diagnosis conditions based on capacity for this overcharge level are satisfied.

[0027] In this embodiment, by setting at least one overcharge level for the overcharge of the battery pack, each overcharge level corresponds to a first voltage threshold and a first capacity threshold, then obtaining the maximum voltage of all battery 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 the first preset time, perform ampere-hour integration on the current of the battery pack; if the absolute value of the increase in the integrated capacity 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 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, it is determined that the battery pack is overcharged at this overcharge level; therefore, by combining voltage and capacity to diagnose overcharge, the probability of misjudgment or missed judgment is effectively reduced, and the accuracy and reliability of the diagnosis are improved, solving the technical problem of easy misjudgment or missed judgment in the related art.

[0028] Based on the above embodiments, in this 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 those 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.

[0029] When determining that the battery pack is overcharged at this overcharge level, it further includes: Obtain the highest level among the overcharge levels of the overcharged battery pack, and generate a highest overcharge level signal therefrom, for the battery management system to execute corresponding protection mechanisms according to the highest overcharge level signal.

[0030] In this embodiment, by setting multiple first voltage thresholds and first capacity thresholds to correspond to multiple overcharge levels, overcharge situations of different severities can be diagnosed, which is convenient for the battery management system to take different countermeasures, so as to protect the battery pack while not completely limiting the performance of the battery and maximizing the battery performance.

[0031] Preferably, according to the severity of overcharge, in the charging situation, there are 3 first voltage thresholds and 3 first capacity thresholds respectively, corresponding to 3 overcharge levels.

[0032] It can be understood that the above overcharge levels can also be divided into other numbers of levels according to actual situations.

[0033] Further, in an embodiment, when the duration reaches the first preset time, it further includes: First, obtain the first cell capacity of the cell corresponding to the maximum voltage, and the second cell capacity corresponding to the first voltage threshold.

[0034] Then, obtain the first difference between the second cell capacity and the first cell capacity, and use the first difference or the product of the first difference and the battery health as the first capacity threshold.

[0035] Optionally, directly use the first difference as the first capacity threshold.

[0036] Preferably, using the product of the first difference and the battery health as the first capacity threshold can consider the capacity attenuation during the use of the cell and further improve the judgment accuracy.

[0037] In this embodiment, when the above 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, it indicates that the battery cell has reached a stable end-of-charge state at this time. Then, the current capacity of the battery cell corresponding to the above maximum voltage can be obtained as the first battery cell capacity, which is used to set the first capacity threshold corresponding to this overcharge level and perform capacity-based diagnosis, and the diagnostic error is relatively small.

[0038] Optionally, the second voltage threshold, the first current threshold, and the first time threshold are set according to the charging performance parameter curve during the battery cell test. The above charging performance parameter curve is the mapping relationship between voltage and current with respect to time during charging.

[0039] Further, in one embodiment, the above second voltage threshold is: the product of the charging cut-off voltage and the first preset coefficient. Optionally, the above first preset coefficient is 0.95 - 0.99.

[0040] Optionally, the above first voltage threshold is slightly greater than the charging cut-off voltage.

[0041] Optionally, before obtaining the maximum voltage of all battery cells in the battery pack, obtaining the first preset time is also included. The above first preset time is obtained according to the above second voltage threshold and the first current threshold.

[0042] Based on the above embodiment, in this embodiment, obtaining the first preset time specifically includes: First, set the second voltage threshold and the first current threshold according to the charging performance parameter curve during the battery cell test.

[0043] Then, in the above charging performance parameter curve, the time point when the voltage first reaches 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 is the first time point A1. Subsequently, calculate the absolute value of the instantaneous voltage change rate and the absolute value of the instantaneous current change rate every first interval time, and calculate the absolute value of the voltage fluctuation value and the absolute value of the current fluctuation value every second interval time until both of the following conditions are met: the calculated absolute value of the instantaneous voltage change rate and the absolute value of the instantaneous current change rate 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 take the time point at this time as the second time point A2, and take the time difference between A2 and A1 as the first preset time.

[0044] Optionally, the first interval time is less than the second interval time.

[0045] Preferably, the second interval time is three times the first interval time.

[0046] In this embodiment, by setting the first preset time, the filtering effect of current and voltage is realized to ensure reaching the end-of-charge state.

[0047] Specifically, when the battery pack is charging, the voltage of the cell with valid voltage reading and the 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, it is determined that the battery pack is overcharged at a certain overcharge level: (1) The maximum voltage is greater than the first voltage threshold corresponding to the overcharge level; (2) The overcharge diagnosis conditions based on voltage and the overcharge diagnosis conditions based on capacity are sequentially satisfied.

[0048] Condition (1) considers the case of overcharge of the cell voltage; condition (2) diagnoses overcharge by integrating capacity and voltage on the basis of considering that the voltage may be overcharged, and this condition considers the case of overcharge of capacity. Therefore, if either condition (1) or condition (2) corresponding to a certain overcharge level is satisfied first, it is determined that the battery pack is overcharged at this level.

[0049] Among them, for condition (2), the overcharge diagnosis conditions based on voltage and the overcharge diagnosis conditions based on capacity need to be sequentially satisfied. The overcharge diagnosis conditions based on voltage are: 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 the first preset time.

[0050] After the overcharge diagnosis conditions based on voltage are satisfied, the overcharge diagnosis based on capacity is carried out. The overcharge diagnosis conditions based on capacity are: starting from the moment when the overcharge diagnosis conditions based on voltage are satisfied, the current of the battery pack 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 the overcharge level, the overcharge diagnosis conditions based on capacity for this overcharge level are also satisfied.

[0051] At this time, when condition (2) is satisfied, it is determined that the battery pack is overcharged at this overcharge level.

