Battery immersion liquid insulation detection device and detection method

Abstract

The application provides a battery immersion liquid insulation detection device and method. The device comprises: a resistivity acquisition module arranged in the immersion liquid of a battery module, used for acquiring the resistivity of the immersion liquid; a dielectric constant acquisition module arranged in the immersion liquid, used for acquiring the dielectric constant of the immersion liquid; an insulation impedance acquisition module electrically connected with a battery cluster, used for acquiring the insulation impedance of the positive and negative electrodes of the battery cluster to the ground; and a control module electrically connected with the resistivity acquisition module, the dielectric constant acquisition module and the insulation impedance acquisition module, respectively, used for controlling the output of the immersion liquid insulation detection result according to the resistivity, the dielectric constant and the insulation impedance. The application acquires the electrical parameters of the immersion liquid and the insulation impedance of the battery cluster through the resistivity acquisition module, the dielectric constant acquisition module and the insulation impedance acquisition module, respectively, integrates and analyzes through the control module, realizes comprehensive acquisition and accurate detection, and greatly improves the accuracy of the battery immersion liquid insulation detection.

Description

Technical Field

[0001] This application relates to, but is not limited to, the field of insulation testing technology, and in particular to a battery immersion fluid insulation testing device and a battery immersion fluid insulation testing method. Background Technology

[0002] Lithium-ion batteries used in data center energy storage systems have gradually become the mainstream in the market due to their advantages such as high energy density, small footprint, and long cycle life. However, their safety hazards are prominent, and several serious fire accidents caused by thermal runaway have occurred in recent years. With the continuous improvement of battery charge and discharge rates and energy density, the technology of fully immersing batteries in insulating cooling oil has become a key technological direction and mainstream application solution for improving lithium-ion battery safety. Immersion fluid can achieve rapid and uniform heat dissipation and effectively suppress the spread of fire; immersion energy storage typically injects immersion fluids such as hydrocarbon synthetic oil, silicone oil, and fluorinated liquid into battery modules with an IP67 sealing rating. However, during long-term operation, the oil is prone to problems such as water ingress, aging, or leakage of electrolyte from the battery cells, leading to a decline in insulation performance and a significant reduction in safety protection effectiveness.

[0003] Currently, most data centers and energy storage sites are edge nodes, characterized by unattended operation, remote geographical locations, and inconvenient maintenance. Furthermore, battery immersion fluids are hazardous industrial liquids, and to prevent evaporation and leakage, battery modules often employ IP67 sealing structures, making on-site disassembly and maintenance extremely difficult. Therefore, automated, unmanned, and low-cost online real-time monitoring technology has become a necessity. However, existing online monitoring solutions generally have lower accuracy than dedicated testing instruments. Improving the accuracy of online real-time monitoring has become a pressing technical problem for the industry. Summary of the Invention

[0004] This application aims to solve one of the technical problems in the related art to a certain extent, and provides a battery immersion liquid insulation testing device and a battery immersion liquid insulation testing method.

[0005] A first aspect of this application provides a battery immersion fluid insulation detection device, comprising: A resistivity acquisition module is installed in the immersion liquid of the battery module to acquire the resistivity of the immersion liquid; A dielectric constant acquisition module is installed in the immersion liquid and is used to acquire the dielectric constant of the immersion liquid; An insulation impedance acquisition module is electrically connected to the battery cluster and is used to acquire the insulation impedance of the positive and negative terminals of the battery cluster to ground. The battery cluster includes multiple battery modules connected in series. The control module is electrically connected to the resistivity acquisition module, the dielectric constant acquisition module, and the insulation impedance acquisition module, respectively, and is used to control the output of the immersion liquid insulation detection result based on the resistivity, the dielectric constant, and the insulation impedance.

[0006] A second aspect of this application provides a method for detecting the insulation of a battery immersion fluid, the method comprising: The dielectric constant and resistivity of the immersion liquid in the battery module are collected, and the insulation impedance of the positive and negative electrodes of the battery cluster to ground is collected. The battery cluster includes multiple battery modules connected in series. Based on the resistivity, dielectric constant, and insulation impedance, the immersion liquid insulation test results are output.

[0007] The technical solution provided in this application can achieve the following beneficial effects: By immersing the resistivity and dielectric constant acquisition modules in the submerged liquid, the resistivity and dielectric constant parameters of the submerged liquid are collected. Furthermore, the insulation impedance acquisition module collects the insulation impedance of the positive and negative electrodes of the battery cluster to ground. The control module then performs comprehensive analysis of these parameters. The resistivity, dielectric constant, and insulation impedance acquisition modules of this application are integrated into the battery energy storage system, eliminating the need for additional independent testing equipment. This enables online monitoring of the battery energy storage system, resulting in convenient overall deployment and low overall application cost. Simultaneously, this application achieves comprehensive acquisition of the electrical characteristics of the submerged liquid and the insulation state of the battery cluster, and accurately outputs insulation detection results through multi-parameter fusion judgment, significantly improving the comprehensiveness, accuracy, and reliability of battery submerged liquid insulation detection, providing strong protection for the safe and stable operation of the submerged energy storage system. Attached Figure Description

[0008] Figure 1 This is a structural diagram of a data center energy storage system provided by related technologies; Figure 2 This application provides a structure for a battery immersion fluid insulation testing device. Figure 1 ; Figure 3 This application provides a structure for a battery immersion fluid insulation testing device. Figure 2 ; Figure 4 This is a schematic diagram of the battery cluster structure provided in the embodiments of this application; Figure 5 A schematic flowchart illustrating a battery immersion fluid insulation testing method provided in this application embodiment; Figure 6 This is a schematic diagram of the overall process of a battery immersion fluid insulation testing method provided in an embodiment of this application; Figure 7A schematic diagram of a dielectric constant acquisition process provided for an embodiment of this application; Figure 8 A schematic flowchart of an insulation impedance acquisition method provided in this application embodiment. Figure 1 ; Figure 9 A schematic flowchart of an insulation impedance acquisition method provided in this application embodiment. Figure 2 ; Figure 10 This is a schematic diagram of a resistivity acquisition process provided in an embodiment of this application. Detailed Implementation

[0009] To make the objectives, technical methods, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0010] It should be noted that although the flowchart shows a logical order, in some cases, the steps shown or described may be performed in a different order than that shown in the flowchart. In the description of the specification, claims, and the foregoing drawings, "at least one" means one or more; "more than" means two or more; "greater than," "less than," and "exceeding" are understood to exclude the stated number; "above," "below," and "within" are understood to include the stated number. The use of terms such as "first," "second," etc., is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly specifying the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0011] In this embodiment, "and / or" describes the relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the existence of A alone, the simultaneous existence of A and B, or the existence of B alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following associated objects are in an "or" relationship. "At least one of the following" and similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, at least one of a, b, and c can represent: the existence of a alone, the existence of b alone, the existence of c alone, the simultaneous existence of a and b, the simultaneous existence of a and c, the simultaneous existence of b and c, or the simultaneous existence of a, b, and c, where a, b, and c can be single or multiple.

[0012] In the embodiments of this application, the words "exemplarily" or "for example" are used to indicate examples, illustrations, or explanations. Any embodiment or design described as "exemplarily" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design solutions. Specifically, the use of the words "exemplarily" or "for example" is intended to present the relevant concepts in a specific manner.

[0013] To facilitate a better understanding and explanation of the solutions in the embodiments of this application, some concepts involved in the embodiments of this application will be explained below.

[0014] Data center energy storage systems initially used lead-acid batteries, but now lithium batteries are more commonly used. Lithium batteries have advantages such as high energy density, small footprint, and long cycle life, and are expected to remain the mainstream in the market; however, their safety is very fragile, and in recent years, there have been several serious fire accidents caused by thermal runaway of lithium batteries. As battery charging and discharging speeds and energy densities increase, full immersion technology, which completely submerges the battery in insulating cooling oil, is becoming a key breakthrough and mainstream application for improving lithium battery safety. The immersion fluid can dissipate heat quickly and evenly, and effectively suppress fires. Immersion battery energy storage typically involves injecting immersion fluids (such as hydrocarbon synthetic oil, silicone oil, and fluorinated liquid) into IP67 sealed battery modules. However, over long-term operation, the insulation performance of the fluid may decline due to water ingress, aging, or contamination (such as leakage of electrolyte from the battery cells), significantly reducing its safety performance. Therefore, it is necessary to monitor the insulation status of the fluid online in real time, and notify maintenance personnel to handle any abnormalities and eliminate potential safety hazards.

[0015] Currently, the insulation performance testing of oils mostly adopts offline laboratory testing methods, which involves periodically sampling oil on-site and sending it to the laboratory for testing. Alternatively, portable instruments can be used to extract and test the oil on-site. However, both methods require on-site operation by professionals, and the testing costs are very high.

[0016] However, many data centers and energy storage sites are now edge nodes, deployed in locations that may be unattended or inaccessible. Furthermore, battery immersion fluids are hazardous industrial liquids, and to prevent evaporation or leakage, manufacturers typically design battery modules with IP67 sealing, making on-site disassembly and maintenance extremely difficult. Therefore, fully automated, unmanned, and low-cost online real-time monitoring technology has become a necessity. However, the accuracy of online monitoring is generally lower than that of dedicated instruments; improving the accuracy of online real-time monitoring is currently a major challenge facing the industry.

