Battery pack air tightness detection method in ventilation path communication state

Abstract

The invention relates to a battery pack air tightness detection method in a ventilation path communication state, which is applied to a battery pack and comprises a to-be-detected cavity and a functional ventilation structure communicated with the to-be-detected cavity, such as a balance valve, a waterproof ventilation valve or a pressure release valve. According to the method, by obtaining dwell pressure data of similar qualified products, an allowable ventilation reference model is established, and allowable pressure drop characteristics of a functional ventilation structure in a communication state are represented. And after the battery pack is inflated to a preset pressure, entering a pressure maintaining stage, collecting pressure data at a plurality of moments, calculating a pressure drop amount of each adjacent time period, determining an excess pressure drop amount, and calculating an abnormal leakage characterization amount according to the excess pressure drop amount so as to judge the sealing performance of the battery pack. Through combination of two working conditions of positive pressure and negative pressure, the detection accuracy is improved, normal ventilation pressure drop and abnormal leakage pressure drop can be effectively distinguished, misjudgment and missing judgment are avoided, two judgment threshold values are set, refined detection is realized, and it is ensured that sealing detection of the battery pack is more reliable and stable.

Description

Technical Field

[0001] This application relates to the field of airtightness testing technology, and in particular to a method for testing the airtightness of a battery pack under conditions where the air permeability path is connected. Background Technology

[0002] This application relates to the field of battery pack testing technology, and more particularly to a method for testing the airtightness of a battery pack. Battery packs used in applications such as new energy vehicles and energy storage devices typically require excellent sealing performance to meet requirements for dustproofing, waterproofing, environmental adaptability, and long-term operational reliability. Simultaneously, the internal structure of a battery pack is complex, and during operation, it must also balance pressure and provide safe pressure relief. Therefore, functional ventilated structures such as balance valves, waterproof vent valves, and pressure relief valves are commonly incorporated.

[0003] In existing production lines, battery pack airtightness testing typically involves inflating the pack, holding it at pressure, collecting pressure changes, and determining pass / fail based on a pressure drop threshold. During equipment debugging, parameter setting, or test window determination, similar reference samples are usually selected as calibration objects, and the allowable fluctuation range is determined based on their pressure response data under preset test conditions. The sealing status of these reference samples is generally pre-confirmed by existing quality verification, re-inspection, or calibration processes independent of the online testing process. This method is well-suited when the cavity under test can be considered relatively closed. However, in the actual structure of a battery pack, the cavity under test is often connected to the ventilation path of a functional ventilated structure. Under certain production line conditions, due to factors such as structural layout, clamping efficiency, fixture complexity, sealing consistency, or protection requirements for functional components, it is inconvenient to disconnect the connection between the cavity under test and the functional ventilation path during testing.

[0004] At this point, the pressure changes during the pressure holding phase simultaneously include pressure drops caused by normal ventilation due to the functional ventilated structure and pressure drops caused by abnormal leakage. These two components are superimposed, making it difficult to effectively distinguish between pressure changes caused by normal ventilation and those caused by abnormal leakage in the tested cavity using conventional pressure drop threshold methods. This can easily lead to misjudgments or missed judgments, thus affecting the accuracy and consistency of battery pack airtightness testing. Therefore, it is necessary to provide a battery pack airtightness testing method suitable for scenarios where the ventilation path remains connected. Summary of the Invention

[0005] The purpose of this application is to provide a method for detecting the air tightness of a battery pack under conditions where the venting path is connected, so as to solve the problem that it is difficult to effectively distinguish between pressure drop caused by normal ventilation and abnormal leakage in the prior art, and improve the accuracy and consistency of battery pack air tightness detection.

[0006] According to one aspect of this application, a method for testing the airtightness of a battery pack under a connected venting path is provided, applied to a battery pack, the battery pack including a cavity to be tested and a functional venting structure connected to the cavity to be tested, the functional venting structure including at least one of a balance valve, a waterproof venting valve, or a pressure relief valve, and maintaining a connected venting path between the cavity to be tested and the functional venting structure during the testing process; characterized in that the method includes: S10. Obtain pressure data of similar qualified products under preset testing conditions, and establish a permissible ventilation benchmark model. The permissible ventilation benchmark model is at least used to characterize the permissible pressure drop characteristics of the functional breathable structure in the connected state. S20. After inflating the battery pack to the preset detection pressure, it enters the pressure holding stage. S30. During the pressure holding phase, acquire pressure values ​​corresponding to multiple sampling times arranged in chronological order. S40. Based on the pressure values ​​corresponding to the multiple sampling times and the temporal relationship between the sampling times, determine multiple adjacent time periods, and calculate the actual pressure drop of the battery pack in each of the adjacent time periods; S50. Compare the actual pressure drop in each of the adjacent time periods with the allowable pressure drop benchmark for the corresponding time period in the allowable ventilation benchmark model to determine the excess pressure drop corresponding to each of the adjacent time periods; S60. Based on the excess pressure drop corresponding to each of the adjacent time periods, determine the abnormal leakage characterization quantity corresponding to the cavity under test, and determine the sealing performance of the cavity under test according to the abnormal leakage characterization quantity.

[0007] In at least one embodiment of this application, the plurality of sampling times ordered by time sequence include at least a first time, a second time, and a third time, wherein the first time is earlier than the second time, and the second time is earlier than the third time; The plurality of adjacent time periods include at least a first time period and a second time period, wherein the first time period is the time period formed from the first moment to the second moment, and the second time period is the time period formed from the second moment to the third moment.

[0008] In at least one embodiment of this application, the actual pressure drop during the first time period is the greater of zero and the difference between the pressure value at the first moment and the pressure value at the second moment; The actual pressure drop during the second time period is the greater of zero and the difference between the pressure value at the second time and the pressure value at the third time. The permissible ventilation baseline model includes at least the upper limit of permissible pressure drop for the first time period and the upper limit of permissible pressure drop for the second time period; The excess pressure drop corresponding to the first time period is the greater of zero and the difference between the actual pressure drop in the first time period and the upper limit of the allowable pressure drop in the first time period; the excess pressure drop corresponding to the second time period is the greater of zero and the difference between the actual pressure drop in the second time period and the upper limit of the allowable pressure drop in the second time period.

