Battery management system and control method thereof

Abstract

The application relates to the technical field of battery management, and discloses a battery management system and a control method thereof. The system comprises a battery module, a busbar and a BMS circuit board, the busbar is provided with a threaded hole, the BMS circuit board is provided with a through hole, a screw is screwed into the threaded hole through the through hole to directly fix the BMS circuit board on the busbar, the screw simultaneously serves as a voltage sampling contact and electrically contacts the busbar, and a voltage sampling module collects monomer battery voltage signals through the screw and the busbar. The control method comprises the following steps: acquiring electrical characteristic parameters of each screw and busbar connection point, comparing the electrical characteristic parameters with initial reference values to judge the connection state and determine the abnormality degree, and executing a hierarchical control strategy according to the abnormality degree. The application omits a traditional voltage collection wire harness, simplifies the structure, is compatible with general batteries on the market, simultaneously realizes active monitoring and hierarchical control of the screw connection state, and improves the safety and reliability of the system.

Description

Technical Field

[0001] This invention relates to the field of battery management technology, and in particular to a battery management system and its control method. Background Technology

[0002] Currently, light electric vehicles such as two-wheeled and three-wheeled vehicles generally use lithium battery packs for power supply. The BMS (Battery Management System) circuit board, as the core control component of the battery pack, is mainly responsible for basic functions such as battery parameter acquisition, charge and discharge protection, and battery balancing. The connection structure between the BMS and the battery module directly affects the overall vehicle assembly cost, sampling stability, and electrical safety.

[0003] Currently, the assembly methods for BMS and battery modules are mostly welding, crimping, or wire harness connectors. Among these, the assembly structure of wire harness connectors has a large number of components, a complicated assembly process, and a relatively high overall cost. Moreover, the mixed routing of high and low voltage lines can easily cause interference, and the requirements for system insulation and safety protection are high. To improve the problem of complex wire harness structures, the industry has gradually adopted a screw-locking assembly method, which directly fixes the BMS board to the battery terminals or busbars. At the same time, the screws are used to achieve voltage sampling, thereby eliminating the need for external sampling wire harnesses and simplifying the assembly structure.

[0004] For example, in existing technologies, threaded holes are directly machined into the battery terminals, and the BMS board is locked and fixed to the battery terminals with screws, relying on the conduction of the screws to achieve voltage sampling. Although this structure eliminates the need for wiring harnesses, it has the following problems in practical applications: First, the threaded holes are directly machined into the battery terminals, and the terminals of conventional mass-produced batteries on the market do not have a pre-set thread structure. When integrating and assembling batteries, only custom-made batteries can be used, resulting in poor versatility. Second, battery terminals are mostly made of soft aluminum material. After long-term bumps and vibrations in the vehicle or repeated disassembly and assembly, the threads of the terminals are very prone to stripping and failure. After the terminals are damaged, they cannot be repaired separately, and the entire battery module must be replaced, resulting in extremely high maintenance costs. Third, this structure does not have a screw loosening detection mechanism designed for vehicle vibration conditions, and cannot identify screw loosening or poor connection, posing a safety hazard.

[0005] In addition, a few solutions in the industry can detect loose screws, but they only have basic detection and abnormal alarm functions. The detection results only indicate the fault and do not integrate with the core functions of BMS such as voltage sampling calibration, battery balancing, and charging and discharging power control for linkage regulation.

[0006] In summary, there is currently no perfect technical solution that can simultaneously accommodate universal battery compatibility, simplify BMS assembly structure, monitor screw connection status in real time, and implement hierarchical closed-loop control based on the degree of loosening. Summary of the Invention

[0007] The main objective of this invention is to provide a battery management system and its control method, which aims to solve the technical problems of existing technologies being incompatible with commercially available general-purpose batteries, simplifying the BMS integration structure, and failing to actively address screw loosening issues, as well as dynamically associating connection status detection with BMS control strategies.

[0008] To achieve the aforementioned objectives, the first aspect of this invention provides a battery management system for use in a light electric vehicle, comprising: A battery module is composed of multiple individual batteries, and a busbar is fixedly connected to the terminal of each individual battery. The BMS circuit board integrates a voltage sampling module; The busbar has a threaded hole, and the BMS circuit board has a corresponding through hole. The BMS circuit board is positioned above the busbar. A screw passes through the through hole and is screwed into the threaded hole to directly fix the BMS circuit board to the busbar. The screw also serves as a voltage sampling contact and makes electrical contact with the busbar. The voltage sampling module collects the voltage signal of the individual battery through the screw and the busbar.