[0017] In addition, relevant documents require the new oil to have the following insulation properties: resistivity ρ ≥ 10⁹ Ω at room temperature. The dielectric strength (BDV) for the breakdown voltage (cm) should be ≥30kV, moisture content ≤50ppm, and dielectric loss factor (tanδ) ≤0.05. Resistivity (ρ) is the ability of the insulating medium to impede the directional movement of charge. It is a core parameter characterizing the purity, aging degree, and moisture content of the medium; a higher value indicates better insulation performance. If the value is below the threshold, it will lead to increased leakage current, intensified local heating, accelerated aging, and even short circuits. Key contributing factors include excessive moisture, accumulation of polar aging products, and solid impurity contamination, and it is significantly affected by temperature. Dielectric constant (ε) is a parameter characterizing the polarization ability of the insulating liquid, reflecting the medium's ability to store charge in an electric field. It is directly related to the electric field distribution and breakdown characteristics. The dielectric constant of the insulating liquid needs to be stable within a reasonable range (e.g., hydrocarbon synthetic oils are mostly between 2.0 and 2.3) to avoid electric field distortion with electrodes and air. If fluctuations exceed the range, it indicates medium contamination or aging, and the moisture and impurity content must be checked simultaneously.

[0018] However, real-time online detection of resistivity ρ remains a challenging problem in the industry. The resistivity ρ of insulating oil is extremely high. Typically, a specialized testing instrument is placed next to the operating equipment. A sample of the oil is poured into a three-electrode oil cup, and after precise temperature control in a constant temperature bath, pressure testing is performed. Another method is to add a high-precision electrode probe to each battery module, such as one with an electrode constant K of... A four-electrode probe can detect high-resistivity oils; however, high-precision electrode probes have small electrode spacing and large surface area, requiring very fine manufacturing and resulting in high individual costs. Clearly, while both methods achieve full automation and no manual operation, the systems are extremely complex and the hardware costs are very high, making them impractical for real-world engineering applications.

[0019] Figure 1This is a system architecture diagram of a Battery Management System (BMS) provided by relevant technologies. The BMS adopts a hierarchical, distributed, three-level control architecture. The bottom layer is configured with Battery Management Units (BMUs) to collect status data for single modules and single strings. Each battery cluster has a corresponding Battery Cluster Management Unit (BCMU) to complete the operation control and safety protection at the single battery cluster level. The units at each level communicate with each other via a Controller Area Network (CAN) to achieve highly reliable real-time data exchange between multiple nodes. All cluster-level data is uniformly aggregated upwards to the top-level Battery System Management Unit (BSMU), which enables overall system management and external communication scheduling. The system is equipped with a Human Machine Interface (HMI) as a local operation terminal, supporting on-site parameter configuration and intuitive display of operating status. Simultaneously, the top-level BSMU connects to the upper-level management system via Ethernet and utilizes RS-485 bus, CAN bus, and dry contact communication methods to achieve signal linkage and operational condition coordination with external power devices. The overall architecture achieves high-voltage safety isolation, distributed data acquisition, and centralized management through hierarchical control, and can be adapted to various energy storage application scenarios such as UPS power supply, communication base station backup power, and industrial and commercial energy storage.

[0020] This application provides a battery immersion fluid insulation testing device and a battery immersion fluid insulation testing method, aiming to realize online real-time testing of the insulation performance of immersion energy storage systems.

[0021] The battery immersion liquid insulation testing device provided in the embodiments of this application is described below with reference to the accompanying drawings.

[0022] Figure 2 This application provides a structure for a battery immersion fluid insulation testing device. Figure 1 .like Figure 2As shown, the battery immersion fluid insulation detection device provided in this application embodiment may include: a resistivity acquisition module 100, a dielectric constant acquisition module 200, an insulation impedance acquisition module 300, and a control module 400; wherein, the resistivity acquisition module 100 is disposed in the immersion fluid 500 of the battery module and is used to acquire the resistivity of the immersion fluid 500; the dielectric constant acquisition module 200 is disposed in the immersion fluid 500 and is used to acquire the dielectric constant of the immersion fluid 500; the insulation impedance acquisition module 300 is electrically connected to the battery cluster and is used to acquire the insulation impedance of the positive and negative electrodes of the battery cluster to ground, the battery cluster including multiple battery modules connected in series; the control module 400 is electrically connected to the resistivity acquisition module 100, the dielectric constant acquisition module 200, and the insulation impedance acquisition module 300 respectively, and is used to control the output of the immersion fluid insulation detection results based on the resistivity, dielectric constant, and insulation impedance.

[0023] In this embodiment, the resistivity acquisition module 100 and the dielectric constant acquisition module 200 respectively acquire the core electrical parameters of the immersion liquid 500, and the insulation impedance acquisition module 300 obtains the insulation impedance of the positive and negative electrodes of the battery cluster to ground. Then, the control module 400 integrates the three types of key parameters for collaborative analysis, which not only realizes the comprehensive acquisition of the electrical characteristics of the immersion liquid and the insulation state of the battery cluster, but also outputs the insulation detection results through multi-parameter fusion judgment, which greatly improves the comprehensiveness, accuracy and reliability of the battery immersion liquid insulation detection, and provides a strong guarantee for the safe operation of the battery module.

[0024] Figure 3 This application provides a structure for a battery immersion fluid insulation testing device. Figure 2 .like Figure 3 As shown, the battery cluster includes multiple battery modules connected in series. The battery modules are IP67 sealed. The battery modules contain battery cells 600. The immersion liquid 500 of the battery modules is hydrocarbon synthetic oil, silicone oil, fluorinated liquid, etc., and the immersion liquid 500 must completely submerge the battery cells 600 in the battery modules to ensure good cooling and fire protection effects.

[0025] The control module 400 of this application embodiment is applicable to a battery management system (BMS). In one exemplary implementation, the control logic of the control module 400 is executed collaboratively by the battery management unit (BMU), battery cluster management unit (BCMU), and battery system management unit (BSMU) of the BMS. It is understood that the specific implementation architecture of the control module 400 is not limited to this, and any other applicable architecture may be adopted.

[0026] like Figure 3As shown, the control module 400 includes: a battery management unit (BMU), a battery cluster management unit (BCMU), and a battery system management unit (BSMU); wherein, the battery management unit (BMU) is electrically connected to the resistivity acquisition module 100 and the dielectric constant acquisition module 200 located in the same battery module; the battery cluster management unit (BCMU) is electrically connected to multiple battery management units and the insulation impedance acquisition module 300, and is used to receive resistivity and dielectric constant uploaded by each battery management unit; the battery system management unit (BSMU) is electrically connected to at least one battery cluster management unit, and is used to receive resistivity, dielectric constant, and insulation impedance uploaded by each battery cluster management unit, and output the immersion liquid insulation detection results based on the resistivity, dielectric constant, and insulation impedance.

[0027] Specifically, the control module 400 is also used to control the dielectric constant acquisition module 200 to acquire the dielectric constant when the battery module is in a non-charging / discharging state. Understandably, when the battery module is in a non-charging / discharging state, the battery generates very little heat internally, and the immersion liquid 500 can fully exchange heat with the surrounding environment, making the temperature of the immersion liquid essentially the same as the ambient temperature. At this time, the temperature of the immersion liquid 500 is stable and does not fluctuate significantly, and temperature changes will not significantly interfere with the capacitance detection results, providing ideal detection conditions. Under this stable operating condition, the dielectric constant acquisition module 200 can accurately acquire the dielectric constant corresponding to the immersion liquid 500, providing accurate benchmark data for subsequent judgment of whether the immersion liquid 500 has abnormal conditions such as aging, contamination, leakage, or deterioration.

[0028] Specifically, such as Figure 3 As shown, the dielectric constant acquisition module 200 includes a capacitance detection unit 210 and a temperature sensor 220. The capacitance detection unit 210 is used to acquire the capacitance value of the immersion liquid 500. The temperature sensor 220 is located in the capacitance detection unit 210 and is used to acquire the temperature of the immersion liquid 500. The control module 400 is also used to perform temperature compensation on the capacitance value based on the temperature and determine the dielectric constant based on the compensated capacitance value. This effectively avoids the dielectric constant detection deviation caused by temperature fluctuations, thereby preventing the parameter changes caused by normal temperature changes from being mistakenly identified as abnormal conditions such as deterioration, aging, or contamination of the immersion liquid, and improving the accuracy and reliability of the immersion liquid status detection.

[0029] In one exemplary implementation, the capacitance detection unit 210 collects the capacitance value of the immersion liquid 500 in real time, and the temperature sensor 220 set in the capacitance detection unit 210 synchronously collects the real-time temperature of the immersion liquid 500 to ensure the time synchronization of the two sets of data. After receiving the above capacitance data and temperature data, the control module 400 can first perform filtering preprocessing on the two types of data to remove abnormal fluctuation components to avoid interference with the compensation accuracy and ensure the reliability of the basic data used for compensation. Then, based on the preset temperature-capacitance drift correspondence, the control module 400 queries and calculates the capacitance drift amount at the corresponding temperature according to the real-time temperature collected by the temperature sensor 220, and then performs reverse correction on the original capacitance value collected by the capacitance detection unit 210 to offset the drift deviation caused by temperature factors. Finally, the control module 400 calculates and determines the dielectric constant of the immersion liquid 500 based on the compensated capacitance value, effectively suppressing the dielectric constant detection deviation caused by temperature changes, avoiding misjudging parameter variations caused by temperature fluctuations as abnormal working conditions such as deterioration, aging or contamination of the immersion liquid, thereby improving the accuracy and reliability of immersion liquid status detection.