[0009] In at least one embodiment of this application, the abnormal leakage characterization quantity is obtained by weighted calculation of the excess pressure drop corresponding to each of the adjacent time periods; The step of determining the sealing performance of the cavity under test based on the abnormal leakage characterization value specifically includes: when the abnormal leakage characterization value is not greater than the second determination threshold, the sealing performance of the cavity under test is determined to be qualified; When the abnormal leakage characteristic quantity is greater than the second judgment threshold and not greater than the first judgment threshold, the cavity to be tested is determined to be in a re-inspection state. When the abnormal leakage characteristic quantity is greater than the first determination threshold, the test cavity is determined to be unqualified in terms of sealing; wherein, the first determination threshold is greater than the second determination threshold.

[0010] In at least one embodiment of this application, before determining the sealing performance of the cavity under test based on the abnormal leakage characterization, the excess pressure drop corresponding to the second time period is compared with a preset excess pressure drop threshold for the second time period. When the excess pressure drop corresponding to the second time period is greater than the excess pressure drop threshold of the second time period, the test cavity is directly determined to be unqualified in terms of sealing.

[0011] In at least one embodiment of this application, the moment of entering the pressure holding stage is the pressure holding start moment; The first time, the second time, and the third time are the times corresponding to the first preset time, the second preset time, and the third preset time after the pressure holding start time, respectively, and the first preset time is less than the second preset time, and the second preset time is less than the third preset time.

[0012] In at least one embodiment of this application, when establishing the permissible ventilation reference model in S10, the method further includes: under the same preset detection conditions, the same functional ventilation structure installation state, and the same ventilation path connection state as the battery pack under test, obtaining the actual pressure drop of multiple similar qualified products in a first reference period corresponding to the first time period and a second reference period corresponding to the second time period. Wherein, the first reference time period and the first time period have the same duration and time position in the pressure holding stage, and the second reference time period and the second time period have the same duration and time position in the pressure holding stage; Calculate the difference between the actual pressure drop of each qualified product of the same type during the first reference period and the actual pressure drop during the second reference period to obtain a sample set of time period difference values; The reference interval for time-period differences is determined based on the statistical results of the time-period difference sample set. The reference interval for time-period differences includes a lower limit and an upper limit.

[0013] In at least one embodiment of this application, the method further includes: calculating a time period difference characteristic based on the difference between the actual voltage drop of the battery pack under test in the first time period and the actual voltage drop in the second time period; The time period difference feature is compared with the lower limit and upper limit of the time period difference reference interval to determine the time period difference deviation. Wherein, the larger of the following is true: the deviation of the time period difference is zero; the difference between the time period difference feature and the upper limit value; and the difference between the lower limit value and the time period difference feature. The abnormal leakage characteristic quantity is obtained by weighted calculation of the excess pressure drop corresponding to each of the adjacent time periods and the deviation of the time period difference.

[0014] In at least one embodiment of this application, the method further includes performing the following steps under negative pressure detection conditions: After the battery pack is evacuated to a preset negative pressure, it enters the pressure holding stage. During the pressure holding phase, pressure values ​​corresponding to multiple sampling times ordered chronologically are acquired. Based on the pressure values ​​corresponding to multiple sampling times and the temporal relationship between the sampling times, multiple adjacent time periods are determined, and the actual pressure drop of the battery pack in each of the adjacent time periods is calculated. The multiple adjacent time periods include a first working condition time period corresponding to the first time period and a second working condition time period corresponding to the second time period under negative pressure detection conditions. The actual pressure drop in each adjacent time period is compared with the allowable pressure drop benchmark in the allowable ventilation benchmark model to determine the excess pressure drop corresponding to the first operating condition time period and the excess pressure drop corresponding to the second operating condition time period. Based on the difference between the actual voltage drop of the battery pack under test during the first operating period and the actual voltage drop during the second operating period, the time period difference characteristic quantity is calculated, and the time period difference characteristic quantity is compared with the lower limit and upper limit of the time period difference reference interval to determine the time period difference deviation. The abnormal leakage characterization quantity under the negative pressure detection condition is obtained by weighting the excess pressure drop and the deviation of the time difference between adjacent time periods under the negative pressure detection condition.

[0015] In at least one embodiment of this application, the sealing performance of the cavity under test is determined based on both abnormal leakage characteristics under positive pressure and abnormal leakage characteristics under negative pressure testing conditions; wherein, Set a first and a second judgment threshold for positive pressure detection conditions, and a first and a second judgment threshold for negative pressure detection conditions, and the first judgment threshold for each detection condition is greater than the corresponding second judgment threshold. When the abnormal leakage characteristic quantity under positive pressure detection condition and the abnormal leakage characteristic quantity under negative pressure detection condition are both not greater than their respective second judgment thresholds, the sealing performance of the cavity under test is determined to be qualified. When at least one of the abnormal leakage characteristics under positive pressure detection and the abnormal leakage characteristics under negative pressure detection is greater than its corresponding second judgment threshold, and neither is greater than its corresponding first judgment threshold, the cavity under test is determined to be in a re-inspection state. When at least one of the abnormal leakage characteristics under positive pressure testing conditions and the abnormal leakage characteristics under negative pressure testing conditions is greater than its corresponding first judgment threshold, the test cavity is determined to be unqualified in terms of sealing.