[0052] In summary, when an abnormal overcharge situation is diagnosed, the highest level among all overcharge levels is taken, and the generated highest overcharge level signal is sent to the battery management system. When the battery management system receives this highest overcharge level signal, it can execute corresponding overcharge protection measures according to the preset process and protection mechanism.

[0053] In one embodiment, according to the voltage signals collected by each cell sampling line of the battery pack, the cell with valid voltage reading and the maximum voltage value is determined in real time, and this maximum voltage is denoted as V max 。

[0054] It can be understood that the charging cut-off voltage refers to the cell voltage when the battery reaches the fully charged state during the specified constant current charging period. Selecting an appropriate charging cut-off voltage can effectively improve the lifespan of the battery pack. The charging cut-off voltage is an important parameter in the battery charging process, and its setting needs to comprehensively consider the battery's performance, lifespan, and safety. Denote the charging cut-off voltage as V r0 。

[0055] According to the severity of overcharging, the overcharging levels are divided into level 1, level 2, and level 3. The diagnostic conditions and diagnostic thresholds corresponding to each overcharging level are shown in Table 1.

[0056] When the voltage and capacity overcharge diagnosis or voltage overcharge threshold diagnosis of a certain overcharging level is satisfied, it is determined that the overcharging level is established. The satisfaction of the voltage and capacity overcharge diagnosis conditions requires the sequential satisfaction of Condition A and Condition B.

[0057] Table 1 Overcharging Diagnostic Conditions

[0058] Taking overcharging level 1 as an example, the satisfaction of the voltage and capacity overcharge diagnosis conditions requires the sequential satisfaction of Condition A and Condition B. The establishment of Condition A requires the simultaneous satisfaction of (1) and (2), and lasts for t r0 time.

[0059] 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 for (1) in Condition A to be satisfied, which is a calibration value determined by comprehensively considering the cell performance parameters and the test situation of the cell during application.

[0060] is the current flowing through the cell interior, and the absolute value of the current is taken for comparison with the current threshold. Correspondingly, both the first current threshold and the second current threshold are positive values.

[0061] At the end of charging, that is, when approaching the fully charged state, the battery will enter the constant voltage charging stage. At this time, the charging current will gradually decrease until it reaches a relatively low stable current value, indicating that the charging process is about to end. This relatively low stable current value can be regarded as the charging cut-off current. is the current threshold during charging, which is the absolute value of a calibration value determined by comprehensively considering the cell performance parameters and the test situation of the cell during application, and is generally slightly larger than the absolute value of the charging cut-off current. The larger it is, the easier it is for (2) in Condition A to be satisfied. Optionally, is 0.01C to 0.2C (not limited to this range, where 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).

[0062] t r0 is the preset duration that simultaneously meets conditions (1) and (2) in condition A, and is a calibrated value determined by comprehensively considering the cell performance parameters and the test conditions during the cell's application. t r0 The smaller it is, the earlier condition A is met. Optionally, t r0 is 3s to 10s. It can be understood that t r0 is not limited to the above range.

[0063] In summary, 、 and t r0 jointly determine the moment when condition A is met, that is, the moment when the ampere-hour integration of the current starts, so that condition B can be effectively judged.

[0064] Similarly, as shown in Table 1, the condition A for overcharge level 1, level 2, and level 3 is the same during voltage and capacity overcharge diagnosis, that is, the second voltage threshold, the first current threshold, and the preset time are the same when judging condition A.

[0065] Starting from the moment when condition A is met, the absolute value of the capacity increase of the battery pack is calculated in real time using ampere-hour integration, and the calculation formula for its ampere-hour integration is:

[0066] where is the time starting from the moment when condition A of overcharge level 1 is met ( ).

[0067] According to the real-time integration result, the following judgment is made on whether condition B of overcharge level 1 is met:

[0068] where SOH is the state of health of the battery. is the first difference used to determine the first capacity threshold, and the cell performance parameters and the actual application situation of the cell need to be considered. This value is related not only to the performance parameter such as the rated capacity of the cell, but also to the threshold set in condition A, that is, the more stringent the threshold set in condition A (the more difficult it is to meet condition A), the corresponding is smaller. When condition B of overcharge level 1 is also established, the voltage and capacity overcharge diagnosis conditions of overcharge level 1 are met. At this time, it is diagnosed that the battery has an overcharge level 1 fault.

[0069] In this embodiment, considering the fluctuations of voltage and current, a time t r0 redundancy judgment is added to effectively filter the influence of voltage or current fluctuations, that is, to achieve the actual integration of ampere-hours when the stable charging end state is truly reached, so as to reduce the error in the subsequent capacity judgment.

[0070] Among them, when the stable charging end state is truly reached, the capacity level of the current battery cell, that is, the first battery cell capacity, is , and the capacity level of the battery cell corresponding to the first voltage threshold, that is, the second battery cell capacity, is , then taking and as the difference, as . Considering the capacity attenuation during the use of the battery cell, multiply by the SOH as the first capacity threshold.

[0071] Similarly, according to Table 1, the and corresponding to Condition B of overcharge levels 2 and 3 are also obtained in the same way. In this embodiment, . When judging the voltage and capacity overcharge diagnosis conditions of overcharge level 1, according to the corresponding conditions in Table 1, the voltage and capacity overcharge diagnosis conditions of overcharge levels 2 and 3 are also judged simultaneously.