[0030] For example, such as Figure 3 As shown, two independent metal sheets are stacked at the edge of the immersion liquid 500 to form a capacitance detection unit 210. The immersion liquid 500 is used as the medium between the two independent metal sheets. By detecting the capacitance value of the immersion liquid 500, the dielectric constant corresponding to the immersion liquid 500 can be obtained.

[0031] In addition, two independent metal plates are double-fixed at both ends by insulating brackets 211, and the lead wires are wrapped with oil-resistant insulating heat shrink tubing. The two metal plates are parallel and vertical, with a stable and constant spacing. The metal plates can be made of 304 stainless steel or 316 stainless steel, and the spacing between the two metal plates can be 0.5~20mm. If the spacing is less than 0.5mm, the metal plates are prone to short circuits due to impurities in the immersion liquid. If the spacing is greater than 20mm, the capacitance value will be too small, resulting in a decrease in detection sensitivity. At the same time, the edges of the metal plates can be designed with rounded corners to reduce the adhesion of air bubbles and contaminants. In addition, the temperature sensor 220 is set on the metal plate near the battery management unit to collect the temperature of the immersion liquid 500.

[0032] The capacitance value C1 acquired by the capacitance detection unit 210 is calculated as C1 = ε*S / d. Here, ε is the dielectric constant, S is the area of ​​the two metal plates facing each other, and d is the distance between the two metal plates. A larger area S results in a larger capacitance value C1, and higher detection sensitivity and interference immunity. The plate area S and the distance d are adjusted to balance installation space and capacitance value.

[0033] Specifically, the control module 400 performs temperature compensation on the capacitance value based on the temperature of the immersion liquid 500. This corrects the capacitance value measured at a non-reference temperature to the capacitance value at the reference temperature, eliminating the interference of temperature changes on the dielectric constant detection results of the immersion liquid. Thus, the control module 400 determines the current dielectric constant of the immersion liquid based on the compensated capacitance value, using this as the core basis for judging the state of the immersion liquid. This effectively avoids the dielectric constant detection deviation caused by temperature fluctuations, thereby preventing normal temperature changes from being misidentified as abnormal conditions such as deterioration, aging, or contamination of the immersion liquid 500, and improving the accuracy and reliability of the immersion liquid state detection.

[0034] For example, the control module 400 performs temperature compensation on the capacitance value based on the temperature of the immersion liquid 500, and determines the dielectric constant based on the compensated capacitance value. The dielectric constant is calculated using the formula ε=C2*d / S, where C2 is the compensated capacitance value. Next, the dielectric constant is calibrated for deviation based on a preset calibration coefficient. Then, the temperature-compensated capacitance value is collected multiple times, and the dielectric constant corresponding to each of the multiple collected compensated capacitance values ​​is calculated and the average value is obtained. This effectively reduces the impact of random errors and interference, and further improves the accuracy and stability of the dielectric constant detection results.

[0035] The dielectric constant is compared with a set threshold. For example, when the dielectric constant is ≤105%, it is qualified; when the dielectric constant is ≤120%, it is slightly deteriorated (and a level 1 warning is generated); when the dielectric constant is ≤130%, it is moderately deteriorated (and a level 2 warning is generated); and when the dielectric constant is >130%, it is severely deteriorated (and an alarm is generated, requiring mandatory replacement).

[0036] like Figure 3 As shown, the Battery Monitoring Unit (BMU) includes a Microcontroller Unit (MCU) / Digital Signal Processor (DSP) and a Cell Data Acquisition Chip (CDC). The CDC is connected to the Capacitance Detection Unit 210 via a capacitance detection lead to receive the immersion fluid capacitance data collected by the Capacitance Detection Unit 210. The MCU / DSP is connected to the Temperature Sensor 220 via a temperature detection lead to receive the immersion fluid temperature data collected by the Temperature Sensor 220. The MCU / DSP is also communicatively connected to the CDC and configured to perform temperature compensation on the collected capacitance value based on the temperature of the immersion fluid 500, and then determine the dielectric constant of the immersion fluid 500 based on the compensated capacitance value.

[0037] like Figure 3As shown, the resistivity acquisition module 100 includes an electrode probe 110, which is connected to the MCU / DSP via an RS485 communication line.

[0038] For example, the electrode probe 110 can be an ultrapure water conductivity electrode. The resistivity in the immersion fluid 500 is detected by the ultrapure water conductivity electrode, and then the immersion fluid insulation test result is output through the resistivity to determine whether the immersion fluid 500 has deteriorated or needs to be replaced.

[0039] Electrode probe 110 can specifically adopt an electrode constant K of... The ultrapure water conductivity electrode has an effective resistivity measurement range of 100 kΩ. cm~1GΩ cm. Compared to The high-precision four-electrode detection probe, with an electrode constant K equal to that of ultrapure water conductivity electrodes, while having relatively insufficient detection accuracy, boasts a simple structure and low manufacturing cost, offering significant economic advantages. To ensure that the resistivity detection results of the immersion liquid meet the accuracy requirements under actual operating conditions while employing this type of low-cost electrode, this application combines the temperature and resistivity variation characteristics of the immersion liquid and adopts a method for resistivity detection under high-temperature battery operating conditions. Leveraging the significant resistivity changes, strong detection signal, and high resolution of the immersion liquid under high-temperature conditions, this method compensates for the inherent accuracy shortcomings of the ultrapure water conductivity electrode, thereby effectively improving the accuracy of resistivity detection and balancing detection economy and measurement reliability.

[0040] It should be understood that the resistivity testing under the aforementioned high-temperature operating conditions of the battery can be specifically achieved by controlling the battery to perform charging or discharging operations, and conducting resistivity testing when the battery is in a high-temperature state during the charging or discharging process. Specifically, the control module 400 is also used to control the battery module to perform charging or discharging, and to control the resistivity acquisition module 100 to acquire resistivity when the battery module is in a high-temperature state during charging or discharging.

[0041] Specifically, the high-temperature state during charging or discharging refers to the thermal state of the battery module at the end of the charging process, the end of the discharging process, or in the short period immediately after the charging or discharging process ends.

[0042] Understandably, the resistivity of the immersion fluid 500 decreases exponentially with increasing temperature, and the higher the temperature, the more significant the rate of resistivity change with temperature. When the battery undergoes high-rate charge and discharge operations, the immersion fluid temperature rises above 40°C. Within this temperature range, the resistivity rapidly and exponentially decays, allowing the ultrapure water conductivity electrode to obtain a sufficiently strong voltage signal and detection resolution. Specifically, this is particularly relevant in the low resistivity range (250 MΩ) corresponding to the gradual degradation of the immersion fluid 500 from its normal state to the point where it needs replacement. cm~100MΩ Within a range of cm, the ultrapure water conductivity electrode can still maintain optimal linearity and detection resolution, thereby effectively improving the accuracy and reliability of resistivity measurement results.

[0043] Specifically, the control module 400 is also used to perform temperature compensation on the resistivity according to the temperature of the immersion liquid 500, and control the resistivity acquisition module 100 to acquire the resistivity of the temperature-compensated immersion liquid 500, thereby outputting the immersion liquid insulation test result through the compensated resistivity to determine whether the immersion liquid 500 has deteriorated or needs to be replaced.

[0044] It is understandable that when the temperature of the immersion fluid 500 reaches a high temperature of 60°C or above, the resistivity of the immersion fluid 500 approaches 100 MΩ. The replacement threshold for cm; this is a normal change caused by temperature, not oil deterioration, therefore it needs to be compensated by a reference temperature of 20℃ or 25℃ to eliminate the influence of temperature, otherwise it will cause false alarms. At the same time, the resistivity measured in high-temperature environments also needs to be converted into the resistivity at the reference temperature through temperature compensation as a criterion for judging the oil insulation. Therefore, it can prevent parameter changes caused by normal temperature changes from being mistakenly identified as abnormal conditions such as deterioration, aging or contamination of the immersion fluid 500, thus improving the accuracy and reliability of immersion fluid condition detection.

[0045] For example, when the temperature of the immersion liquid 500 reaches a high temperature of 60°C or above, it is necessary to compensate for the temperature effect by using a reference temperature of 20°C or 25°C; after temperature compensation for resistivity, the resistivity acquisition module 100 is controlled to acquire the resistivity of the immersion liquid 500, and the resistivity is compared with a set threshold, for example, when the resistivity is ≥1 GΩ. cm is acceptable, resistivity ≤500MΩ cm indicates slight degradation (simultaneously triggering a Level 1 warning), resistivity ≤200MΩ cm indicates moderate degradation (with a secondary warning issued simultaneously), resistivity ≤100MΩ cm indicates severe degradation (an alarm will be generated, requiring shutdown or forced replacement).