[0016] This application has the following beneficial effects: This application, by performing airtightness testing with the venting path open, effectively distinguishes between pressure drop caused by normal ventilation and pressure drop caused by abnormal leakage, solving the problems of misjudgment and missed judgment in existing technologies, thereby greatly improving the accuracy of battery pack sealing performance testing. Considering the special nature of the functional venting structure within the battery pack, this application can perform accurate testing while maintaining the venting path open, solving the problem of not being able to cut off the venting path, allowing it to remain effective even in complex battery pack structures. The combination of positive and negative pressure testing conditions further improves the reliability and stability of the test. By calculating the abnormal leakage characteristics under the two conditions separately and performing weighted calculations, the sealing performance of the battery pack can be more comprehensively evaluated, ensuring adaptability under different operating conditions. This application sets two judgment thresholds (a first judgment threshold and a second judgment threshold), allowing the battery pack to be divided into three states—qualified, re-inspection, and unqualified—under different leakage levels, thereby achieving more refined testing, avoiding blind judgment, and ensuring accurate screening of qualified products. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a flowchart illustrating the steps of a battery pack airtightness testing method under a connected air path, as described in one embodiment of this application. Detailed Implementation

[0019] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0020] Please refer to Figure 1 This embodiment provides a method for testing the airtightness of a battery pack under conditions of open venting paths. This method is applicable to battery pack airtightness testing, particularly in fields such as new energy vehicles and energy storage devices, where battery packs must possess excellent sealing performance to ensure dustproof, waterproof, environmental adaptability, and long-term operational reliability. Battery packs typically contain multiple functional venting structures, such as balance valves, waterproof venting valves, or pressure relief valves. These structures help maintain stable airflow in different operating environments. In this application scenario, this method is used for testing the airtightness of a battery pack under conditions of open venting paths, ensuring that the battery pack's sealing performance is verified through a correct testing process.

[0021] S10. In practical applications, it is necessary to select a battery pack of the same type as the one under test as a reference sample. These reference samples should be tested under the same operating conditions as the battery pack under test. The environmental factors of the test site (such as temperature, humidity, air pressure, etc.) should be consistent with the actual use environment. The inflation device is connected to these reference samples and inflates them to the set test pressure (e.g., 0.5 MPa). After inflation, the pressure holding stage begins. A high-precision pressure sensor is used to monitor and record the pressure value at each moment in real time. The collected data will be used to establish a permissible ventilation baseline model.

[0022] In battery pack testing plants for new energy vehicles or manufacturing sites for energy storage equipment, testing personnel follow this procedure to obtain product data identical to the battery pack design, in order to establish a reference baseline for the battery pack under test. Data from these qualified products ensures the formation of a benchmark model relevant to actual application scenarios.

[0023] S20. In actual operation, the battery pack under test is connected to the inflation device through a pipe, and inflation begins. During inflation, the system continuously injects gas until the battery pack reaches the preset test pressure (e.g., 0.5 MPa). The inflation rate should remain stable during the inflation process to avoid excessively fast or slow gas flow, which could lead to unstable pressure. When the internal pressure of the battery pack reaches the set value, the inflation system automatically stops and enters the pressure holding phase.

[0024] For example, on a new energy vehicle production line, after the battery pack is assembled, testing personnel connect it to an inflation system, set it to an appropriate pressure, monitor pressure changes, and then begin pressure holding. This process ensures that the battery pack can maintain a certain pressure after inflation, simulating its airtightness performance in actual use.

[0025] S30. In this step, the battery pack is kept under pressure, and a pressure sensor is used to collect data at a preset sampling frequency (e.g., once per second). Each time a sample is taken, the sensor records the pressure value at that moment. All collected pressure data are sorted chronologically to form a pressure change data sequence. This data will be used for subsequent pressure drop calculations.

[0026] In battery pack testing equipment, testers set up timed data acquisition devices to record pressure changes within the battery pack in real time during the pressure holding process. This data is then sent to a computing system for further analysis, ensuring that the pressure value at every moment is accurately captured.

[0027] S40. Based on the pressure data collected in step S30, this pressure data needs to be divided into multiple adjacent time periods in chronological order. For example, the first time period is from the first sampling time to the second sampling time, the second time period is from the second sampling time to the third sampling time, and so on. The pressure drop in each time period is calculated as the difference between the pressure values ​​at two adjacent times. For example, the actual pressure drop in the first time period is the pressure value at the first time minus the pressure value at the second time. In this way, the pressure drop in each time period can be obtained, providing basic data for subsequent calculation of excess pressure drop.

[0028] In practice, the testing system automatically determines each time period based on pressure data and calculates the pressure drop within each period. These calculations are displayed in the real-time monitoring system, helping testers confirm whether the battery pack experiences abnormal pressure changes during the pressure holding phase.

[0029] S50. The actual pressure drop in each adjacent time period needs to be compared with the allowable ventilation baseline model established in step S10. If the actual pressure drop exceeds the allowable pressure drop value set in the baseline model, the pressure drop in that time period exceeds the normal ventilation range, and the resulting difference is the excess pressure drop. The specific calculation formula is: Excess pressure drop = Actual pressure drop Permissible pressure drop baseline value.

[0030] During the testing process, the automated system compares the actual voltage drop at each time period with the allowable voltage drop range set in the baseline model. If the voltage drop at any time period exceeds the baseline range, the system will issue a warning, alerting the testing personnel to a potential leakage problem. Testing personnel can use this process to monitor the battery pack's sealing performance in real time and determine if any abnormalities are present.

[0031] S60. The system will perform a weighted calculation of the excess pressure drop in each time period to obtain an overall abnormal leakage characteristic quantity. The purpose of this weighted calculation is to ensure that the time periods with a greater impact on sealing performance receive higher weights based on the importance of the pressure drop in different time periods. After obtaining the abnormal leakage characteristic quantity, it is compared with a preset threshold. If the characteristic quantity is less than the preset second judgment threshold, the battery pack is judged to be qualified in sealing performance; if the characteristic quantity is greater than the second judgment threshold but does not exceed the first judgment threshold, the battery pack is judged to need re-inspection; if it exceeds the first judgment threshold, the battery pack is judged to be unqualified.

[0032] In actual production, testing personnel can determine whether a battery pack is qualified by calculating the abnormal leakage characteristics and combining them with the established acceptance standards. For qualified products, the production process continues; for unqualified products, further re-inspection or return for further inspection are carried out.

[0033] In actual operation, it is necessary to ensure that the battery pack has been inflated to the preset detection pressure according to step S20 and has entered the pressure holding stage. After the pressure holding stage begins, a high-precision pressure sensor is used to collect the internal pressure of the battery pack in real time. The pressure collection time interval is set to once per second (or adjusted according to actual needs) to ensure the accuracy of the sampling data. The pressure sensor will continuously collect pressure values ​​at multiple time points, record the pressure data at these sampling moments, and sort them in chronological order. The multiple sampling moments include at least a first moment, a second moment, and a third moment, and these three moments should meet the following chronological order: the first moment is earlier than the second moment, and the second moment is earlier than the third moment, ensuring that the sampling data has a clear chronological order.