[0072] During the entire charging process, if any of the following conditions is met, it is determined that the overcharge level 1 of the battery pack is established: (1) Conditions A and B in the voltage and capacity overcharge diagnosis corresponding to overcharge level 1 are satisfied in sequence; (2) The voltage overcharge threshold diagnosis condition corresponding to overcharge level 1 is satisfied:

[0073] Among them, is a calibration value determined by comprehensively considering the battery cell performance parameters and the test conditions of the battery cell in application. Similarly, according to Table 1, the determination of overcharge levels 2 and 3 is carried out simultaneously. Among them, the and in the voltage threshold diagnosis conditions of overcharge levels 2 and 3 are also calibration values determined by comprehensively considering the battery cell performance parameters and the test conditions of the battery cell in application. In this embodiment, the first voltage threshold is greater than the charging cut-off voltage, so it satisfies: .

[0074] When overcharge is diagnosed, the highest overcharge level is taken, and the highest overcharge level signal is sent to the battery management system. After receiving this highest-level overcharge signal, the battery management system will respond according to its preset working process and protection mechanism, and execute corresponding overcharge protection measures. For example, charging power limitation or immediate disconnection of the charging circuit, lighting a fault lamp or restricting the activation of the equalization function, etc.

[0075] In a second aspect, the embodiments of the present application further provide a method for diagnosing over-discharge of a battery pack.

[0076] In one embodiment, the method for diagnosing over-discharge of the battery pack of the present application includes: Set at least one over-discharge level, and each over-discharge level corresponds to a third voltage threshold and a second capacity threshold; Obtain the minimum voltage of all battery cells in the battery pack; When the above 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, perform ampere-hour integration on the battery pack current; 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 integration is greater than or equal to the second capacity threshold corresponding to a certain over-discharge level, it is determined that the battery pack is over-discharged at this over-discharge level.

[0077] 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 this over-discharge level. Among them, if 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 of the simultaneous satisfaction reaches the second preset time, it indicates that all over-discharge diagnosis conditions based on voltage for all over-discharge levels are met. If the absolute value of the capacity reduction obtained by integration is greater than or equal to the second capacity threshold corresponding to the first over-discharge level, it indicates that the over-discharge diagnosis condition based on capacity for the first over-discharge level is met.

[0078] In this embodiment, at least one over-discharge level is set for the over-discharge of the battery pack, and each over-discharge level corresponds to a third voltage threshold and a second capacity threshold; the minimum voltage of all the battery 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 current of the battery pack is less than or equal to the second current threshold, and the duration reaches the second preset time, the ampere-hour integration of the battery pack current is performed; if the absolute value of the reduced capacity obtained by integration is greater than or equal to the second capacity threshold corresponding to a certain over-discharge level, it is determined that the battery pack is over-discharged at this 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, it is determined that the battery pack is over-discharged at this over-discharge level. Therefore, by combining voltage and capacity to diagnose over-discharge, the probability of misjudgment or missed judgment is effectively reduced, and the accuracy and reliability of diagnosis are improved, solving the technical problem of easy misjudgment or missed judgment in the related art.

[0079] 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 less 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 greater than the second capacity threshold corresponding to the low over-discharge level.

[0080] When determining that the battery pack is over-discharged at this over-discharge level, it further includes: Obtain the highest level among the over-discharge levels of the battery pack over-discharge, and generate a highest over-discharge level signal therefrom for the battery management system to execute a corresponding protection mechanism according to the above highest over-discharge level signal.

[0081] In this embodiment, by setting multiple third voltage thresholds and second capacity thresholds to correspond to multiple over-discharge levels, over-discharge situations of different severities can be diagnosed, which is convenient for the battery management system to take different countermeasures, so as to protect the battery pack while not completely limiting the performance of the battery and maximizing the battery performance.

[0082] Preferably, according to the severity of over-discharge, in the case of discharging, there are 3 third voltage thresholds and 3 second capacity thresholds respectively, corresponding to 3 over-discharge levels.

[0083] It can be understood that the above over-discharge levels can also be divided into other numbers of levels according to the actual situation.

[0084] Further, in one embodiment, when the duration reaches the second preset time, it further includes: First, obtain the third cell capacity of the cell corresponding to the above minimum voltage, and the fourth cell capacity corresponding to the above third voltage threshold.

[0085] Then, obtain the second difference between the above-mentioned third cell capacity and the fourth cell capacity, and use the second difference or the product of the second difference and the battery health as the above-mentioned second capacity threshold.

[0086] Optionally, directly use the second difference as the second capacity threshold.

[0087] Preferably, use the product of the second difference and the battery health as the second capacity threshold, which can consider the capacity attenuation during the use of the cell and further improve the judgment accuracy.

[0088] 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, it indicates that the cell has reached a stable discharge end state at this time. Then, the current capacity of the cell corresponding to the above-mentioned minimum voltage can be obtained as the third cell capacity, which is used to set the second capacity threshold and perform capacity-based diagnosis with a small diagnostic error.

[0089] Optionally, set the fourth voltage threshold, the second current threshold, and the second time threshold according to the discharge performance parameter curve during the cell test. The above-mentioned discharge performance parameter curve is the mapping relationship of voltage and current with respect to time during discharge.

[0090] Furthermore, in one embodiment, the above-mentioned fourth voltage threshold is: the product of the discharge cut-off voltage and the second preset coefficient. Optionally, the above-mentioned second preset coefficient is 1.01 - 1.03.

[0091] Optionally, in one embodiment, before obtaining the minimum voltage of all cells in the battery pack, it further includes obtaining the second preset time. The above-mentioned second preset time is obtained according to the above-mentioned fourth voltage threshold and the second current threshold.

[0092] Based on the above-mentioned embodiment, in this embodiment, obtaining the second preset time specifically includes: First, set the fourth voltage threshold and the second current threshold according to the discharge performance parameter curve during the cell test.