[0009] A second aspect of the present invention provides a control method for a battery management system, applied to the aforementioned battery management system, comprising: Obtain the electrical characteristic parameters of the connection points between each screw and the busbar; The electrical characteristic parameters are compared with the corresponding initial reference values ​​to determine the connection status of each connection point, and the degree of abnormality is determined based on the determination result. A graded control strategy is executed based on the degree of abnormality. Specifically, when the degree of abnormality is level 1, dynamic compensation of voltage sampling value is performed; when the degree of abnormality is level 2, a differentiated equalization strategy and / or charging and discharging power limitation are performed; and when the degree of abnormality is level 3, charging and discharging are cut off and a maintenance command is output.

[0010] Furthermore, in the hierarchical control strategy: The dynamic compensation for the voltage sampling value at the first level is: V true =V measured -I sense ×R current V true The actual voltage value after compensation, V measured For the current measured voltage value, I sense R is the current value currently flowing through the connection point. current This is the currently measured contact resistance value; The second-level differentiated balancing strategy includes: reducing the passive balancing discharge current of the battery cell corresponding to the connection point with the second-level abnormality, and / or switching the balancing mode to charging balancing. The third level also outputs maintenance instructions containing the screw position information.

[0011] Further, the step of comparing the electrical characteristic parameters with the corresponding initial reference values, determining the connection status of each connection point, and determining the degree of abnormality based on the determination result includes: After the screws are tightened to a preset torque, the initial reference values ​​for each connection point are established and stored. The initial baseline value was remeasured and updated after maintenance. Calculate the health index HI for each connection point, wherein the health index HI is determined based on at least one of the following parameters: current contact resistance change ΔR, AC impedance change ΔZ, connection point temperature change ΔT, and voltage ripple change. When the health index HI is in different preset ranges, the control strategy of the first level, the second level, or the third level is executed respectively.

[0012] Furthermore, the acquisition of electrical characteristic parameters includes the following methods: When the battery pack has no charging or discharging current and this continues for more than a preset time, a DC detection current is actively injected into the connection point to measure the current contact resistance. When the charger is plugged in but charging has not yet started, an AC detection signal is injected into the connection point to measure the AC impedance; During charging and discharging operation, the voltage ripple signal of the connection point is passively acquired, and the connection status is determined by the ripple phase difference.

[0013] Furthermore, switching the equalization mode to charging equalization includes: During the charging process, the BMS actively controls the charger to supplement the battery cells corresponding to the connection points with an abnormality level of 2 with a preset current that is less than the normal charging current. This ensures that the equalization current avoids the path of the connection point with abnormal contact resistance, thereby reducing the risk of overheating at that connection point.

[0014] Furthermore, the step of obtaining electrical characteristic parameters also includes adaptive detection frequency adjustment: Record the historical rate of change of contact resistance at each of the aforementioned connection points; For connection points where the historical rate of change exceeds the first rate of change threshold, the detection frequency will be increased from the first frequency to the second frequency. For connection points where the historical rate of change is lower than the second rate of change threshold, the detection frequency is reduced from the first frequency to the third frequency, where the third frequency is lower than the first frequency.

[0015] Furthermore, the control methods also include: The step of obtaining electrical characteristic parameters is automatically triggered within a first preset time after charging ends, and the detection result is compared with the detection result before charging after the execution is completed. If the increase in contact resistance after charging compared to the contact resistance before charging exceeds a preset increment threshold, it is determined that the connection point has become thermally loose during charging. Contact resistance detection will be forcibly performed and charging current will be limited before the next charging.

[0016] Furthermore, the control method also includes a cross-validation step: When the contact resistance of a certain connection point increases abnormally, obtain the contact resistance values ​​of at least two other connection points adjacent to that connection point; If the contact resistance values ​​of the adjacent connection points are all within the normal range, the connection point is determined to be an independent loosening fault, and a hierarchical control strategy is executed for the connection point. If the contact resistance value of at least one of the adjacent connection points also increases abnormally, it is determined that there is a regional connection fault, and a higher level of overall control measures than the current fault level are implemented.