[0034] For example, suppose pressure data is collected at the first, second, and third seconds of the pressure holding phase. These sampling times are the first, second, and third seconds, respectively, forming a time series. Based on the data at these times, the system further divides the data into multiple adjacent time periods. Each time period is determined by two adjacent sampling times. Specifically, the first time period, from the first to the second moment, represents the time interval between the first and second seconds. Secondly, the second time period, from the second to the third moment, represents the time interval between the second and third seconds.

[0035] For each time period, the system will calculate the actual pressure drop within that period. Pressure drop refers to the pressure difference between two adjacent sampling times. The specific calculation method is as follows: The pressure drop in the first period is: Pressure drop in the first period = P1 P2, where P1 is the pressure value at the first moment and P2 is the pressure value at the second moment.

[0036] The pressure drop in the second period is: Pressure drop in the second period = P2 P3, where P2 is the pressure value at the second moment and P3 is the pressure value at the third moment.

[0037] Assuming the pressure at the first moment is 2.5 MPa, the pressure at the second moment is 2.4 MPa, and the pressure at the third moment is 2.3 MPa, then: The pressure drop in the first period is: Pressure drop in the first period = 2.5 MPa 2.4MPa = 0.1MPa The pressure drop during the second period is: Pressure drop during the second period = 2.4 MPa 2.3MPa = 0.1MPa The calculated pressure drop data will serve as a crucial basis for assessing the battery pack's sealing performance. The actual pressure drop at each time period needs to be compared with the allowable pressure drop set in the baseline model to determine if any abnormal leaks or airtightness issues exist. All collected pressure data and calculated pressure drop data will be stored in the data processing system for subsequent analysis.

[0038] During implementation, the actual pressure drop for each adjacent time period will be calculated based on the pressure changes in each period and compared with the allowable pressure drop limit to determine the excess pressure drop. The following are the specific operational and calculation steps for the application scenario to ensure that technicians can accurately reproduce this technical solution.

[0039] After the battery pack is inflated and enters the pressure holding phase, the system calculates the actual pressure drop for each time period based on the pressure value at each sampling moment. Specifically, for the first time period, the actual pressure drop is calculated as the difference between the pressure value at the first moment and the pressure value at the second moment. However, to avoid negative values ​​in the data affecting the results, the calculation method of "the larger of zero and the difference" is adopted. That is, if the calculated pressure drop is negative, the pressure drop for that time period is taken as zero; if the calculated pressure drop is positive, that value is directly used. Therefore, the formula for calculating the actual pressure drop for the first time period is: The actual pressure drop in the first period = max(0, P1) P2) Where P1 represents the pressure value at the first moment, and P2 represents the pressure value at the second moment. Similarly, the actual pressure drop in the second time period is calculated in a similar way, that is, the difference between the pressure value at the second moment and the pressure value at the third moment, taking the larger of zero and the difference. The formula is as follows: The actual pressure drop during the second period = max(0, P2) P3) In the above formula, P2 represents the pressure value at the second moment, and P3 represents the pressure value at the third moment. This calculation method ensures reasonable results even in the absence of a significant pressure drop.

[0040] Furthermore, the system needs to compare the pressure drop with the upper limit set in the permissible ventilation baseline model. The permissible ventilation baseline model typically sets the upper limit for pressure drop for each time period based on experience or previous test data. For example, the upper limit for permissible pressure drop in the first time period might be 0.05 MPa, and in the second time period, it might be 0.04 MPa. The system compares the actual pressure drop for each time period with the corresponding upper limit for permissible pressure drop to calculate the excess pressure drop. The excess pressure drop is the difference between the actual pressure drop and the upper limit for permissible pressure drop. If the actual pressure drop is lower than the upper limit for permissible pressure drop, the excess pressure drop is zero; if the actual pressure drop exceeds the upper limit for permissible pressure drop, the excess pressure drop is the difference between the actual pressure drop and the upper limit for permissible pressure drop. The specific formula is as follows: First period excess pressure drop = max(0, first period actual pressure drop) The first phase allows for the maximum reduction in pressure. Excess pressure drop in the second period = max(0, actual pressure drop in the second period) The second phase allows for a maximum reduction in pressure. In these formulas, the excess pressure drop in the first period is the larger of zero and the difference between the actual pressure drop in the first period and the upper limit of the allowable pressure drop; the excess pressure drop in the second period is calculated similarly.

[0041] Through these calculation steps, the system can accurately identify the excess voltage drop in each time period, providing data support for subsequent calculations of abnormal leakage characteristics. A larger excess voltage drop may indicate a significant abnormal leakage within the battery pack during that time period, thus requiring greater attention.

[0042] These calculations will help testers further determine whether the battery pack's sealing performance is up to standard and provide necessary information for subsequent steps. If the excess voltage drop is significant, further inspection or corrective measures may be required.

[0043] In actual operation, once the battery pack enters the pressure holding phase and begins collecting pressure data, the system calculates the pressure drop for each time period and compares it with the allowable pressure drop benchmark to obtain the excess pressure drop. Furthermore, the excess pressure drop for each time period is combined with a preset weight to calculate the overall abnormal leakage characteristic of the battery pack.

[0044] The excess voltage drop in each time period is assigned different weights according to its importance. Longer time periods may have a greater impact on the battery pack's sealing performance, and therefore can be given higher weights. The weighted calculation formula is as follows: Abnormal leakage characteristic quantity = Σ(w_i × excess pressure drop_i) Where w_i is the weight of the i-th time period, excess voltage drop_i is the excess voltage drop in the i-th time period, and n is the total number of time periods. Weighted calculation can comprehensively evaluate the impact of voltage drop changes in different time periods on the overall sealing performance, ensuring that the calculation results accurately reflect the sealing performance of the battery pack.