[0093] Then, in the above discharge performance parameter curve, the time point when the voltage first 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 is the third time point B1. Subsequently, the absolute value of the instantaneous voltage change rate and the absolute value of the instantaneous current change rate are calculated every third interval time, and the absolute value of the voltage fluctuation value and the absolute value of the current fluctuation value are calculated every fourth interval time until both of the following conditions are met simultaneously: the calculated absolute value of the instantaneous voltage change rate and the absolute value of the instantaneous current change rate 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 the fourth time point B2, and the time difference between B2 and B1 is used as the second preset time.

[0094] Optionally, the third interval time is less than the fourth interval time.

[0095] Preferably, the fourth interval time is three times the third interval time.

[0096] In this embodiment, by setting the second preset time, the filtering effect of the current and voltage is realized to ensure reaching the discharge end state.

[0097] Specifically, when the battery pack is discharging, the voltage of the cell with valid voltage and the minimum voltage value 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, it is determined that the battery pack is over-discharged at a certain over-discharge level: (1) The minimum voltage is less than the third voltage threshold corresponding to the over-discharge level; (2) The over-discharge diagnosis conditions based on voltage and the over-discharge diagnosis conditions based on capacity are sequentially satisfied.

[0098] Condition (1) considers the case of over-discharge of voltage; condition (2) combines capacity and voltage to diagnose over-discharge on the basis of considering that the voltage may be over-discharged, and this condition considers the case of over-discharge of capacity. Therefore, if either condition (1) or condition (2) corresponding to a certain over-discharge level is satisfied first, it is determined that the battery pack is over-discharged at this level.

[0099] Among them, condition (2) needs to sequentially satisfy the over-discharge diagnosis conditions based on voltage and the over-discharge diagnosis conditions based on capacity. The over-discharge diagnosis conditions based on voltage are: the minimum voltage is less than or equal to the fourth voltage threshold, and the absolute value of the current of the battery pack is less than or equal to the second current threshold, and the above situation lasts for the second preset time.

[0100] When the over-discharge diagnosis conditions based on voltage are satisfied, the over-discharge diagnosis based on capacity is carried out. The over-discharge diagnosis conditions based on capacity are: starting from the moment when the over-discharge diagnosis conditions based on voltage are satisfied, the current of the battery pack is integrated in ampere-hours. If the reduced value of the integrated capacity is greater than or equal to the second capacity threshold corresponding to the over-discharge level, the over-discharge diagnosis conditions based on capacity for this over-discharge level are also satisfied.

[0101] At this time, condition (2) is satisfied, and it is determined that the battery pack is over-discharged at this over-discharge level.

[0102] In summary, when an abnormal over-discharge situation is diagnosed, the highest level among all over-discharge levels is taken, and the generated highest over-discharge level signal is sent to the battery management system. When the battery management system receives this highest over-discharge level signal, it can execute corresponding over-discharge protection measures according to the preset process and protection mechanism.

[0103] In one embodiment, according to the voltage signals collected by the sampling lines of each cell in the battery pack, the cell with effective voltage and the minimum voltage value is determined in real time, and this minimum voltage is denoted as V min 。

[0104] It can be understood that the discharge cut-off voltage refers to the voltage value at which the cells in the battery pack need to stop discharging when the voltage drops to a certain level during the discharge process. By reasonably setting it, it can be ensured that the cells work within a safe range, avoiding damage to the battery pack caused by over-discharge, thereby extending the service life of the battery pack and contributing to improving the safety of the battery pack. The discharge cut-off voltage is denoted as V d0 。

[0105] According to the severity of over-discharge, the over-discharge levels are divided into level 1, level 2, and level 3. The diagnostic conditions and diagnostic thresholds corresponding to each over-discharge level are shown in Table 2.

[0106] When the voltage and capacity over-discharge diagnosis or voltage over-discharge threshold diagnosis of a certain over-discharge level is satisfied, it is determined that this over-discharge level is established. The satisfaction of the voltage and capacity over-discharge diagnosis conditions requires the sequential satisfaction of condition C and condition D.

[0107] Table 2 Over-discharge diagnostic conditions

[0108] Taking over-discharge level 1 as an example, the satisfaction of the voltage and capacity over-discharge diagnosis conditions requires the sequential satisfaction of condition C and condition D. The establishment of condition C requires the simultaneous satisfaction of (1) and (2), and lasts for t d0 time.

[0109] In condition C, the second preset coefficient is greater than 1. Optionally, The reference value range can be 1.01 - 1.05. The larger it is, the easier it is for (1) of condition C to be satisfied, which is a calibration value determined by comprehensively considering the cell performance parameters and the test situation of the cell in application.

[0110] At the end of discharge, when the voltage drops close to the discharge cut-off voltage, the discharge current also gradually decreases and reaches a lower stable current value. This lower stable current value can be regarded as the discharge cut-off current. is the current threshold during discharge, which is the absolute value of a calibrated value determined comprehensively considering the cell performance parameters and the test conditions during cell application. Generally, it is slightly larger than the absolute value of the discharge cut-off current. The larger, the easier it is to satisfy (2) in condition C. Optionally, is 0.01C to 0.2C (not limited to this range).

[0111] t d0 is the preset duration that simultaneously satisfies (1) and (2) in condition C, which is a calibrated value determined comprehensively considering the cell performance parameters and the test conditions during cell application. t d0 The smaller, the earlier condition C is satisfied. Optionally, t d0 is 3s to 10s.

[0112] In summary, 、 and t d0 jointly determine the moment when condition C is satisfied, that is, the moment when the ampere-hour integration of the current starts, so that condition D can be effectively judged.

[0113] Similarly, as shown in Table 2, the conditions C for over-discharge level 1, level 2, and level 3 during voltage and capacity over-discharge diagnosis are the same, that is, the fourth voltage threshold, the second current threshold, and the preset time during condition C judgment are the same.