[0046] Specifically, the control module 400 is also used to control the battery cluster to be in an open state and to control the insulation impedance acquisition module 300 to acquire insulation impedance in the open state; for example, the control module 400 controls the contactor or switch on the high voltage box to open so that the battery cluster is in an open state, thereby controlling the insulation impedance acquisition module 300 to acquire insulation impedance, and then closing the battery cluster after the detection is completed.

[0047] For example, Figure 4 This is a schematic diagram of the battery cluster structure provided in the embodiments of this application, such as... Figure 4As shown, there is a switch S1 on the side of the battery cluster with the positive terminal to ground, and a switch S2 on the side of the battery cluster with the negative terminal to ground. Additionally, there are two standard resistors, R1 and R2, on the sides of the battery cluster with the positive and negative terminals to ground, respectively. By alternately switching switches S1 or S2, the equivalent resistance of the two terminals to ground is changed, resulting in an unbalanced detection voltage across the positive and negative detection resistors. This allows the insulation resistance of the positive and negative terminals of the battery cluster to be calculated.

[0048] The specific control methods are as follows: Close S1, open S2, and collect the voltage at point U1 and the total voltage U; Close S2, open S1, and collect the voltage at point U2 and the total voltage U; Based on the equations Rx=(U*R2-(R1+R2)*(U1+U2)) / U1 and Ry=(U*R2-(R1+R2)*(U1+U2)) / U2, the insulation resistance Rx of the positive electrode and the insulation resistance Ry of the negative electrode of the battery cluster can be obtained. The insulation resistance Riso of the battery cluster is taken as the smaller value between the insulation resistance Rx of the positive terminal and the insulation resistance Ry of the negative terminal. That is, when the insulation resistance Rx of the positive terminal is less than the insulation resistance Ry of the negative terminal, the insulation resistance Riso of the battery cluster is equal to the insulation resistance Rx of the negative terminal. When the insulation resistance Rx of the positive terminal is greater than the insulation resistance Ry of the negative terminal, the insulation resistance Riso of the battery cluster is equal to the insulation resistance Ry of the negative terminal.

[0049] Based on the battery cluster system's operating voltage, balance measurement accuracy, and power consumption, standard resistors R1 and R2 can be selected as thin-film or metal foil resistors with an accuracy of over 1% and a temperature coefficient ≤ ±50ppm / ℃, ranging from 100kΩ to 1MΩ. Switches S1 and S2 can be solid-state relays with very low leakage current (e.g., ≤1μA) to ensure measurement accuracy.

[0050] When the insulation resistance Riso of the battery cluster is lower than the safety threshold (e.g., 1MΩ), it indicates a decline in the insulation health level. The cause may be a system structural fault (insulation damage to the wiring harness / connector, or insulation defects such as local creepage / arc). It may also be a problem with the deterioration of the immersion fluid 500 (e.g., water ingress / contamination / aging).

[0051] Based on the above-described battery immersion liquid insulation testing device, the battery immersion liquid insulation testing method provided in the embodiments of this application will be described below.

[0052] Please see Figure 5 , Figure 5 This is a flowchart illustrating a battery immersion fluid insulation testing method provided in an embodiment of this application. The battery immersion fluid insulation testing method provided in this embodiment includes the following steps: Step S101: Collect the dielectric constant and resistivity of the immersion liquid in the battery module, and collect the insulation impedance of the positive and negative terminals of the battery cluster to ground. The battery cluster includes multiple battery modules connected in series. Step S102: Based on resistivity, dielectric constant and insulation impedance, control the output of the immersion liquid insulation test results.

[0053] In one embodiment, the dielectric constant of the immersion fluid 500 is collected when the battery module is in a non-charging / discharging state. When the battery module is in a non-charging / discharging state, the internal heat generation of the battery is minimal, and the immersion fluid 500 can fully exchange heat with the surrounding environment, making the temperature of the immersion fluid basically consistent with the ambient temperature. At this time, the temperature of the immersion fluid 500 is stable and does not fluctuate significantly, and temperature changes will not significantly interfere with the capacitance detection results, providing ideal detection conditions. Under this stable operating condition, the dielectric constant of the immersion fluid 500 can be accurately collected, providing accurate benchmark data for subsequent judgment of whether the immersion fluid 500 has abnormal conditions such as aging, contamination, leakage, or deterioration.

[0054] In another embodiment, when the battery module is in a non-charging / discharging state, the dielectric constant of the immersion fluid 500 is collected multiple times, and the average value of the collected dielectric constants is taken as the dielectric constant. When the battery module is in a non-charging / discharging state, the internal heat generation of the battery is minimal, and the immersion fluid 500 can fully exchange heat with the surrounding environment, making the temperature of the immersion fluid basically consistent with the ambient temperature. At this time, the temperature of the immersion fluid 500 is stable and does not fluctuate significantly, and temperature changes will not significantly interfere with the capacitance detection results, providing ideal detection conditions. Under this stable operating condition, the dielectric constant corresponding to the immersion fluid 500 can be accurately collected, providing accurate benchmark data for subsequent judgment of whether the immersion fluid 500 has aging, contamination, leakage, or deterioration, or other abnormal conditions. In addition, by taking the average value of the collected dielectric constants as the dielectric constant, the influence of random errors and interference can be effectively reduced, further improving the accuracy and stability of the dielectric constant detection results.

[0055] Specifically, the capacitance value of the immersion liquid 500 is collected by the capacitance detection unit 210 and the temperature of the immersion liquid 500 is collected by the temperature sensor 220. The control module 400 performs temperature compensation on the capacitance value according to the temperature of the immersion liquid 500, so as to correct the capacitance value measured at a non-reference temperature to the capacitance value at the reference temperature, thereby determining the dielectric constant based on the compensated capacitance value.

[0056] Specifically, the control module 400 performs temperature compensation on the capacitance value based on the temperature of the immersion liquid 500, correcting the capacitance value measured at a non-reference temperature to the reference temperature. This eliminates the interference of temperature changes on the dielectric constant detection results of the immersion liquid, thereby determining the current dielectric constant of the immersion liquid 500 based on the compensated capacitance value. This serves as the core basis for judging the state of the immersion liquid, effectively avoiding dielectric constant detection deviations caused by temperature fluctuations. Furthermore, it prevents normal temperature changes from being mistakenly identified as abnormal conditions such as deterioration, aging, or contamination of the immersion liquid 500, thus improving the accuracy and reliability of immersion liquid state detection.

[0057] In one embodiment, after acquiring the dielectric constant, the dielectric constant can be calibrated based on a preset calibration coefficient to eliminate system offsets caused by hardware differences in the temperature sensor 220 and environmental interference. By introducing a calibration coefficient to correct the dielectric constant, measurement deviation can be significantly reduced, making the detection results closer to the true dielectric constant of the immersion liquid 500, further improving the consistency and reliability of subsequent state judgments, and providing more accurate data support for identifying the degree of degradation and providing early warning of deterioration of the immersion liquid 500.

[0058] In one embodiment, the battery module is controlled to perform charging or discharging, and the resistivity of the immersion fluid 500 is collected when the battery module is in a high-temperature state during charging or discharging. The resistivity of the immersion fluid 500 decreases exponentially with increasing temperature, and the higher the temperature, the more significant the rate of change in resistivity with temperature. When the battery is undergoing high-rate charging and discharging, the temperature of the immersion fluid rises above 40°C. Within this temperature range, the resistivity decays rapidly and exponentially, allowing the ultrapure water conductivity electrode to obtain a sufficiently strong voltage signal and detection resolution. Specifically, the resistivity range (250 MΩ) corresponds to the gradual deterioration of the immersion fluid 500 from its normal state to the state requiring replacement. cm~100MΩ Within a range of cm, the ultrapure water conductivity electrode can still maintain optimal linearity and detection resolution, thereby effectively improving the accuracy and reliability of resistivity measurement results.

[0059] In another embodiment, the battery module is controlled to charge or discharge, and the resistivity of the immersion fluid 500 is repeatedly collected while the battery module is in a high-temperature state during charging or discharging. The average resistivity of the collected resistivity is taken as the resistivity. The resistivity of the immersion fluid 500 decreases exponentially with increasing temperature, and the higher the temperature, the more significant the rate of change in resistivity with temperature. When the battery is subjected to high-rate charging and discharging, the temperature of the immersion fluid rises above 40°C. Within this temperature range, the resistivity decays rapidly and exponentially, allowing the ultrapure water conductivity electrode to obtain a sufficiently strong voltage signal and detection resolution. Specifically, the resistivity range (250 MΩ) corresponds to the gradual deterioration of the immersion fluid 500 from its normal state to the state requiring replacement. cm~100MΩ Within a range of cm, the ultrapure water conductivity electrode can still maintain optimal linearity and detection resolution, thereby effectively improving the accuracy and reliability of resistivity measurement results. In addition, by taking the average value of multiple resistivity measurements as the resistivity, the influence of random errors and interference can be effectively reduced, further improving the accuracy and stability of resistivity detection results.

[0060] Specifically, the control module 400 performs temperature compensation on the resistivity based on the temperature of the immersion liquid 500, and controls the resistivity acquisition module 100 to acquire the resistivity of the temperature-compensated immersion liquid 500. The immersion liquid insulation test result is then output based on the compensated resistivity to determine whether the immersion liquid 500 has deteriorated or needs to be replaced.