[0017] Furthermore, the control method also includes a remaining lifetime prediction step: Obtain the contact resistance value sequence of each connection point at multiple historical time points, perform linear regression on the contact resistance value sequence, and calculate the regression slope; When the regression slope is positive and exceeds the first slope threshold, the remaining time required to reach the anomaly threshold is calculated based on the regression slope. When the remaining time is less than a preset time threshold, a preventative maintenance prompt containing the remaining time is output.

[0018] Beneficial effects: In this application, the threaded holes are located on the busbar rather than on the battery terminals, allowing integrators to directly purchase commercially available finished batteries for assembly without needing to order custom-made terminals with threaded holes from battery manufacturers, thus lowering the procurement threshold and production costs. Furthermore, if the threaded holes on the busbar become stripped or damaged during long-term use, only the busbar needs to be replaced, without scrapping the entire battery cell, significantly reducing maintenance costs and repair difficulty. Screws pass through the through-hole above the BMS circuit board and are screwed into the threaded holes of the busbar, directly fixing the BMS circuit board to the busbar. The screws also serve as voltage sampling contacts, making electrical contact with the busbar. The voltage signal travels directly to the sampling chip via the path of "terminal-busbar-screw-BMS circuit board," without any additional adapters, resulting in low signal transmission loss, strong anti-interference capability, and improved voltage sampling accuracy. In addition, the screws simultaneously perform the dual functions of mechanical fixation and voltage sampling, eliminating the need for traditional voltage sampling harnesses and connectors, reducing the number of parts, and simplifying the assembly process.

[0019] In the control method of this application, by real-time monitoring of the electrical characteristic parameters of the connection point and implementing a hierarchical control strategy, a shift from "passively accepting the consequences of loosening" to "actively identifying and intervening in loosening risks" is achieved, significantly improving system safety. The hierarchical control strategy implements differentiated control measures based on the degree of abnormality—at the first level, dynamic compensation of voltage sampling values ​​is performed to eliminate measurement errors; at the second level, a differentiated balancing strategy and / or charging / discharging power limitation are implemented to avoid overheating at poor contact points; and at the third level, charging / discharging is cut off and a precise positioning maintenance command is output—ensuring neither excessive intervention affecting user experience during minor abnormalities nor insufficient response leading to safety accidents during severe abnormalities. In the second-level differentiated balancing strategy, by reducing the passive balancing discharge current of the battery cell corresponding to the abnormal connection point and / or switching to charging balancing mode, the balancing current avoids the path of the connection point with abnormal contact resistance, fundamentally preventing additional Joule heat at poor contact points, protecting the connection point and battery, and extending the overall lifespan of the system. The maintenance command output at the third level includes specific screw location information and torque requirements, enabling maintenance personnel to quickly locate the fault point without having to check all screws one by one, significantly improving maintenance efficiency. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a battery management system without a BMS circuit board installed according to an embodiment of the invention. Figure 2 This is a schematic diagram of the structure of a battery management system according to an embodiment of the invention; Figure 3 This is a flowchart illustrating a control method for a battery management system according to an embodiment of the invention. Wherein: 1-Single cell; 2-Busbar; 3-Threaded hole; 4-Screw; 5-BMS circuit board.

[0021] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0022] To make the objectives, technical solutions, 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.

[0023] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of features, integers, steps, operations, elements, modules, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, modules, components, and / or groups thereof. It should be understood that when we say an element is “connected” or “coupled” to another element, it can be directly connected or coupled to the other element, or there may be intermediate elements. Furthermore, “connected” or “coupled” as used herein can include wireless connections or wireless coupling. The term “and / or” as used herein includes all or any modules and all combinations of one or more associated listed items.

[0024] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined as herein.

[0025] Reference Figure 1 and Figure 2 This invention provides a battery management system for use in light electric vehicles, comprising: The battery module is composed of multiple individual batteries 1, and a busbar 2 is fixedly connected to the terminal post of each individual battery 1. BMS circuit board 5 integrates a voltage sampling module; The busbar 2 has a threaded hole 3, and the BMS circuit board 5 has a corresponding through hole. The BMS circuit board 5 is positioned above the busbar 2. The screw 4 passes through the through hole and is screwed into the threaded hole 3 to directly fix the BMS circuit board 5 to the busbar 2. The screw 4 also serves as a voltage sampling contact and makes electrical contact with the busbar 2. The voltage sampling module collects the voltage signal of the single battery 1 through the screw 4 and the busbar 2.