[0114] Starting from the moment when condition C is satisfied, the absolute value of the capacity reduction of the battery pack is calculated in real time by ampere-hour integration, and the calculation formula for its ampere-hour integration is:

[0115] Among them, is the time counted from the moment when condition C of over-discharge level 1 is satisfied ( =0).

[0116] According to the real-time integration result, the following judgment is made on whether condition D of over-discharge level 1 is satisfied:

[0117] Among them, SOH is the state of health of the battery. is the second difference used to obtain the second capacity threshold, taking into account the cell performance parameters and the actual application conditions of the cell. This value is related not only to the performance parameter such as the rated capacity of the cell, but also to the threshold set in Condition C, that is, the more stringent the threshold setting in Condition C (the more difficult it is to meet Condition C), the corresponding is larger. When Condition D for over-discharge Level 1 is also satisfied, the voltage and capacity over-discharge diagnostic conditions for over-discharge Level 1 are met. At this time, it is diagnosed that the battery has an over-discharge Level 1 fault.

[0118] In this embodiment, considering the fluctuations of voltage and current, a time t d0 redundant judgment is added to effectively filter the influence of voltage or current fluctuations, that is, to achieve accurate ampere-hour integration only when the stable discharge end state is truly reached, so as to reduce the error in the subsequent capacity judgment.

[0119] Among them, when the stable discharge end state is truly reached, the current cell capacity level, that is, the third cell capacity, is while the cell capacity level corresponding to the third voltage threshold, that is, the fourth cell capacity, is then, using the and difference as . Considering the capacity attenuation during the use of the cell, multiply by SOH as the second capacity threshold.

[0120] Similarly, according to Table 2, the and corresponding to the conditions D for over-discharge Levels 2 and 3 are also obtained in the same way. In this embodiment, . When judging the voltage and capacity over-discharge diagnostic conditions for over-discharge Level 1, according to the corresponding conditions in Table 2, the voltage and capacity over-discharge diagnostic conditions for over-discharge Levels 2 and 3 are also judged.

[0121] During the entire discharge process, if any of the following conditions is met, it is determined that the over-discharge Level 1 of the battery pack is established: (1) The conditions C and D in the voltage and capacity over-discharge diagnosis for over-discharge Level 1 are successively met; (2) The voltage threshold diagnostic condition for over-discharge Level 1 is met:

[0122] Among them, is a calibration value comprehensively determined considering the cell performance parameters and the test conditions of the cell during application. Similarly, as shown in Table 2, over-discharge Levels 2 and 3 are diagnosed simultaneously. Among them, the and It is also a calibration value determined comprehensively considering the cell performance parameters and the test conditions of the cell during application. In this embodiment, the third voltage threshold is less than the discharge cut-off voltage. Therefore, it satisfies: 。

[0123] When over-discharge is diagnosed, the highest over-discharge level is taken, and the highest over-discharge level signal is sent to the battery management system. After receiving this highest over-discharge level signal, the battery management system will respond according to its preset working process and protection mechanism and execute corresponding over-discharge protection measures. For example, discharging power limitation or immediately disconnecting the discharge circuit, lighting a fault lamp or restricting the enabling of the equalization function, etc.

[0124] Optionally, as Figure 1 shown, this embodiment also provides a method for diagnosing overcharge and over-discharge of a battery pack, specifically including: A1. Determine whether the current is a charging condition. If so, go to A2; otherwise, go to A7.

[0125] A2. Obtain the maximum voltage and go to A3 and A4.

[0126] A3. Perform overcharge diagnosis of voltage and capacity and go to A5.

[0127] A4. Perform overcharge threshold diagnosis of voltage; A5. Determine whether the overcharge diagnosis condition of voltage and capacity is satisfied or the overcharge threshold diagnosis condition of voltage is satisfied. If so, go to A6; otherwise, go to A1.

[0128] A6. Determine overcharge.

[0129] A7. Determine whether the current is a discharging condition. If so, go to A8; otherwise, end.

[0130] A8. Obtain the minimum voltage and go to A9 and A10.

[0131] A9. Perform over-discharge diagnosis of voltage and capacity and go to A11.

[0132] A10. Perform over-discharge threshold diagnosis of voltage; A11. Determine whether the over-discharge diagnosis condition of voltage and capacity is satisfied or the over-discharge threshold diagnosis condition of voltage is satisfied. If so, go to A12; otherwise, go to A7.

[0133] A12. Determine over-discharge.

[0134] In this embodiment, the battery pack generally consists of multiple cells. For each cell, a sampling circuit for detecting the cell voltage is arranged inside the battery pack, and the voltage value of each cell can be read in real time; a sampling circuit for detecting the battery pack current is also arranged, and the collected battery pack current value can be read in real time.

[0135] In the charging and discharging conditions respectively, overcharge and over-discharge are each divided into three levels according to the severity of overcharge and over-discharge of the battery pack. Two-condition diagnosis and determination are carried out for each level, and each level has a corresponding threshold.

[0136] Furthermore, as Figure 2 shown, the processing flow of the battery management system for the diagnosis results of overcharge and over-discharge is as follows: B1. Determine whether it is in the charging condition. If so, go to B2; otherwise, go to B3.

[0137] B2. Determine whether the highest overcharge level signal is received. If so, go to B5; otherwise, go to B1.

[0138] B3. Determine whether it is in the discharging condition. If so, go to B4; otherwise, end.

[0139] B4. Determine whether the highest over-discharge level signal is received. If so, go to B5; otherwise, go to B3; B5. Execute the corresponding working process and protection mechanism according to the received level signal.