[0061] It is understandable that when the temperature of the immersion fluid 500 reaches a high temperature of 60°C or above, the resistivity of the immersion fluid 500 approaches 100 MΩ. The replacement threshold for cm; this is a normal change caused by temperature, not oil deterioration, therefore it needs to be compensated by a reference temperature of 20℃ or 25℃ to eliminate the influence of temperature, otherwise it will cause false alarms. At the same time, the resistivity measured in high-temperature environments also needs to be converted into the resistivity at the reference temperature through temperature compensation as a criterion for judging the oil insulation. Therefore, it can prevent parameter changes caused by normal temperature changes from being mistakenly identified as abnormal conditions such as deterioration, aging or contamination of the immersion fluid 500, thus improving the accuracy and reliability of immersion fluid condition detection.

[0062] In one embodiment, the control module 400 controls the battery cluster to be in an open state and controls the insulation impedance acquisition module 300 to acquire insulation impedance in the open state. For example, the control module 400 controls the contactor or switch on the high voltage box to be open so that the battery cluster is in an open state, thereby controlling the insulation impedance acquisition module 300 to acquire insulation impedance, and then closes the battery cluster after the detection is completed.

[0063] In another embodiment, when there are multiple battery clusters, the control module 400 sequentially controls each battery cluster to be in an open state, and controls the insulation impedance acquisition module 300 to acquire the insulation impedance corresponding to each battery cluster in the open state. For example, the control module 400 sequentially controls the contactor or switch on each high-voltage box to be open, so that each battery cluster is in an open state in sequence, thereby controlling the insulation impedance acquisition module 300 to acquire the insulation impedance corresponding to each battery cluster, and then sequentially closing each battery cluster after the detection is completed.

[0064] In one embodiment, the dielectric constant is collected when the battery module is in a non-charging / discharging state. If an anomaly is found in the dielectric constant, resistivity and insulation impedance are then collected. When the battery module is not charging / discharging, the 600-cell battery does not generate significant heat, and the immersion liquid temperature is essentially the same as the ambient temperature, resulting in minimal temperature interference. Therefore, the dielectric constant is collected, and if an anomaly is found (e.g., excessive dielectric constant change or a warning signal is generated), resistivity and insulation impedance are collected. By prioritizing dielectric constant detection and triggering resistivity and insulation impedance collection in case of anomalies, high-frequency detection across the entire range can be avoided, reducing system power consumption.

[0065] In another embodiment, the battery cluster is controlled to be in an off state under preset disconnection conditions, insulation impedance is collected, and resistivity acquisition is initiated when the insulation impedance is abnormal (e.g., excessive insulation impedance change or warning). By initiating resistivity acquisition when insulation impedance is abnormal, high-frequency detection across the entire range can be avoided, reducing system power consumption.

[0066] For example, the aforementioned preset disconnection conditions may be: a period during which the battery cluster can be safely disconnected (such as when the mains power is good, or when the battery capacity has redundant configuration and the timed measurement cycle has arrived), or when there is an application to measure the insulation impedance, or when the marker to be measured is in position.

[0067] In another embodiment, the battery module is controlled to charge or discharge under preset charging and discharging conditions, and resistivity is collected when the battery module is in a high-temperature state during charging or discharging. During the charging and discharging process, the battery module continuously generates heat internally, causing the immersion liquid temperature to rise significantly and enter a high-temperature operating range. At this time, the resistivity exhibits good detection sensitivity and signal resolution. The system simultaneously collects immersion liquid resistivity parameters, effectively improving the accuracy and reliability of the resistivity measurement results.

[0068] For example, the aforementioned preset charging and discharging conditions may be: a time when the battery module can be safely charged or discharged (such as when the battery is normal and there are no alarms such as overheating / overvoltage), or when there is an application to measure the resistivity of the immersion liquid, or when the target measurement flag is set.

[0069] The resistivity of the immersion fluid is generally measured at the end of the battery charge / discharge cycle or immediately after the charge / discharge cycle. This is because the battery module generates a lot of heat during charge / discharge (data center battery energy storage typically involves high-power charge / discharge, generating even more heat). Furthermore, at the end of the charge / discharge cycle, the temperature will briefly rise to its peak and then steadily decrease due to the combined effects of delayed Joule heat dissipation and brief side reactions. Therefore, the oil temperature is at its peak at the end of the charge / discharge cycle, making this the most accurate time to measure resistivity.

[0070] In one embodiment, for example, when resistivity, dielectric constant and insulation impedance are all normal, indicating no abnormal fluctuations in parameters, no exceeding limits or warning situations, it is determined that all physical and chemical properties and insulation properties of the immersion liquid meet the requirements for safe use, and the output of the immersion liquid insulation is normal.

[0071] For example, when resistivity, dielectric constant, and insulation impedance are all abnormal, it indicates that the problem is not simply a deterioration of the immersion medium. The overall insulation condition of the Battery Management System (BMS) is potentially compromised, and the control output of the battery storage system is showing abnormal results.

[0072] For example, if there is an abnormality in the insulation impedance but the resistivity and dielectric constant are normal, it indicates that the abnormality is not caused by the deterioration of the immersion liquid, and it is determined to be a structural insulation fault in the battery system, and the control output structural insulation fault result is controlled.

[0073] For example, when there are abnormalities in resistivity and dielectric constant, it indicates that the physical and chemical properties of the immersion liquid have deteriorated, and its core functions such as insulation and heat dissipation are affected, thus controlling the output of the immersion liquid deterioration results.

[0074] For example, when resistivity abnormally decreases and dielectric constant abnormally increases, it indicates that water has penetrated into and mixed with the immersion liquid. The high dielectric and low insulating properties of water alter the overall dielectric properties of the immersion liquid, thus allowing for precise identification of the immersion liquid ingress anomaly and control of the output immersion liquid ingress result. Understandably, water is a highly polar medium with a dielectric constant much greater than that of the immersion liquid. If water intrudes into the immersion liquid, it will significantly increase the overall equivalent dielectric constant of the mixed medium, thereby causing the abnormal increase in the dielectric constant of the immersion liquid.

[0075] For example, when the insulation impedance drops abnormally, the resistivity drops abnormally, and the dielectric constant fluctuates abnormally, it indicates that the overall dielectric performance of the immersion fluid 500 is severely degraded, the original insulation, heat dissipation and dielectric stability characteristics are lost, and it can no longer provide normal protection and cooling for the battery module, thus controlling the failure of the immersion fluid output.

[0076] For example, when the resistivity is decreasing and the dielectric constant is increasing, it indicates that the internal components of the immersion liquid 500 are slowly aging, impurities are gradually accumulating, the dielectric insulation performance is gradually deteriorating, the overall physical and chemical properties are continuously deteriorating, and the control output immersion liquid degradation results are affected.

[0077] For example, when the insulation impedance and resistivity are normal, but the dielectric constant drops abnormally, the output bubble interference result is controlled. Since the insulation impedance parameters are normal and the resistivity of the immersion liquid is stable within the normal range, with no abnormal deviations, and only the dielectric constant shows an abnormal drop, core fault factors such as immersion liquid 500 deterioration, water ingress, and structural insulation defects can be ruled out. The anomaly is determined to be caused by air bubbles mixed into the immersion liquid 500. The dielectric characteristics of the bubbles differ significantly from those of the immersion liquid 500 itself, interfering with the capacitance detection signal and leading to an abnormal drop in the dielectric constant detection value. Based on this, the detection conclusion of bubble interference is output, providing accurate guidance for staff to investigate the source of the bubbles and eliminate detection interference. Understandably, the dielectric constant of air is lower than that of the immersion liquid. When air bubbles are mixed into the immersion liquid, the overall equivalent dielectric constant of the mixed medium is lowered by the air component, resulting in an abnormal drop in the dielectric constant detection value of the immersion liquid.

[0078] The technical solutions provided in the embodiments of this application are illustrated below through specific examples.

[0079] Example 1 Please see Figure 6 , Figure 6 This is a schematic diagram of the overall process of a battery immersion fluid insulation testing method provided in an embodiment of this application.

[0080] I. Temperature testing and calibration before leaving the factory.

[0081] 1. Temperature deviation calibration. Each temperature sensor in the battery module is calibrated using automated testing tools. 2. Dielectric constant ε setting. A professional dielectric constant tester was used to measure the dielectric constant ε of the immersion solution under different temperatures. 3. Dielectric constant ε calibration. The battery module is placed in a high and low temperature alternating test chamber, and the measured ε values ​​at different temperatures are obtained through the BMU. The measured values ​​are then compared with the ε values ​​of the new oil at the same temperature to calibrate the measured values. The calibration deviation is saved to the electrically erasable programmable read-only memory (EEPROM) or other non-volatile memory on the battery energy storage system board.

[0082] II. Insulation testing during battery energy storage system operation.

[0083] 1. The entry conditions for measuring dielectric constant, insulation impedance and resistivity correspond to conditions A, B and C below, respectively.