[0026] The battery module in this application is composed of multiple individual battery cells 1 connected in series or parallel. Each individual battery cell 1 can be a prismatic lithium iron phosphate cell, a cylindrical cell, or a pouch cell; this application does not limit the specific type. Each individual battery cell 1 has a positive terminal and a negative terminal, with a busbar 2 fixedly connected to the terminal. The busbar 2 is a conductive metal sheet, which can be an aluminum, copper, or nickel busbar. One end of the busbar 2 is fixedly connected to the battery terminal via laser welding or resistance welding, and the other end extends beyond the terminal area to achieve electrical connection with an external circuit. This application provides threaded holes 3 in the extended area of ​​the busbar 2. The threaded holes 3 can be formed by drilling and tapping, and their diameter and pitch are determined according to the specifications of the selected screw 4. Alternatively, the threaded holes can be embedded in the extended area of ​​the busbar 2 in a metal nut that matches the screw 4. For example, when an M4 screw 4 is selected, the nominal diameter of the threaded hole 3 is 4 mm, and the pitch is 0.7 mm.

[0027] BMS circuit board 5 is a printed circuit board assembly that integrates electronic components such as a voltage sampling module, microcontroller, and equalization circuit. Through holes are provided on BMS circuit board 5 corresponding to the threaded holes 3 of each busbar 2. The diameter of the through holes is slightly larger than the outer diameter of the screw 4, allowing the screw 4 to pass through freely. BMS circuit board 5 is positioned above the busbar 2.

[0028] The screw 4 of this application passes through the through hole from above the BMS circuit board 5 and is screwed into the threaded hole 3 of the busbar 2, directly fixing the BMS circuit board 5 to the busbar 2. After the screw 4 is tightened, the lower surface of its head forms a tight mechanical and electrical contact with the sampling pads arranged around the through hole on the BMS circuit board 5. At the same time, the screw shank forms a threaded contact with the inner wall of the threaded hole 3 of the busbar 2. Due to the large contact area of ​​the threaded contact, a reliable electrical contact is formed between the two. Thus, a complete voltage sampling electrical path is formed from the terminal of the single cell 1 to the busbar 2, then through the screw 4 to the sampling pads of the BMS circuit board 5, and finally to the voltage sampling module. The voltage sampling module collects the voltage signal of the corresponding single cell 1 through this electrical path.

[0029] This application allows integrators to directly purchase commercially available batteries for assembly by placing the threaded hole 3 on the busbar 2 instead of the battery terminals, eliminating the need to order terminals with threaded holes 3 from battery manufacturers and lowering the procurement threshold. Furthermore, if the threaded hole 3 on the busbar 2 becomes stripped or damaged during long-term use, only the busbar 2 needs to be replaced, without scrapping the entire battery cell, resulting in low maintenance costs. In addition, the voltage signal reaches the sampling chip directly via the path of "terminal - busbar 2 - screw 4 - BMS circuit board 5," without any additional adapters, resulting in low signal transmission loss and strong anti-interference capability.

[0030] Reference Figure 3This application also provides a control method for a battery management system, applied to the battery management system described above, including: S1: Obtain the electrical characteristic parameters of the connection points between each screw and the busbar; S2: Compare the electrical characteristic parameters with the corresponding initial reference values ​​to determine the connection status of each connection point, and determine the degree of abnormality based on the determination result; S3: Execute a graded control strategy according to the degree of abnormality, wherein when the degree of abnormality is the first level, perform dynamic compensation of voltage sampling value; when the degree of abnormality is the second level, perform differentiated equalization strategy and / or charge and discharge power limitation; when the degree of abnormality is the third level, cut off charging and discharging and output maintenance command.

[0031] The control method of this application is applied to the aforementioned battery management system. This control method is implemented in the microcontroller of the BMS through a software program and is executed cyclically throughout the entire life cycle of the battery pack.