[0140] In this embodiment, the battery management system can execute corresponding protection measures according to the early-diagnosed overcharge or over-discharge abnormality to ensure the safety of the battery pack. According to the different levels of overcharge or over-discharge occurring, the protection mechanisms of the battery management system include: (1) Limiting the charging and discharging power or immediately disconnecting the charging and discharging circuit; (2) Limiting the enabling of the equalization function; (3) Prohibiting the normal use of the heating or cooling function; (4) Lighting the fault lamp; (5) Notifying the system or the user of the warning information; (6) Recording the relevant data of this overcharge / over-discharge event; (7) Uploading the fault level.

[0141] In some embodiments, since the current at the end of charging and discharging is relatively small, there may be a situation where although the cell voltage does not reach the overcharge or over-discharge voltage threshold, the increase or decrease in its capacity exceeds the corresponding limit value, resulting in a capacity overcharge or over-discharge fault of the battery pack, which will also affect the performance and life of the battery pack.

[0142] In this embodiment, the overcharge and over-discharge of the battery pack are accurately diagnosed by real-time monitoring of the changes in voltage and capacity. On the basis of voltage protection, capacity protection is added, which not only considers the abnormal conditions of overcharge or over-discharge of voltage, but also takes into account the abnormal conditions of overcharge or over-discharge of capacity, and can better characterize the degree of charge and discharge, so as to improve the accuracy of diagnosis. At the same time, by setting different levels of conditions, overcharge and over-discharge of different severities can be diagnosed, which is convenient for the BMS to take different countermeasures. While protecting the battery pack, it will not limit the performance of the battery.

[0143] In a third aspect, an embodiment of the present application further provides a battery pack diagnosis device, as Figure 3 shown. The above device includes a setting module, an acquisition module, and a judgment module.

[0144] The above 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.

[0145] The above acquisition module is used to acquire the maximum voltage of all battery cells in the battery pack.

[0146] The above judgment module is used to perform ampere-hour integration on the battery pack current when the maximum voltage is greater than or equal to a second voltage threshold, the absolute value of the current of the battery pack 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 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 this overcharge level, and 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, it is determined that the battery pack is overcharged at this overcharge level.

[0147] Further, in an 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; When the above judgment module determines that the battery pack is overcharged at this overcharge level, it is further used for: Acquiring the highest level in the overcharge levels of the battery pack overcharge, and generating a highest overcharge level signal therefrom, so that the battery management system can execute a corresponding protection mechanism according to the highest overcharge level signal.

[0148] Further, in an embodiment, the above setting module is further used for: when the duration reaches the first preset time, acquiring the first cell capacity of the cell corresponding to the maximum voltage, and the second cell capacity corresponding to the first voltage threshold; Acquiring a first difference between the second cell capacity and the first cell capacity, and using the first difference or the product of the first difference and the battery health as the first capacity threshold.

[0149] Further, in one embodiment, the second voltage threshold is: the product of the charging cut-off voltage and the first preset coefficient; Further, in one embodiment, before the obtaining module obtains the maximum voltage of all the battery cells in the battery pack, it is further configured to obtain a first preset time; the first preset time is: obtained according to the above-mentioned second voltage threshold and the first current threshold.

[0150] Further, in one embodiment, the obtaining module is further configured to: Set the second voltage threshold and the first current threshold according to the charging performance parameter curve during the cell test; In the above charging performance parameter curve, the time point when the voltage first reaches 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 is the first time point; Calculate the absolute value of the voltage instantaneous change rate and the absolute value of the current instantaneous change rate every first interval time, and calculate the absolute value of the voltage fluctuation value and the absolute value of the current fluctuation value every second interval time until both are satisfied: the absolute value of the voltage instantaneous change rate and the absolute value of the current instantaneous change rate are both less than the first preset change rate, 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 use the time point at this time as the second time point; the first interval time is less than the second interval time; Use the time difference between the second time point and the first time point as the above-mentioned first preset time.

[0151] Further, the second interval time is three times the first interval time.

[0152] Fourthly, an embodiment of the present application further provides a battery pack diagnosis device, and the above device includes a setting module, an obtaining module, and a judging module.

[0153] The above setting module is configured to set at least one over-discharge level, and each over-discharge level corresponds to a third voltage threshold and a second capacity threshold.

[0154] The above obtaining module is configured to obtain the minimum voltage of all the battery cells in the battery pack.

[0155] The above judging module is configured to perform ampere-hour integration on the battery pack current 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 the second preset time; if the absolute value of the reduced capacity obtained by integration is greater than or equal to the second capacity threshold corresponding to a certain over-discharge level, it is determined that the battery pack is over-discharged at this over-discharge level, and 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, it is determined that the battery pack is over-discharged at this over-discharge level.

[0156] Further, in one embodiment, there are multiple over-discharge levels, and the third voltage threshold corresponding to a higher over-discharge level is less than the third voltage threshold corresponding to a lower over-discharge level, and the second capacity threshold corresponding to a higher over-discharge level is greater than the second capacity threshold corresponding to a lower over-discharge level; When the determination module determines that the battery pack is over-discharged at this over-discharge level, it is further configured to: Obtain the highest level in the over-discharge level of the battery pack over-discharge, and generate a highest over-discharge level signal therefrom, for the battery management system to execute a corresponding protection mechanism according to the highest over-discharge level signal.

[0157] Further, in one embodiment, the setting module is further configured to: when the duration reaches a second preset time, obtain the third cell capacity of the cell corresponding to the minimum voltage, and the fourth cell capacity corresponding to the third voltage threshold; Obtain a second difference between the third cell capacity and the fourth cell capacity, and use the second difference or the product of the second difference and the battery health as the second capacity threshold.