[0084] (1) Condition A: When the battery is in a static state (at this time the battery is neither charging nor discharging, the temperature of the immersion liquid is close to the ambient temperature), and the timed measurement cycle has ended, the dielectric constant ε can be measured. (2) Condition B: The battery cluster can be safely disconnected during the period (such as when the mains power is good, or the battery capacity has redundant configuration, and the timed measurement cycle has arrived), or there is an application to measure the insulation impedance, or the target measurement flag is in position, so that the system insulation impedance Riso can be measured. (3) Condition C: When the battery is safe to charge or discharge (e.g., the battery is normal, there are no overheating / overvoltage alarms), or there is an application to measure the resistivity of the oil, or the measurement mark is in position, the resistivity ρ of the immersion fluid can be measured. The timing for measuring the resistivity of the immersion fluid is generally chosen at the end / just after the battery charging and discharging. Because the battery module generates a lot of heat during charging and discharging (data center battery energy storage is generally high-power charging and discharging, generating even more heat), and because at the end of charging and discharging, due to the combined effect of Joule heat dissipation delay and short-term side reactions, the temperature will rise to a peak for a short time and then drop steadily. Therefore, the oil temperature is at its peak at the end of charging and discharging, and the resistivity measurement is most accurate at this time.

[0085] 2. Based on the admission criteria of measuring three parameters, the insulation testing and judgment process is as follows: (1) When condition A is met, measure the dielectric constant ε. If the value of ε is abnormal (the change is too large or an early warning is generated), apply to measure the insulation impedance Riso and resistivity ρ (i.e., set the measurement flag). (2) When condition B is met, measure the insulation impedance Riso. If the Riso value is abnormal (the change is too large or an early warning is generated), apply to add resistivity ρ (i.e. set the target measurement flag). (3) When condition C is met, the BSMU issues a battery charging or discharging command and measures the resistivity ρ at the end of the battery charging or discharging period. (4) After measuring the insulation impedance Riso, resistivity ρ, and dielectric constant ε, cross-validate and make a comprehensive judgment. For example: When resistivity, dielectric constant and insulation impedance are all normal, it indicates that there are no abnormal fluctuations in parameters, no exceeding limits or warning situations. It is determined that the physical and chemical properties and insulation properties of the immersion liquid 500 meet the requirements for safe use, and the control output shows that the insulation of the immersion liquid is normal. When resistivity, dielectric constant, and insulation impedance are all abnormal, it indicates that the problem is not simply a deterioration of the immersion medium. There are hidden dangers in the overall insulation state of the battery energy storage system, and the control output battery energy storage system has abnormal results. When there is an abnormality in the insulation impedance, but the resistivity and dielectric constant are normal, it indicates that the abnormality is not caused by the deterioration of the immersion liquid. It is determined to be a structural insulation fault in the battery system, and the control output is a structural insulation fault result. When there are abnormalities in resistivity and dielectric constant, it indicates that the physical and chemical properties of the immersion fluid 500 have deteriorated, and its core functions such as insulation and heat dissipation are affected. The control output shows the deterioration result of the immersion fluid. When resistivity decreases abnormally and dielectric constant increases abnormally, it indicates that water has penetrated into and mixed with the immersion liquid 500. The high dielectric and low insulating properties of water itself change the overall dielectric properties of the immersion liquid 500. This allows for accurate identification of abnormal water ingress faults in the immersion liquid 500 and control of the output immersion liquid ingress results. It is understandable that water is a highly polar medium with a dielectric constant much greater than that of the immersion liquid. If water enters the immersion liquid, it will significantly increase the overall equivalent dielectric constant of the mixed medium, thus causing the phenomenon of abnormal increase in the dielectric constant of the immersion liquid.

[0086] When the insulation impedance, resistivity and dielectric constant drop abnormally, it indicates that the overall dielectric performance of the immersion fluid 500 is severely degraded, the original insulation, heat dissipation and dielectric stability characteristics are lost, and it can no longer provide normal protection and cooling for the battery module, thus controlling the output immersion fluid failure result. When the resistivity decreases and the dielectric constant increases, it indicates that the internal components of the immersion liquid 500 are slowly aging, impurities are gradually accumulating, the dielectric insulation performance is gradually deteriorating, the overall physical and chemical properties are continuously deteriorating, and the output immersion liquid degradation results are controlled. When insulation impedance and resistivity are normal, but the dielectric constant drops abnormally, the output bubble interference result is controlled. Since the insulation impedance parameters are normal and the resistivity of the immersion fluid is stable within the normal range, with no abnormal deviations, and only the dielectric constant shows an abnormal drop, core fault factors such as immersion fluid 500 deterioration, water ingress, and structural insulation defects can be ruled out. The anomaly is determined to be caused by air bubbles mixed within the immersion fluid 500. The dielectric characteristics of the bubbles differ significantly from those of the immersion fluid 500 itself, interfering with the capacitance detection signal and leading to an abnormal drop in the dielectric constant detection value. Based on this, the bubble interference detection conclusion is output, providing precise guidance for staff to investigate the source of the bubbles and eliminate detection interference. Understandably, the dielectric constant of air is lower than that of the immersion fluid. When air bubbles are mixed into the immersion fluid, the overall equivalent dielectric constant of the mixed medium is lowered by the air component, resulting in an abnormal drop in the dielectric constant detection value of the immersion fluid.

[0087] For details, please see Figure 7 , Figure 7 This is a schematic diagram of a dielectric constant acquisition process provided in an embodiment of this application.

[0088] Measuring the dielectric constant ε using the capacitance method can help determine the quality of immersion solution 500. The impurities produced during the aging of water and immersion solution 500 are highly polar, which will significantly increase the dielectric constant ε of immersion solution 500.

[0089] Temperature acquisition and temperature compensation: Temperature acquisition: Multiple temperature sensors 220 are deployed in the middle and around the electrode plate to measure the oil temperature and correct for thermal expansion and contraction of the electrode plate; Temperature compensation: The collected capacitance value is compensated for temperature (or the capacitance-temperature correction formula is fitted by software) to correct the capacitance value C; to avoid temperature changes being misjudged as oil deterioration.

[0090] Insulation performance assessment: Calculate the ε value: Based on the temperature-compensated measurement capacity C, ε is calculated using the formula ε=C*d / S; then, deviation calibration is performed; finally, the average value is obtained by multiple data acquisitions to improve the accuracy of the measurement. Threshold determination and maintenance recommendations: ε≤105% is acceptable, ε≤120% is slight degradation (and generates a Level 1 warning), ε≤130% is moderate degradation (and generates a Level 2 warning), and ε>130% is severe degradation (and generates an alarm, requiring mandatory replacement).

[0091] For details, please see Figure 8 , Figure 8 A schematic flowchart of an insulation impedance acquisition method provided in this application embodiment. Figure 1 .

[0092] Insulation testing of battery energy storage systems. Battery energy storage systems typically consist of multiple battery clusters. The insulation testing process for the entire system is as follows: disconnect each battery cluster sequentially (e.g., disconnect the contactor or switch on the BCMU control high-voltage box), test the insulation resistance of that cluster, and then close the battery cluster again after the test is completed. Insulation assessment: If the Riso of a battery cluster is lower than the safety threshold (e.g., 1MΩ), it indicates a decline in the insulation health level. The cause may be a system structural fault (insulation damage to the wiring harness / connector, or insulation defects such as local creepage / arc). It may also be a problem with the deterioration of the immersion fluid 500 (e.g., water ingress / contamination / aging).

[0093] For details, please see Figure 9 , Figure 9 A schematic flowchart of an insulation impedance acquisition method provided in this application embodiment. Figure 2 .

[0094] The insulation impedance of the battery cluster is determined using the classic bridge method. (See attached diagram.) Figure 4Each side of the battery cluster's positive and negative terminals relative to ground has either a switch S1 or S2, and two standard resistors R1 and R2 with known resistance values. By alternately switching switches S1 or S2, the equivalent resistance of the two terminals relative to ground is changed, resulting in an unbalanced detection voltage across the positive and negative detection resistors, thereby allowing the insulation resistance of the battery's positive and negative terminals to be calculated.

[0095] Close S1, open S2, and collect the voltage at point U1 and the total voltage U; Close S2, open S1, and collect the voltage at point U2 and the total voltage U; Based on the equations Rx=(U*R2-(R1+R2)*(U1+U2)) / U1 and Ry=(U*R2-(R1+R2)*(U1+U2)) / U2, we can obtain the total positive ground Rx and the total negative ground Ry. The insulation resistance Riso is the smaller of Rx and Ry. Design Reference: Based on the battery cluster system's operating voltage, balancing measurement accuracy and power consumption, the recommended values ​​for standard resistors R1 and R2 are between 100kΩ and 1MΩ. It is suggested to use thin-film resistors or metal foil resistors with an accuracy of 1% or higher and a temperature coefficient ≤ ±50ppm / ℃. For switches S1 and S2, it is recommended to select solid-state relays with very low leakage current (e.g., ≤1μA) to ensure measurement accuracy. Insulation assessment: If the Riso of the battery cluster is lower than the safety threshold (e.g., 1MΩ), it indicates a decline in the insulation health level. The cause may be a system structural fault (insulation damage to the wiring harness / connector, or insulation defects such as local creepage / arc). It may also be a problem of fluid deterioration (e.g., water ingress / contamination / aging).