[0045] For example, assuming the excess pressure drop in the first period is 0.05 MPa and the excess pressure drop in the second period is 0.02 MPa, and the weight of the first period is 0.7 and the weight of the second period is 0.3, then the abnormal leakage characterization quantity is calculated as follows: The abnormal leakage characteristic value = (0.7 × 0.05) + (0.3 × 0.02) = 0.035 + 0.006 = 0.041 MPa Once the abnormal leakage characteristics are calculated, the next step is to determine the battery pack's sealing performance based on preset threshold values. The determination process is as follows: Pass: When the abnormal leakage indicator is less than or equal to the second judgment threshold, the battery pack is judged to be qualified in terms of sealing.

[0046] Re-inspection: When the abnormal leakage indicator is greater than the second judgment threshold but not greater than the first judgment threshold, the battery pack is determined to be in re-inspection status.

[0047] Unqualified: When the abnormal leakage index is greater than the first judgment threshold, the battery pack is judged to be unqualified in terms of sealing.

[0048] Here, the first judgment threshold should be greater than the second judgment threshold. This segmented judgment allows for a more detailed classification of the airtightness level of the battery pack, enabling appropriate measures such as re-inspection or non-compliance determination to be taken.

[0049] In actual operation, once the battery pack enters the pressure holding stage and pressure data collection begins, the pressure drop for each time period is calculated. The calculation formula is as follows: The pressure drop for the first time period is: Pressure drop in the first period = P1 - P2.

[0050] The pressure drop in the second period is: Pressure drop in the second period = P2 P3.

[0051] Wherein, P1, P2 and P3 represent the pressure values ​​at the first, second and third moments, respectively.

[0052] Furthermore, based on a comparison between the actual pressure drop in each time period and the upper limit of the allowable pressure drop in the baseline model, the excess pressure drop is calculated using the following formula: The excess pressure reduction in the first period is: Excess pressure reduction in the first period = max(0, actual pressure reduction in the first period - allowable pressure reduction limit in the first period).

[0053] The excess pressure drop in the second period is: Excess pressure drop in the second period = max(0, actual pressure drop in the second period - allowable pressure drop limit in the second period).

[0054] If the actual pressure drop is less than the allowable pressure drop, the excess pressure drop is zero; if the actual pressure drop exceeds the allowable pressure drop, the excess pressure drop is the difference between the two. Assuming the actual pressure drop in the first period is 0.1 MPa and the allowable pressure drop limit is 0.05 MPa, and the actual pressure drop in the second period is 0.1 MPa and the allowable pressure drop limit is 0.04 MPa, then: The excess pressure drop in the first period is max(0,0.1-0.05)=0.05MPa.

[0055] The excess pressure drop in the second period is max(0,0.1-0.04)=0.06MPa.

[0056] After calculating the excess voltage drop for each time period, the excess voltage drop for the second time period needs to be processed separately. The excess voltage drop for the second time period is compared with a preset excess voltage drop threshold for that time period. If the excess voltage drop for the second time period exceeds this threshold, the system will directly determine that the battery pack's sealing performance is unqualified, avoiding further unnecessary calculations. In this case, the system will use the following condition: if the excess voltage drop for the second time period exceeds the excess voltage drop threshold for that time period, the battery pack's sealing performance is deemed unqualified. Specifically, assuming the excess voltage drop for the second time period is 0.06 MPa and the excess voltage drop threshold for the second time period is 0.05 MPa, since the excess voltage drop exceeds the threshold, the system immediately determines that the battery pack's sealing performance is unqualified.

[0057] If the excess voltage drop in the second time period does not exceed the set threshold, the system will continue to calculate the abnormal leakage characteristic of the battery pack. The abnormal leakage characteristic is obtained by weighting the excess voltage drop in each time period, and the calculation formula is as follows: Abnormal leakage characteristic quantity = Σ(w_i × excess pressure drop_i) Where w_i is the weight of the i-th time period, excess voltage drop_i is the excess voltage drop of the i-th time period, and n is the total number of time periods. The calculated abnormal leakage characteristic quantity will be used for subsequent sealing performance determination. If the abnormal leakage characteristic quantity is less than or equal to the second determination threshold, the battery pack is deemed to be sealing up to standard; if the abnormal leakage characteristic quantity is greater than the second determination threshold but less than or equal to the first determination threshold, the battery pack is deemed to be in a re-inspection state; if the abnormal leakage characteristic quantity is greater than the first determination threshold, the battery pack is deemed to be sealing up to standard.

[0058] This method allows for the timely identification of battery packs as non-compliant when serious leaks are present. For minor leaks, a weighted calculation of abnormal leakage characteristics further assesses the pack's sealing performance. These steps ensure the accuracy and efficiency of the testing process and enable effective and reasonable judgments based on different leakage levels.

[0059] In this embodiment, when the battery pack enters the pressure holding phase, the system records the pressure holding start time, i.e., the moment when the battery pack reaches the set pressure and begins to maintain a stable pressure. At this time, the device will stop gas injection to keep the pressure inside the battery pack within the set range. The pressure holding start time serves as the starting point for all subsequent sampling times, ensuring that all sampling data are correlated with this moment.

[0060] During the pressure holding phase, the sampling times are recorded sequentially, and the time interval between each sampling time is determined by a preset duration. For example, suppose three sampling times are preset: the first time, the second time, and the third time. The relationship between these times and the pressure holding start time is as follows: First moment: The first preset duration (e.g., 1 second) after the start of pressure holding.

[0061] Second time: The second preset duration (e.g., 2 seconds) after the start of pressure holding.

[0062] Third time: The third preset duration (e.g., 3 seconds) after the start of pressure holding.

[0063] According to this setting, the first time point is the pressure holding start time + 1 second, the second time point is the pressure holding start time + 2 seconds, and the third time point is the pressure holding start time + 3 seconds. In this way, the time interval gradually increases, allowing observation of the pressure changes of the battery pack at different times.

[0064] After collecting pressure data at each moment, the system sorts this data in chronological order. The pressure value at each moment is recorded and transmitted to the data acquisition system to ensure that the collected data accurately reflects the state of the battery pack during the pressure holding phase.

[0065] Furthermore, the collected pressure data is used to calculate the actual pressure drop for each time period. Specifically, the pressure drop for the first time period is the pressure value at the first moment minus the pressure value at the second moment, and the pressure drop for the second time period is the pressure value at the second moment minus the pressure value at the third moment. This pressure drop data will provide a basis for subsequent sealing performance assessment.