[0032] As described in the steps above, obtain the electrical characteristic parameters of each screw's connection point with the busbar. These electrical characteristic parameters are evaluation indicators used to diagnose the screw connection status under testing conditions, including but not limited to DC contact resistance (R), AC impedance (Z), and feature quantities extracted from the voltage ripple signal. It should be noted that these electrical characteristic parameters are different from the battery terminal voltage signal (V) acquired by the voltage sampling module under normal operating conditions. measuredThe two differ in their acquisition methods and applications. The voltage sampling module continuously collects the terminal voltage of each cell during normal battery charging and discharging, serving as the basic data for the BMS to perform SOC estimation, equalization control, and protection judgment. Electrical characteristic parameters, on the other hand, are diagnostic indicators obtained within a specific detection window by injecting a detection current into the connection point or by performing frequency domain analysis on the voltage signal, used to evaluate the contact state of the screw connection point. The magnitude of contact resistance depends on factors such as contact pressure, contact area, and surface oxidation degree. When the screw loosens, the contact pressure decreases, and the contact resistance increases. In this application, the BMS acquires the electrical characteristic parameters of each screw connection point through a contact resistance detection unit mounted on the BMS circuit board. The contact resistance detection unit is electrically connected to each screw connection point, injects a small detection current into the screw connection point under a preset detection state, and calculates the contact resistance value by measuring the voltage drop across the connection point. The amplitude of the detection current is much smaller than the normal charging and discharging current of the battery and will not affect the normal operation of the battery. The duration of each detection is less than 200ms, and the energy consumption of a single detection is less than 0.5mAh. For example, in one specific implementation, when the battery pack has no charging or discharging current for more than 30 minutes, the BMS automatically enters a low-power detection mode. The contact resistance detection unit sequentially injects a 10mA DC detection current into each connection point, measures the voltage drop across each connection point, and calculates the current contact resistance value of each connection point according to Ohm's law.

[0033] The electrical characteristic parameters are compared with the corresponding initial reference values ​​to determine the connection status of each connection point, and the degree of abnormality is determined based on the judgment results. The initial reference values ​​refer to the electrical characteristic parameter values ​​of each connection point measured under standard environmental conditions after the battery management system is assembled and the screws are initially tightened to the preset torque. These values ​​serve as a reference baseline for subsequent judgments of changes in connection status. The initial reference values ​​are stored in the BMS's storage unit. For the i-th connection point, the change in contact resistance ΔR is calculated. i =R curren_i -R 0_i According to ΔR i The magnitude of ΔR determines the degree of anomalousness at the connection point. Optionally, if ΔR i If it is less than the first threshold, it is judged as a normal state; if ΔR i If ΔR is greater than or equal to the first threshold and less than the second threshold, it is judged as a first-level anomaly; if ΔR i If ΔR is greater than or equal to the second threshold and less than the third threshold, it is judged as a level two anomaly; i If the value is greater than or equal to the third threshold, it is judged as a level three anomaly. The specific value of the above threshold is determined through experimental calibration based on factors such as screw specifications, busbar material, and contact area.

[0034] A tiered control strategy is implemented based on the severity of the anomaly. When the anomaly is at level one, dynamic compensation of the voltage sampling value is performed. This involves real-time correction of the voltage sampling value using the currently measured contact resistance value to eliminate voltage measurement errors caused by increased contact resistance. When the anomaly is at level two, a differentiated balancing strategy and / or charge / discharge power limitation are implemented. The differentiated balancing strategy refers to applying different balancing control strategies to different battery cells based on the severity of the anomaly at each connection point. For example, reducing the balancing current or switching the balancing mode for the battery cell corresponding to the abnormal connection point. Charge / discharge power limitation actively restricts the charging and / or discharging power of the battery pack to reduce the current flowing through the abnormal connection point, thereby reducing the risk of overheating and further loosening at that connection point. When the anomaly is at level three, charging and discharging are interrupted, and a maintenance command is output. For example, the BMS controls the relays or MOSFETs in the charging / discharging circuit to disconnect, and displays a maintenance command containing specific screw location information on the instrument panel.

[0035] This application achieves a shift from "passively accepting the consequences of loosening" to "actively identifying and intervening in loosening risks" by real-time monitoring of the electrical characteristic parameters of the connection points and implementing a hierarchical control strategy, significantly improving system safety. The hierarchical control strategy implements differentiated control measures according to the degree of anomaly, avoiding excessive intervention that affects user experience during minor anomalies and insufficient response that could lead to safety incidents during severe anomalies.

[0036] In one embodiment, the above hierarchical control strategy: The dynamic compensation for the voltage sampling value at the first level is: V true =V measured -I sense ×R current V true The actual voltage value after compensation, V measured For the current measured voltage value, I sense R is the current value currently flowing through the connection point. current This is the currently measured contact resistance value; The second-level differentiated balancing strategy includes: reducing the passive balancing discharge current of the battery cell corresponding to the connection point with the second-level abnormality, and / or switching the balancing mode to charging balancing. The third level also outputs maintenance instructions containing the screw position information.