[0096] For details, please see Figure 10 , Figure 10 This is a schematic diagram of a resistivity acquisition process provided in an embodiment of this application.

[0097] First, the current remaining battery charge (State of Charge, SOC) is calculated. Then, based on the obtained SOC value, a threshold judgment is performed. If the battery SOC is greater than 80%, the battery discharge program is triggered and the discharge operation is started; otherwise, the battery charging program is started and the charging operation is performed. After the charging or discharging process is started, the system continuously monitors and judges the charging and discharging process. If it is determined that the charging and discharging process has not yet ended, the current operating condition is maintained. After the complete charging and discharging process is detected, the resistivity ρ of the immersion fluid 500 is collected.

[0098] Resistivity ρ detection: The resistivity ρ is measured using an ultrapure water electrode conductivity sensor. The insulation performance is determined based on the ρ value to determine whether the immersion solution 500 has deteriorated or needs to be replaced.

[0099] Measuring the resistivity ρ of the immersion fluid in a high-temperature environment: During high-rate charging and discharging of the battery, the temperature of the immersion fluid rises above 40°C, causing the resistivity ρ to decrease exponentially. At this point, a 0.01 electrode sensor provides sufficient voltage signal and resolution. In particular, the immersion fluid maintains optimal linearity and resolution from normal to deteriorated, and then to the low-resistivity range where replacement is needed, resulting in more accurate and reliable measurement results.

[0100] Temperature compensation: At temperatures above 60℃, the resistivity ρ of the immersion fluid approaches 100 MΩ. The replacement threshold for cm is a normal change caused by temperature, not a sign of immersion fluid deterioration. It must be compensated for using a reference temperature of 20°C or 25°C to eliminate the temperature effect; otherwise, false alarms will occur. Simultaneously, the resistivity measured in high-temperature environments also needs to be converted to the resistivity at the reference temperature through temperature compensation to determine the oil's insulation properties.

[0101] Insulation performance assessment: The measured resistivity is converted to a reference temperature and compared with a set threshold. For example, if the ρ value is ≥ 1 GΩ... cm is acceptable, ρ value ≤ 500MΩ cm indicates slight degradation (simultaneously triggering a Level 1 warning), ρ value ≤ 200 MΩ cm indicates moderate degradation (with a level 2 warning issued simultaneously), ρ value ≤ 100 MΩ cm indicates severe degradation (an alarm will be generated, requiring shutdown or forced replacement).

[0102] It is understood that the embodiments of this application have the following beneficial effects: 1. Extremely Low Cost: Among the various indicators for evaluating the insulation performance of immersion liquids, resistivity is a core parameter characterizing the purity and aging degree of the medium. Currently, the industry generally relies on professional testing instruments or high-precision probes, which are extremely costly. This application utilizes the heat generation characteristics of battery charging and discharging and temperature compensation technology to achieve the detection of immersion liquid resistivity through ultrapure water conductivity electrodes, reducing hardware costs by more than an order of magnitude, making online insulation testing feasible for large-scale applications. 2. Extremely high reliability: It integrates the system bridge impedance method, four-electrode resistivity method and capacitance dielectric constant method, with each step progressive and mutually corroborating, to achieve comprehensive, accurate and reliable online monitoring of oil health status; and can identify interference factors such as air bubbles to avoid false alarms; 3. Root cause identification: This application independently measures three parameters of the system insulation impedance, resistivity and dielectric constant, and performs cross-verification and fusion judgment, which can accurately locate various root causes such as structural failure, water ingress of immersion fluid, immersion fluid failure and aging of immersion fluid, so as to facilitate users to quickly solve the fault and improve the availability of battery energy storage system. 4. Enhanced safety: Periodic measurement of dielectric constant and system impedance, with additional resistivity measurement for verification when anomalies are detected, allows for immediate detection of emergencies such as water ingress into the immersion liquid, notifying users to handle the situation promptly and preventing the escalation of the fault or the occurrence of safety accidents such as electric shock. 5. Intelligent Operation and Maintenance: Periodically collect system impedance, resistivity and dielectric constant, and analyze the changes in data to detect sudden situations such as water ingress into the oil, and identify trends such as aging and deterioration of the immersion fluid. It can also provide early warnings, deterioration alarms and oil replacement alarms, making it convenient for users to respond flexibly, improve efficiency and reduce costs.

[0103] Example 2 The battery energy storage system is used indoors in the intelligent computing center, where the ambient temperature is 20℃~30℃. Each cabinet of the system provides 360kW of backup power for 10 minutes. Each cluster contains two battery clusters, supporting ±400V and 800V backup power, and can support up to eight cabinets in parallel. In addition to the battery modules, the battery cabinet also includes a high-voltage box and a three-level BMS system (the BMU is built into the battery module, the BCMU is built into the high-voltage box, and the BSMU is externally located on the cabinet door; the BSMU is equipped with a Human Machine Interface (HMI) for local interaction, and also has Ethernet / RS485 / (Controller Area Network, CAN) communication lines for connection to a high-voltage direct current (HVDC) power supply or a centralized management system). The battery modules are nominally 64V and consist of 20 high-stability, high-rate lithium iron phosphate cells connected in series, supporting a maximum of 6C continuous discharge and 3C charging. To ensure safe indoor operation, the cabinet is equipped with temperature / smoke / gas detection / aerosol fire suppression systems and uses submersible battery modules. The battery module adopts an IP67 protection rating design with separate internal and external cavities. The battery cell 600 and immersion fluid 500 are located in the internal cavity, while the BMU is in the external cavity. The module height is approximately 20cm. The immersion fluid 500 is a hydrocarbon synthetic oil. After completely submerging the battery cell 600, the liquid level is approximately 15cm, achieving rapid and uniform cooling and precise fire suppression.

[0104] To achieve the measurement of system insulation impedance, a classic unbalanced bridge circuit was added to each BCMU unit. Standard resistors R1 and R2 were selected as 220KΩ precision resistors, and switches S1 and S2 were selected as solid-state relays with leakage current less than 1μA. During testing, the BCMU disconnected the contactor on the high-voltage box; these multiple measures together ensured the accuracy of the system insulation impedance measurement.

[0105] To measure the resistivity ρ of the immersion fluid, a 0.01 ohm ultrapure water conductivity electrode, commonly used in power plants and water quality monitoring, was selected as the sensor. This electrode features a built-in mV-level AC drive, exhibiting low polarization drift resistance. The electrode material can be selected from titanium, 316 stainless steel, Hastelloy, etc., providing a permeability-resistant conductive surface suitable for harsh environments and long-term applications. The electrode dimensions are 120x20mm, and it is fixedly installed at the edge of the oil solution, with the probe immersed at least 10cm below the oil level. The shielding wire and battery module are connected to ground at a common point. The BMU connects to the electrode via an RS485 interface and obtains the temperature-compensated water temperature and resistivity values ​​via the Modbus RTU protocol.

[0106] To measure the dielectric constant ε of the immersion fluid, a capacitance method was employed. Two 316L stainless steel plates served as the plates of a planar capacitor, fixed at both ends by a PTFE-insulated bracket. The plates were immersed in the oil, parallel and vertical, with rounded edges. The leads were wrapped with oil-resistant insulating heat-shrink tubing. The plate spacing was 1.5 mm, the plate length was 134 mm, the width was 45 mm, and the area was approximately 60 cm². 2 For example, if the ε value of the hydrocarbon synthesis immersion solution is 2.2, the design baseline capacitance C of the parallel plate capacitor is approximately 78 pF. If ε increases from 2.2 to 2.3, the capacitance C will increase proportionally by approximately 3.5 pF. Therefore, the high-precision Capacitance-to-Digital Converter (CDC) chip AD7746 is selected, with a resolution of 0.01 pF, to accurately capture minute changes in capacitance. Multiple NTC temperature sensors 220 are deployed in the center and periphery of the plates to correct for thermal expansion and contraction of the plates and to provide temperature compensation for the measured capacitance value.

[0107] Through the above methods and steps, a detection circuit for three parameters—system insulation impedance, oil resistivity, and dielectric constant—was implemented.

[0108] Finally, the BMS system is run. The dielectric constant ε measurement cycle is set to 1 minute, and the insulation impedance Riso measurement cycle is set to 6 hours, according to requirements. The dielectric constant ε is measured when the access condition A of Example 1 is met; if ε is abnormal, an additional measurement of insulation impedance and resistivity is requested. The insulation impedance Riso is measured when the access condition B of Example 1 is met; if Riso is abnormal, an additional measurement of resistivity is requested. The resistivity ρ is measured when the access condition C of Example 1 is met. Finally, the insulation test result of the immersion fluid is comprehensively judged based on the three measurement values. Therefore, online monitoring of the immersion fluid health status of 500°C is achieved, greatly improving the safety of battery energy storage system operation; at the same time, it provides users with precise operation and maintenance guidance, significantly reducing operation and maintenance costs.

[0109] In summary, this application implements a low-cost resistivity detection method that integrates the detection of dielectric constant and system insulation impedance, thereby achieving comprehensive and reliable online real-time monitoring of the battery system's insulation status and the health of the immersion fluid. Its ingenious, unique, simple, and practical approach significantly improves the long-term reliability and safety of the equipment and system. Furthermore, by providing trend analysis and early warning, it offers precise operation and maintenance guidance, greatly reducing maintenance costs.