[0158] Further, in one embodiment, the fourth voltage threshold is: the product of the discharge cut-off voltage and a second preset coefficient; Further, in one embodiment, before the obtaining module obtains the minimum voltage of all cells in the battery pack, it is further configured to obtain a second preset time; the second preset time is obtained according to the fourth voltage threshold and the second current threshold.

[0159] Further, in one embodiment, the obtaining module is further configured to: Set the fourth voltage threshold and the second current threshold according to the discharge performance parameter curve during cell testing; In the discharge performance parameter curve, the time point when it first 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 is the third time point; Calculate the absolute value of the instantaneous voltage change rate and the absolute value of the instantaneous current change rate every third interval time, and calculate the absolute value of the voltage fluctuation value and the absolute value of the current fluctuation value every fourth interval time until both are satisfied: the absolute value of the instantaneous voltage change rate and the absolute value of the instantaneous current change rate are both less than a second preset change rate, and the absolute value of the voltage fluctuation value and the absolute value of the current fluctuation value are both less than a second preset fluctuation value, and use the time point at this time as the fourth time point; the third interval time is less than the fourth interval time; Use the time difference between the fourth time point and the third time point as the second preset time.

[0160] Further, the fourth interval time is three times the third interval time.

[0161] In other embodiments, the above-mentioned device includes a setting module, an acquisition module, and a judgment module.

[0162] The above-mentioned setting module is used to set at least one overcharge level, each overcharge level corresponding to a first voltage threshold and a first capacity threshold, and to set at least one overdischarge level, each overdischarge level corresponding to a third voltage threshold and a second capacity threshold.

[0163] The above-mentioned acquisition module is used to obtain the maximum voltage of all battery cells in the battery pack under a charging condition; and to obtain the minimum voltage of all battery cells in the battery pack under a discharging condition.

[0164] The above-mentioned judgment module is used to perform ampere-hour integration on the battery pack current when the above-mentioned 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 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 this 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 this overcharge level; it is also used to perform ampere-hour integration on the battery pack current when the above-mentioned minimum voltage is less than or equal to a fourth voltage threshold, the absolute value of the battery pack current is less than or equal to a second current threshold, and the duration reaches a second preset time; if the absolute value of the capacity decrease obtained by integration is greater than or equal to the second capacity threshold corresponding to a certain overdischarge level, it is determined that the battery pack is overdischarged at this overdischarge level, and the above-mentioned fourth voltage threshold is greater than the third voltage threshold corresponding to any overdischarge level; and when the above-mentioned minimum voltage is less than the third voltage threshold corresponding to any overdischarge level, it is determined that the battery pack is overdischarged at this overdischarge level.

[0165] Among them, the function implementation of each module in the above-mentioned device corresponds to each step in the above-mentioned diagnostic method embodiment, and its function and implementation process will not be elaborated here one by one.

[0166] It should be noted that the serial numbers of the above-mentioned embodiments of the present application are only for description and do not represent the superiority or inferiority of the embodiments.

[0167] The terms "including" and "having" and any variations thereof in the specification and claims of the present application and the above-mentioned drawings are intended to cover non-exclusive inclusion. 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 may optionally further include steps or units not listed, or may optionally further include other steps or units inherent to these processes, methods, products, or devices. The descriptions of terms such as "first", "second", and "third" are used to distinguish different objects, etc., and do not represent a sequential order, nor do they limit that "first", "second", and "third" are of different types.

[0168] In some of the processes described in the embodiments of the present application, there are multiple operations or steps that appear in a specific order. However, it should be understood that these operations or steps may not be executed in the order in which they appear in the embodiments of the present application or may be executed in parallel. The serial numbers of the operations are only used to distinguish different operations, and the serial numbers themselves do not represent any order of execution. In addition, these processes may include more or fewer operations, and these operations or steps may be executed in sequence or in parallel, and these operations or steps may be combined.

[0169] Through the description of the above embodiments, those skilled in the art can clearly understand that the above-described embodiment methods can be implemented by means of software plus a necessary general hardware platform. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation. Based on such an understanding, the technical solution of the present application, in essence, or the part that contributes to the prior art 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 several instructions for causing a terminal device to execute the methods described in the various embodiments of the present application.

[0170] The above are only the preferred embodiments of the present application and do not limit the patent scope of the present application. Any equivalent structural or equivalent process transformation made by using the content of the specification and drawings of the present application, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present application.

Claims

1. A method for diagnosing overcharging of a battery pack, characterized in that, The method includes: Setting at least one overcharge level, where each overcharge level corresponds to a first voltage threshold and a first capacity threshold; Obtaining the maximum voltage of all the battery cells in the battery pack; When the maximum voltage is greater than or equal to a second voltage threshold, the absolute value of the current of the battery pack is less than or equal to a first current threshold, and the duration reaches a first preset time, performing ampere-hour integration on the battery pack current; if the absolute value of the increase in the integrated capacity 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 this 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, it is determined that the battery pack is overcharged at this overcharge level.

2. The battery pack overcharge diagnosis method according to claim 1, characterized in that There are multiple overcharge levels, and the first voltage threshold and the first capacity threshold corresponding to a higher overcharge level are greater than the first voltage threshold and the first capacity threshold corresponding to a lower overcharge level; When it is determined that the battery pack is overcharged at this overcharge level, it further includes: Obtaining the highest level among the overcharge levels of the overcharged battery pack, and generating a highest overcharge level signal therefrom for the battery management system to execute a corresponding protection mechanism according to the highest overcharge level signal.

3. The battery pack overcharge diagnosis method according to claim 1, wherein When the duration reaches the first preset time, it further includes: Obtaining the first cell capacity of the cell corresponding to the maximum voltage, and the second cell capacity corresponding to the first voltage threshold; Obtaining the first difference between the second cell capacity and the first cell capacity, and using the first difference or the product of the first difference and the battery health as the first capacity threshold.