[0066] After calculating the voltage drop, it is necessary to compare it with the allowable voltage drop range set in the baseline model to obtain the excess voltage drop. The excess voltage drop for each period is calculated from the difference between the actual voltage drop and the upper limit of the allowable voltage drop. If the actual voltage drop exceeds the allowable voltage drop, an excess voltage drop will occur; otherwise, the excess voltage drop will be zero.

[0067] In this embodiment, to establish a permissible ventilable baseline model, it is specifically necessary to ensure that the installation state of the functional ventilated structure and the connectivity of the ventilated path are consistent with those of the battery pack under test under the same preset testing conditions. This ensures that the baseline model is established under identical conditions, thus providing an accurate comparison standard for subsequent airtightness testing.

[0068] Specifically, select multiple qualified products of the same type as reference objects. These products should have the same design, functional ventilated structure, and ventilated path connectivity as the battery pack under test. Under these conditions, inflate and hold pressure operations are performed on each qualified product of the same type, ensuring that their testing conditions, inflation pressure, and holding time are consistent with those of the battery pack under test.

[0069] Among these qualified products, special attention needs to be paid to their pressure changes during the first and second time periods. Specifically, the actual pressure drop of each qualified product during these two time periods needs to be recorded. These two time periods correspond to the first and second time periods of the battery pack under test, respectively, and their duration and timing should be exactly the same. Specifically: The first reference time period should have the same duration and time position as the first time period of the battery pack under test, starting from the beginning of the pressure holding period and ending at the first time period.

[0070] The second reference time period should have the same duration and time position as the second time period of the battery pack under test, starting from the first moment and ending at the second moment.

[0071] For each qualified product of the same type, the actual pressure drop is calculated for the first reference time period and the second reference time period, respectively. The pressure drop is obtained by calculating the pressure change within each time period. For example, assuming the pressure data for the first reference time period are P4 and P5, and the pressure data for the second reference time period are P5 and P6, then: The actual pressure drop during the first reference period was: P4 P5.

[0072] The actual pressure drop during the second reference period was: P5 P6.

[0073] After calculating the actual pressure drop of each qualified product of the same type in these two time periods, the next step is to calculate the time period difference. The time period difference refers to the difference in pressure drop between the first reference time period and the second reference time period for qualified products of the same type. The specific calculation formula is as follows: Time difference = | Actual pressure drop during the first reference time period Actual pressure drop during the second reference period | By performing this calculation on all similar qualified products, a time-period difference sample set is obtained, which reflects the pressure drop difference between the first and second time periods for different qualified products under the same testing conditions.

[0074] Furthermore, statistical analysis is performed using a sample set of time-period difference values ​​to determine a reference interval for the time-period difference values. This reference interval includes a lower limit and an upper limit, which represent the maximum and minimum pressure drop changes during normal airtightness testing, respectively. These upper and lower limits are calculated based on the maximum and minimum values ​​in the sample set of time-period difference values ​​and serve as a benchmark for judging whether the battery pack is qualified. The statistical analysis steps include calculating the mean, standard deviation, and maximum and minimum differences of the sample set to ensure that the reference interval is representative and can accommodate minor differences between different products.

[0075] This step yields a reference range for time-period differences, which serves as a criterion for subsequent battery pack testing. In subsequent tests, the voltage drop of the battery pack under test at each time period will be compared with this reference range, thus providing an accurate basis for judging the battery pack's sealing performance.

[0076] Under negative pressure testing conditions, the battery pack is evacuated to reach a preset negative pressure. This step simulates the battery pack's operation under lower pressure, ensuring it maintains airtightness under varying pressure environments. The evacuation device reduces the pressure inside the battery pack to a preset value (e.g., -0.5 MPa), and then the pack enters a pressure-holding phase, maintaining a stable negative pressure within the battery pack.

[0077] Under negative pressure testing conditions, a high-precision pressure sensor is used to collect the pressure data of the battery pack in real time. Each sample records the pressure value at the current moment, ensuring that the sampling times are arranged in chronological order, typically using a sampling frequency of once per second. The collected data will then include multiple sampling times, which will be sorted according to time sequence and contain data consistent with the actual pressure drop changes of the battery pack under test.

[0078] Based on the temporal relationship between the collected pressure data and the sampling times, these times can be divided into multiple adjacent time periods. For example, the first operating condition time period and the second operating condition time period can be defined as the first time period and the second time period, respectively. The division of these time periods should correspond to the actual working conditions of the battery pack under test under negative pressure.

[0079] Specifically: First operating condition period: This corresponds to the first period of the battery pack under negative pressure detection conditions. The voltage drop during this period is the change from the first moment to the second moment.

[0080] Second operating condition period: This corresponds to the second period of the battery pack under negative pressure detection conditions. The voltage drop during this period is the change from the second moment to the third moment.

[0081] Next, by calculating the actual pressure drop in each time period, the pressure drop data for adjacent time periods can be obtained. For example: The actual pressure drop during the first operating period is P1-P2, where P1 and P2 are the pressure values ​​at the first and second moments, respectively.

[0082] The actual pressure drop during the second operating period is P2-P3, where P2 and P3 are the pressure values ​​at the second and third moments, respectively.

[0083] After calculating the actual pressure drop for each time period, the next step is to compare the actual pressure drop for each time period with the allowable pressure drop baseline for the corresponding time period in the allowable ventilation baseline model. Specifically: The excess pressure drop during the first operating period is: Excess pressure drop during the first operating period = max(0, actual pressure drop during the first operating period - allowable pressure drop baseline during the first operating period) The excess pressure drop during the second operating condition period is: Excess pressure drop during the second operating period = max(0, actual pressure drop during the second operating period - allowable pressure drop benchmark during the second operating period) If the actual pressure drop is less than the allowable pressure drop range, the excess pressure drop is zero; if the actual pressure drop exceeds the allowable pressure drop range, the excess pressure drop is equal to the difference between the two.