[0037] In this application, the dynamic compensation for the first-level voltage sampling value is calculated using the following formula: V true =V measured -I sense ×R current Among them, I senseThe value of the current flowing through the connection point is obtained through the current sensor of the BMS; it is positive during charging and negative during discharging; R current This is the currently measured contact resistance value. When the current is positive (charging), I... sense ×R current When the current is positive, the compensated voltage value is less than the measured value; when the current is negative (discharge), the compensated voltage value is greater than the measured value. The compensated voltage value is used for all subsequent BMS functions, including SOC estimation, charge / discharge termination judgment, and equalization control. The compensation operation is performed in real time within each voltage sampling cycle to ensure the accuracy and real-time performance of the voltage value.

[0038] Furthermore, in one embodiment, since the measured value of contact resistance is affected by temperature, and the temperature coefficient of resistance of aluminum is approximately 0.00429 / °C, when the temperature change is large, introducing a temperature correction term can obtain a more accurate compensation result. Specifically, a temperature-resistance coupling compensation formula can be used: V true =V measured -I sense ×R current ×[1+α(T T0)] Where α is the temperature coefficient of resistance of the bus material (0.00429 / °C for aluminum, 0.00393 / °C for copper), T is the current temperature, and T0 is the ambient temperature at the time of the initial reference value measurement. Taking a certain connection point as an example, assume V measured =3.850V, discharge current I sense =-12A, R current =1.8mΩ, temperature T=45°C, T0=25°C, α=0.00429 / °C, then the temperature correction factor is 1+0.00429×(45-25)=1.0858, and the compensation voltage is (-12)×0.0018×1.0858=-0.0235V, V true =3.850-(-0.0235)=3.8735V. If temperature correction is not considered, the compensation value is only (-12)×0.0018=-0.0216V, which is about 0.0019V. In high-precision applications, this difference cannot be ignored.

[0039] In the second-level differentiated balancing strategy, when a connection point is determined to be a second-level anomaly, the BMS identifies the battery cell corresponding to the abnormal connection point and reduces the duty cycle of the balancing MOSFET in that channel to 30% of the normal value, thereby reducing the balancing current from the normal 100mA to approximately 30mA. The purpose of reducing the balancing current is to decrease the current flowing through the abnormal connection point and avoid excessive Joule heating at connection points with high contact resistance. Simultaneously, the BMS switches the balancing mode of that battery cell to charging balancing, that is, actively controlling the charger to supplement the battery cell with a smaller current during charging, so that the balancing current no longer flows through the abnormal screw connection path, thus fundamentally eliminating the possibility of additional heat generation at the abnormal connection point.

[0040] In the third level, the BMS reads the pre-stored connection point location mapping table from the storage unit, obtains the physical location corresponding to the connection point, and generates the maintenance instruction format as follows: "Please use a torque wrench to tighten the Xth screw (located in the Yth bus of [polarity]) to [N] N·m, and then press and hold the reset button."

[0041] In one embodiment, the above-mentioned comparison of the electrical characteristic parameters with the corresponding initial reference values, determination of the connection status of each connection point, and determination of the degree of abnormality based on the determination result includes: After the screws are tightened to a preset torque, the initial reference values ​​for each connection point are established and stored. The initial baseline value was remeasured and updated after maintenance. Calculate the health index HI for each connection point, wherein the health index HI is determined based on at least one of the following parameters: current contact resistance change ΔR, AC impedance change ΔZ, connection point temperature change ΔT, and voltage ripple change. When the health index HI is in different preset ranges, the control strategy of the first level, the second level, or the third level is executed respectively.

[0042] In this application, during the assembly process of the battery management system before it leaves the factory, operators use a calibrated torque wrench to tighten all screws to a preset torque. At room temperature, the BMS injects multi-frequency detection current into each screw connection point, measures and records the DC contact resistance R0 and AC impedance Z0 of each connection point, and writes the data into the EEPROM. Each time the user completes a maintenance operation, pressing the reset button or connecting the maintenance equipment to the BMS causes the BMS to re-execute the measurement process, obtain new reference values, and update the stored data in the EEPROM. Furthermore, the BMS continuously records the changing trend of the contact resistance at each connection point. When the slope of the contact resistance change curve at a certain connection point continues to increase, the BMS can output a warning message before the health index of that connection point reaches an abnormal threshold.