4. The battery pack overcharge diagnosis method according to claim 1, characterized in that, The second voltage threshold is: the product of the charge cut-off voltage and a first preset coefficient.

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

6. The battery pack overcharge diagnosis method according to claim 5, characterized in that, Obtaining the first preset time specifically includes: Setting the second voltage threshold and the first current threshold according to the charge performance parameter curve; Taking the time point when the voltage first reaches 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 charge performance parameter curve as the first time point; Calculating the absolute value of the instantaneous voltage change rate and the absolute value of the instantaneous current change rate every first interval time, and calculating the absolute value of the voltage fluctuation value and the absolute value of the current fluctuation value every second interval time until both are satisfied: the absolute value of the instantaneous voltage change rate and the absolute value of the instantaneous current change rate are both less than a first preset change rate, and the absolute value of the voltage fluctuation value and the absolute value of the current fluctuation value are both less than a first preset fluctuation value, and taking the time point at this time as the second time point; the first interval time is less than the second interval time; Taking the time difference between the second time point and the first time point as the first preset time.

7. The battery pack overcharge diagnosis method according to claim 6, characterized in that: The second interval time is three times the first interval time.

8. A method for diagnosing over-discharge of a battery pack, characterized in that, The method includes: Setting at least one over-discharge level, where each over-discharge level corresponds to a third voltage threshold and a second capacity threshold; Obtaining the minimum voltage of all the battery 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 a second current threshold, and the duration reaches a second preset time, perform ampere-hour integration on the current of the battery pack; if the absolute value of the capacity reduction obtained by integration is greater than or equal to a second capacity threshold corresponding to a certain over-discharge level, it is determined that the battery pack is over-discharged at this 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, it is determined that the battery pack is over-discharged at this over-discharge level.

9. The battery pack over-discharge diagnosis method according to claim 8, characterized in that, There are multiple over-discharge levels, and the third voltage threshold corresponding to a higher over-discharge level is less than the third voltage threshold corresponding to a lower over-discharge level, and the second capacity threshold corresponding to a higher over-discharge level is greater than the second capacity threshold corresponding to a lower over-discharge level; When it is determined that the battery pack is over-discharged at this over-discharge level, it further includes: Obtain the highest level among the over-discharge levels of the battery pack over-discharge, and generate a highest over-discharge level signal therefrom, so that the battery management system can execute a corresponding protection mechanism according to the highest over-discharge level signal.

10. The battery pack over-discharge diagnosis method according to claim 8, wherein, When the duration reaches the second preset time, it further includes: Obtain the third cell capacity of the cell corresponding to the minimum voltage, and the fourth cell capacity corresponding to the third voltage threshold; Obtain a second difference between the third cell capacity and the fourth cell capacity, and use the second difference or the product of the second difference and the battery health as the second capacity threshold.

11. The battery pack over-discharge diagnosis method according to claim 8, characterized in that, The fourth voltage threshold is: the product of the discharge cut-off voltage and a second preset coefficient.

12. The battery pack over-discharge diagnosis method according to claim 8, wherein, Before obtaining the minimum voltage of all cells in the battery pack, it further includes obtaining the second preset time; the second preset time is: obtained according to the fourth voltage threshold and the second current threshold.

13. The battery pack over-discharge diagnosis method according to claim 12, wherein Obtaining the second preset time specifically includes: Set the fourth voltage threshold and the second current threshold according to the discharge performance parameter curve; Take the time point when the discharge performance parameter curve first 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 as the third time point; Calculate the absolute value of the instantaneous voltage change rate and the absolute value of the instantaneous current change rate every third interval time, and calculate the absolute value of the voltage fluctuation value and the absolute value of the current fluctuation value every fourth interval time until both are satisfied: the absolute value of the instantaneous voltage change rate and the absolute value of the instantaneous current change rate are both less than a second preset change rate, and the absolute value of the voltage fluctuation value and the absolute value of the current fluctuation value are both less than a second preset fluctuation value, and take the time point at this time as the fourth time point; the third interval time is less than the fourth interval time; Take the time difference between the fourth time point and the third time point as the second preset time.

14. The battery pack over-discharge diagnosis method according to claim 13, wherein: The fourth interval time is three times the third interval time.

15. A battery pack diagnosis device, characterized in that, The device includes: A setting module for setting at least one overcharge level, and each overcharge level corresponds to a first voltage threshold and a first capacity threshold; An acquisition module for acquiring the maximum voltage of all cells in the battery pack; A judgment module, which is used to perform ampere-hour integration on the battery pack current when the maximum voltage is greater than or equal to a second voltage threshold, the absolute value of the current of the battery pack 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 integration is greater than or equal to a first capacity threshold corresponding to a certain overcharge level, it is determined that the battery pack is overcharged at this 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, it is determined that the battery pack is overcharged at this overcharge level.

16. A battery pack diagnostic device, characterized in that, The device includes: A setting module that sets at least one overdischarge level, and each overdischarge level corresponds to a third voltage threshold and a second capacity threshold; An acquisition module, which is used to acquire the minimum voltage of all battery cells in the battery pack; A judgment module, which is used to perform ampere-hour integration on the battery pack current 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 a second current threshold, and the duration reaches a second preset time; if the absolute value of the capacity decrease obtained by integration is greater than or equal to a second capacity threshold corresponding to a certain overdischarge level, it is determined that the battery pack is over-discharged at this overdischarge level; the fourth voltage threshold is greater than the third voltage threshold corresponding to any overdischarge level; and when the minimum voltage is less than the third voltage threshold corresponding to any overdischarge level, it is determined that the battery pack is over-discharged at this overdischarge level.

Images