[0084] Next, the time-period difference characteristic is calculated. The time-period difference characteristic refers to the difference in voltage drop between adjacent time periods (i.e., the first operating condition period and the second operating condition period), reflecting the pressure changes of the battery pack under different operating conditions. The calculation formula is: Time-period difference characteristic quantity = |Actual pressure drop during the first operating condition period - Actual pressure drop during the second operating condition period| For example, assuming the actual pressure drop during the first operating condition period is 0.1 MPa and the actual pressure drop during the second operating condition period is 0.08 MPa, then the characteristic quantity of the time period difference is: The time-period difference characteristic value = |0.1-0.08| = 0.02 MPa Then, the time-period difference characteristic is compared with a preset time-period difference reference interval. The upper and lower limits of the time-period difference reference interval are derived statistically from a set of difference samples of similar qualified products. This reference interval represents the range of pressure drop changes that may occur during normal airtightness testing.

[0085] The formula for calculating the deviation of the time difference is: Time period difference deviation = max(0, |Time period difference feature value - Upper limit|, |Time period difference feature value - Lower limit|) If the time difference characteristic falls within the reference interval, the deviation is zero; if it exceeds the reference interval, the deviation is equal to the larger of the upper or lower limit of the deviation interval.

[0086] Finally, based on the excess pressure drop and time-period deviation at each time point under negative pressure testing conditions, the abnormal leakage characterization quantity under negative pressure testing conditions is obtained through weighted calculation. The calculation formula is: Abnormal leakage characteristic quantity = Σ(w_k × (excess pressure drop_k + time period difference deviation_k)) Where w_k is the weight of the k-th time period, excess pressure drop_k is the excess pressure drop of the k-th time period, time period difference deviation_k is the time period difference deviation of the k-th time period, and m is the total number of time periods.

[0087] In this embodiment, pressure data of the battery pack under test needs to be collected under both positive and negative pressure testing conditions, and abnormal leakage characteristics need to be calculated. By setting the judgment thresholds corresponding to the positive and negative pressure testing conditions respectively, the calculated abnormal leakage characteristics will be used for subsequent sealing performance judgment. The abnormal leakage characteristics of the positive and negative pressure testing conditions are obtained by weighted calculation of the excess pressure drop and the deviation of the time period for each time period.

[0088] Specifically, a first and a second judgment threshold are set for positive and negative pressure testing conditions. The first judgment threshold for positive pressure testing is greater than the second judgment threshold, and the first judgment threshold for negative pressure testing is also greater than the second judgment threshold. These thresholds are used to determine the battery pack's sealing performance. For abnormal leakage characteristics under positive and negative pressure conditions, the following judgments are made: When the abnormal leakage characteristics under both positive and negative pressure testing conditions are not greater than their respective second judgment thresholds, the battery pack is deemed to be in good condition. This means that the leakage level of the battery pack is within acceptable limits under both testing conditions.

[0089] When at least one of the abnormal leakage characteristics under positive pressure testing and negative pressure testing is greater than the corresponding second judgment threshold, and neither is greater than their respective first judgment threshold, the battery pack is judged to be in re-inspection status, indicating that the leakage degree of the battery pack exceeds the normal tolerance range, but does not reach the level of serious leakage, and further testing and confirmation are required.

[0090] When at least one of the abnormal leakage characteristics under positive pressure testing conditions and the abnormal leakage characteristics under negative pressure testing conditions exceeds its corresponding first judgment threshold, the battery pack is judged to be unqualified in terms of sealing, which means that the leakage degree of the battery pack has exceeded the specified maximum tolerance and cannot meet the airtightness requirements.

[0091] This method determines the battery pack's sealing performance based on abnormal leakage characteristics under two different testing conditions: positive and negative pressure. This allows for a comprehensive assessment of the battery pack's sealing performance under varying environmental conditions, ensuring accurate detection and reasonable assessment of leaks under different pressures. By setting different thresholds and combining them with the relationship between leakage characteristics under different testing conditions, this method provides a more precise testing solution, avoiding simplistic, single-standard approaches.

[0092] The embodiments described above are merely examples of several implementations of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the scope of protection of this application.

Claims

1. A method for detecting the airtightness of a battery pack under conditions of continuous airflow path, applied to a battery pack, the battery pack comprising a cavity to be tested and a functional air-permeable structure communicating with the cavity to be tested, the functional air-permeable structure comprising at least one of a balance valve, a waterproof air-permeable valve, or a pressure relief valve, and maintaining the airflow path communication between the cavity to be tested and the functional air-permeable structure during the testing process; characterized in that, The method includes: S10. Obtain pressure data of similar qualified products under preset testing conditions, and establish a permissible ventilation benchmark model. The permissible ventilation benchmark model is at least used to characterize the permissible pressure drop characteristics of the functional breathable structure in the connected state. S20. After inflating the battery pack to the preset detection pressure, it enters the pressure holding stage. S30. During the pressure holding phase, acquire pressure values ​​corresponding to multiple sampling times arranged in chronological order. S40. Based on the pressure values ​​corresponding to the multiple sampling times and the temporal relationship between the sampling times, determine multiple adjacent time periods, and calculate the actual pressure drop of the battery pack in each of the adjacent time periods; S50. Compare the actual pressure drop in each of the adjacent time periods with the allowable pressure drop benchmark for the corresponding time period in the allowable ventilation benchmark model to determine the excess pressure drop corresponding to each of the adjacent time periods; S60. Based on the excess pressure drop corresponding to each of the adjacent time periods, determine the abnormal leakage characterization quantity corresponding to the cavity under test, and determine the sealing performance of the cavity under test according to the abnormal leakage characterization quantity.

2. The method for detecting the airtightness of a battery pack under conditions of open permeable paths according to claim 1, characterized in that, The plurality of sampling times ordered by time sequence include at least a first time, a second time, and a third time, wherein the first time is earlier than the second time, and the second time is earlier than the third time; The plurality of adjacent time periods include at least a first time period and a second time period, wherein the first time period is the time period formed from the first time to the second time, and the second time period is the time period formed from the second time to the third time.

3. The method for detecting the airtightness of a battery pack under conditions of continuous air permeability paths according to claim 2, characterized in that, The actual pressure drop during the first time period is the greater of zero and the difference between the pressure value at the first moment and the pressure value at the second moment. The actual pressure drop during the second time period is the greater of zero and the difference between the pressure value at the second time and the pressure value at the third time. The permissible ventilation baseline model includes at least the upper limit of permissible pressure drop for the first time period and the upper limit of permissible pressure drop for the second time period; The excess pressure drop corresponding to the first time period is the greater of the difference between zero and the actual pressure drop in the first time period minus the upper limit of the allowable pressure drop in the first time period; the excess pressure drop corresponding to the second time period is the greater of the difference between zero and the actual pressure drop in the second time period minus the upper limit of the allowable pressure drop in the second time period.