[0110] This application also provides an electronic device, which includes: at least one processor; at least one memory for storing at least one program; the at least one program is executed by the at least one processor to implement the battery immersion fluid insulation detection method of any of the foregoing embodiments.

[0111] A processor can be an integrated circuit chip with signal processing capabilities, such as a general-purpose processor, a digital signal processor (DSP), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. Among them, a general-purpose processor can be a microprocessor or any conventional processor.

[0112] The memory includes volatile memory or non-volatile memory, or both. Non-volatile memory may be read-only memory (ROM), and volatile memory may be random access memory (RAM). The memory described in the embodiments of this application is intended to include any suitable type of memory. The memory may optionally include one or more storage devices physically located away from the processor.

[0113] This application provides a computer program product, which includes a computer program or computer-executable instructions stored in a computer-readable storage medium. The processor of an electronic device reads the computer-executable instructions from the computer-readable storage medium and executes the computer-executable instructions, causing the electronic device to perform the battery immersion fluid insulation detection method described above in this application.

[0114] This application provides a computer-readable storage medium storing computer-executable instructions or computer programs. When the computer-executable instructions or computer programs are executed by a processor, the processor will execute the battery immersion liquid insulation detection method provided in this application.

[0115] In some embodiments of this application, the computer-readable storage medium may be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), flash memory, magnetic surface memory, optical disk, or CD-ROM, etc.; or it may be various devices including one or any combination of the above-mentioned memories.

[0116] In some embodiments of this application, computer-executable instructions may take the form of programs, software, software modules, scripts, or code, written in any form of programming language (including compiled or interpreted languages, or declarative or procedural languages), and may be deployed in any form, including being deployed as stand-alone programs or as modules, components, subroutines, or other units suitable for use in a computing environment.

[0117] As an example, computer-executable instructions may, but do not necessarily, correspond to files in a file system. They may be stored as part of a file that holds other programs or data, for example, in one or more scripts in a HyperText Markup Language (HTML) document, in a single file dedicated to the program in question, or in multiple co-located files (e.g., files that store one or more modules, subroutines, or code sections).

[0118] As an example, computer-executable instructions can be deployed to execute on a single electronic device, or on multiple electronic devices located at one location, or on multiple electronic devices distributed across multiple locations and interconnected via a communication network.

[0119] The above are merely embodiments of this application and are not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, and improvements made within the spirit and scope of this application are included within the scope of protection of this application.

Claims

1. A battery immersion fluid insulation testing device, characterized in that, include: A resistivity acquisition module is installed in the immersion liquid of the battery module to acquire the resistivity of the immersion liquid; A dielectric constant acquisition module is installed in the immersion liquid and is used to acquire the dielectric constant of the immersion liquid; An insulation impedance acquisition module is electrically connected to the battery cluster and is used to acquire the insulation impedance of the positive and negative terminals of the battery cluster to ground. The battery cluster includes multiple battery modules connected in series. The control module is electrically connected to the resistivity acquisition module, the dielectric constant acquisition module, and the insulation impedance acquisition module, respectively, and is used to control the output of the immersion liquid insulation detection result based on the resistivity, the dielectric constant, and the insulation impedance.

2. The apparatus according to claim 1, characterized in that, The control module is also used to control the dielectric constant acquisition module to acquire the dielectric constant when the battery module is in a non-charging / discharging state.

3. The apparatus according to claim 1, characterized in that, The dielectric constant acquisition module includes: A capacitance detection unit is used to collect the capacitance value of the immersion liquid; A temperature sensor, located in the capacitance detection unit, is used to collect the temperature of the immersion liquid; The control module is also used to perform temperature compensation on the capacitance value based on the temperature, and to determine the dielectric constant based on the compensated capacitance value.

4. The apparatus according to claim 1, characterized in that, The control module is also used to control the battery module to perform charging or discharging, and to control the resistivity acquisition module to acquire the resistivity when the battery module is in a high-temperature state during charging or discharging.

5. The apparatus according to claim 4, characterized in that, The resistivity acquisition module includes an electrode probe, which is an ultrapure water conductivity electrode.

6. The apparatus according to claim 4, characterized in that, The control module is also used to perform temperature compensation on the resistivity based on the temperature of the immersion liquid.

7. The apparatus according to claim 1, characterized in that, The control module is also used to control the battery cluster to be in a disconnected state, and to control the insulation impedance acquisition module to acquire the insulation impedance in the disconnected state.

8. The apparatus according to claim 1, characterized in that, The control module includes: The battery management unit is electrically connected to the resistivity acquisition module and the dielectric constant acquisition module, which are located in the same battery module. A battery cluster management unit is electrically connected to multiple battery management units and the insulation impedance acquisition module, and is used to receive the resistivity and dielectric constant uploaded by each of the battery management units; A battery system management unit, electrically connected to at least one of the battery cluster management units, is used to receive the resistivity, dielectric constant, and insulation impedance uploaded by each battery cluster management unit, and output the immersion liquid insulation detection result based on the resistivity, dielectric constant, and insulation impedance.

9. A method for testing the insulation of a battery immersion fluid, characterized in that, The method includes: The dielectric constant and resistivity of the immersion liquid in the battery module are collected, and the insulation impedance of the positive and negative electrodes of the battery cluster to ground is collected. The battery cluster includes multiple battery modules connected in series. Based on the resistivity, dielectric constant, and insulation impedance, the output of the immersion liquid insulation test result is controlled.

10. The method according to claim 9, characterized in that, The process of acquiring the dielectric constant includes: The dielectric constant of the immersion liquid is collected when the battery module is in a non-charging / discharging state. or, When the battery module is in a non-charging / discharging state, the dielectric constant of the immersion liquid is collected multiple times, and the average value of the collected dielectric constants is taken as the dielectric constant.

11. The method according to claim 10, characterized in that, The dielectric constant is determined based on the capacitance value of the immersion liquid; The capacitance value is obtained through the following process: The temperature and capacitance of the immersion liquid were collected; The capacitance value is compensated for based on the temperature to obtain the compensated capacitance value.

12. The method according to any one of claims 9-11, characterized in that, After acquiring the dielectric constant, the process also includes: The dielectric constant is calibrated based on a preset calibration coefficient.

13. The method according to claim 9, characterized in that, The resistivity acquisition process includes: The battery module is controlled to perform charging or discharging, and the resistivity of the immersion liquid is collected when the battery module is in a high-temperature state during charging or discharging. or, The battery module is controlled to charge or discharge, and the resistivity of the immersion liquid is collected multiple times when the battery module is in a high-temperature state during charging or discharging. The average value of the multiple collected resistivity is taken as the resistivity.

14. The method according to claim 9 or 13, characterized in that, After acquiring the resistivity, the process also includes: The temperature of the immersion liquid was collected; The resistivity is temperature-compensated based on the temperature to obtain the compensated resistivity.

15. The method according to claim 9, characterized in that, The process of collecting the insulation impedance of the positive and negative terminals of the battery cluster to ground includes: The battery cluster is controlled to be in an off state, and in the off state, the insulation impedance of the positive and negative terminals of the battery cluster to ground is collected.

16. The method according to claim 15, characterized in that, The battery clusters are multiple, and the method further includes: sequentially controlling each battery cluster to be in a disconnected state in order to collect the insulation impedance corresponding to each battery cluster.

17. The method according to claim 16, characterized in that, The dielectric constant and resistivity of the immersion fluid in the battery module are collected, and the insulation impedance of the positive and negative terminals of the battery cluster to ground is collected, including at least one of the following: When the battery module is in a non-charging / discharging state, the dielectric constant is collected, and if the dielectric constant is abnormal, the resistivity and insulation impedance are collected. Under preset disconnection conditions, the battery cluster is controlled to be in a disconnected state, the insulation impedance is collected, and if the insulation impedance is abnormal, the resistivity is collected. The battery module is controlled to charge or discharge under preset charging and discharging conditions, and the resistivity is collected when the battery module is in a high-temperature state during charging or discharging.

18. The method according to claim 9, characterized in that, Based on the resistivity, the dielectric constant, and the insulation impedance, the output of the immersion liquid insulation test result is controlled to include at least one of the following: When the resistivity, dielectric constant, and insulation impedance are all normal, the output of the immersion liquid is controlled to achieve normal insulation results. When the resistivity, dielectric constant, and insulation impedance are all abnormal, the control output battery energy storage system will produce abnormal results. When the insulation impedance is abnormal, but the resistivity and dielectric constant are normal, the control outputs the structural insulation fault result. In the event of abnormalities in the resistivity and dielectric constant, the deterioration result of the immersion solution is controlled and output. When the resistivity abnormally decreases and the dielectric constant abnormally increases, the output of the immersion liquid water inlet result is controlled. When the insulation impedance drops abnormally, the resistivity drops abnormally, and the dielectric constant fluctuates abnormally, the immersion liquid failure result is output. When the resistivity shows a decreasing trend and the dielectric constant shows an increasing trend, the output immersion liquid degradation result is controlled. When the insulation impedance and resistivity are normal, but the dielectric constant drops abnormally, the output bubble interference result is controlled.

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