4. The method for detecting the airtightness of a battery pack under conditions of continuous air permeability paths according to claim 3, characterized in that, The abnormal leakage characteristic quantity is obtained by weighted calculation of the excess pressure drop corresponding to each of the adjacent time periods; The step of determining the sealing performance of the cavity under test based on the abnormal leakage characterization value specifically includes: when the abnormal leakage characterization value is not greater than the second determination threshold, the sealing performance of the cavity under test is determined to be qualified; When the abnormal leakage characteristic quantity is greater than the second judgment threshold and not greater than the first judgment threshold, the cavity to be tested is determined to be in a re-inspection state. When the abnormal leakage characteristic quantity is greater than the first determination threshold, the test cavity is determined to be unqualified in terms of sealing; wherein, the first determination threshold is greater than the second determination threshold.

5. The method for detecting the airtightness of a battery pack under conditions of continuous air permeability paths according to claim 4, characterized in that, Before determining the sealing performance of the cavity under test based on the abnormal leakage characterization, the excess pressure drop corresponding to the second time period is compared with the preset excess pressure drop threshold for the second time period. When the excess pressure drop corresponding to the second time period is greater than the excess pressure drop threshold of the second time period, the test cavity is directly determined to be unqualified in terms of sealing.

6. The method for detecting the airtightness of a battery pack in a connected air-permeable path state according to claim 2, characterized in that, The moment when the pressure holding phase begins is the pressure holding start moment; The first time, the second time, and the third time are the times corresponding to the first preset time, the second preset time, and the third preset time after the pressure holding start time, respectively, and the first preset time is less than the second preset time, and the second preset time is less than the third preset time.

7. The method for detecting the airtightness of a battery pack under conditions of continuous air permeability paths according to claim 3, characterized in that, When establishing the permissible ventilation reference model in S10, it also includes: under the same preset detection conditions, the same functional ventilation structure installation state, and the same ventilation path connection state as the battery pack under test, obtaining the actual pressure drop of multiple similar qualified products in the first reference period corresponding to the first time period and the second reference period corresponding to the second time period; Wherein, the first reference time period and the first time period have the same duration and time position in the pressure holding stage, and the second reference time period and the second time period have the same duration and time position in the pressure holding stage; Calculate the difference between the actual pressure drop of each qualified product of the same type during the first reference period and the actual pressure drop during the second reference period to obtain a sample set of time period difference values; The reference interval for time-period differences is determined based on the statistical results of the time-period difference sample set. The reference interval for time-period differences includes a lower limit and an upper limit.

8. The method for detecting the airtightness of a battery pack under conditions of continuous air permeability paths according to claim 7, characterized in that, The method further includes: calculating a time period difference characteristic quantity based on the difference between the actual voltage drop of the battery pack under test in the first time period and the actual voltage drop in the second time period; The time period difference feature is compared with the lower limit and upper limit of the time period difference reference interval to determine the time period difference deviation. Wherein, the larger of the following is true: the deviation of the time period difference is zero; the difference between the time period difference feature and the upper limit value; and the difference between the lower limit value and the time period difference feature. The abnormal leakage characteristic quantity is obtained by weighted calculation of the excess pressure drop corresponding to each of the adjacent time periods and the deviation of the time period difference.

9. The method for detecting the airtightness of a battery pack in a connected air-permeable path state according to claim 8, characterized in that, The method further includes performing the following steps under negative pressure detection conditions: After the battery pack is evacuated to a preset negative pressure, it enters the pressure holding stage. During the pressure holding phase, pressure values ​​corresponding to multiple sampling times ordered chronologically are acquired. Based on the pressure values ​​corresponding to multiple sampling times and the temporal relationship between the sampling times, multiple adjacent time periods are determined, and the actual pressure drop of the battery pack in each of the adjacent time periods is calculated. The multiple adjacent time periods include a first working condition time period corresponding to the first time period and a second working condition time period corresponding to the second time period under negative pressure detection conditions. The actual pressure drop in each adjacent time period is compared with the allowable pressure drop benchmark in the allowable ventilation benchmark model to determine the excess pressure drop corresponding to the first operating condition time period and the excess pressure drop corresponding to the second operating condition time period. Based on the difference between the actual voltage drop of the battery pack under test during the first operating period and the actual voltage drop during the second operating period, the time period difference characteristic quantity is calculated, and the time period difference characteristic quantity is compared with the lower limit and upper limit of the time period difference reference interval to determine the time period difference deviation. The abnormal leakage characterization quantity under the negative pressure detection condition is obtained by weighting the excess pressure drop and the deviation of the time difference between adjacent time periods under the negative pressure detection condition.

10. The method for detecting the airtightness of a battery pack under conditions of continuous air permeability paths according to claim 9, characterized in that, The sealing performance of the cavity under test is determined jointly based on abnormal leakage characteristics under positive pressure and negative pressure testing conditions; wherein... Set a first and a second judgment threshold for positive pressure detection conditions, and a first and a second judgment threshold for negative pressure detection conditions, and the first judgment threshold for each detection condition is greater than the corresponding second judgment threshold. When the abnormal leakage characteristic quantity under positive pressure detection condition and the abnormal leakage characteristic quantity under negative pressure detection condition are both not greater than their respective second judgment thresholds, the sealing performance of the cavity under test is determined to be qualified. When at least one of the abnormal leakage characteristics under positive pressure detection conditions and the abnormal leakage characteristics under negative pressure detection conditions is greater than its corresponding second judgment threshold, and neither is greater than its corresponding first judgment threshold, the cavity under test is determined to be in a re-inspection state. When at least one of the abnormal leakage characteristics under positive pressure testing conditions and the abnormal leakage characteristics under negative pressure testing conditions is greater than its corresponding first judgment threshold, the test cavity is determined to be unqualified in terms of sealing.

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