[0043] The Health Index (HI) is a comprehensive indicator used to quantitatively evaluate the health status of screw connections. Its value ranges from 0% to 100%, with a higher HI value indicating a better connection condition. In this application, the calculation of HI comprehensively considers multiple parameters, including changes in contact resistance, AC impedance, temperature, and voltage ripple. In one embodiment, the formula for HI is:

[0044] In another implementation, to more accurately reflect the connectivity status, an S-shaped nonlinear health index model can be used, the calculation formula of which is:

[0045]

[0046] Where j=1,2,3,4 correspond to the four parameters ΔR, ΔZ, ΔT, and ΔV, respectively, and β j The steepness coefficient (β) of the S-curve for each parameter j >0), w j Σw represents the weighting coefficients. j =1. Typical values ​​for each parameter are as follows: Threshold R for contact resistance change ΔR. threshold It is 5.0 mΩ, and the steepness β is 0.0 mΩ. R The weight is 8, and the weight is w. R The threshold value Z for the change in AC impedance ΔZ is 0.45. threshold The Ω is 3.0 mΩ, and the kurtosis is β. Z The threshold value is 6, and the weight w_Z is 0.25; the threshold value for temperature change ΔT is... Tthreshold The temperature is 15°C, and the steepness is β. T The weight is 4, and the weight w T The threshold value V for voltage ripple change ΔV is 0.20. threshold 5mV, steepness β V The weight is 5, and the weight w V It is 0.10.

[0047] Taking ΔR as an example, when ΔR=0, σ R =1 / [1+exp(-8×(0-0.5))]=1 / [1+exp(4)]≈0.018, the parameter contribution value is about 98.2%; when ΔR=R threshold At that time, σ R=1 / [1+exp(-8×0.5)]=1 / [1+exp(-4)]≈0.982, the parameter contribution value is about 1.8%. The advantage of the S-shaped nonlinear model is that when each parameter is within the normal range, the health index changes smoothly and will not produce false alarms due to small fluctuations; when the parameter is close to the abnormal threshold, the sensitivity of the health index is significantly improved, and the risk trend that is about to reach the threshold can be identified earlier. The weight allocation principle is as follows: ΔR is a direct physical quantity reflecting the contact state and has the highest weight; ΔZ is sensitive to surface oxidation and has the second highest weight; ΔT reflects the heating state and provides auxiliary information; ΔV reflects the dynamic contact stability and has the lowest weight. It should be noted that the specific values ​​of the above thresholds, weights, coefficients, etc. are only preferred values ​​for this embodiment. Those skilled in the art can adjust them through a limited number of conventional tests according to the busbar material, screw specifications, and battery capacity.

[0048] When HI ≥ 90%, the connection status is considered normal; when 75% ≤ HI < 90%, it is considered a first-level abnormality; when 50% ≤ HI < 75%, it is considered a second-level abnormality; when HI < 50%, it is considered a third-level abnormality.

[0049] In one embodiment, the above-mentioned method for obtaining electrical characteristic parameters includes the following: When the battery pack has no charging or discharging current and this continues for more than a preset time, a DC detection current is actively injected into the connection point to measure the current contact resistance. When the charger is plugged in but charging has not yet started, an AC detection signal is injected into the connection point to measure the AC impedance; During charging and discharging operation, the voltage ripple signal of the connection point is passively acquired, and the connection status is determined by the ripple phase difference.

[0050] This application provides three methods for obtaining electrical characteristic parameters.

[0051] Method 1 is static DC detection. The BMS continuously monitors the charging and discharging current of the battery pack. When it detects no charging or discharging current for more than 30 minutes, the BMS automatically enters a low-power detection mode. The contact resistance detection unit sequentially injects a 10mA DC detection current into each connection point, measures the voltage drop across each connection point, and calculates the current contact resistance value. The total detection time is less than 200ms, and the daily power consumption is less than 0.5mAh, which has a negligible impact on the vehicle's range.

[0052] Method two involves pre-charging AC detection. When the BMS detects the charger insertion signal but charging has not yet started, it injects a 1kHz, 50mA AC detection signal into each connection point and measures the AC impedance Z_ac at each connection point. AC impedance is highly sensitive to oxide or contamination layers on the contact surface. When oxidation is present on the connection point surface, the AC impedance increases significantly, while the change in DC contact resistance may not be noticeable. Therefore, pre-charging AC detection can identify oxidation or contamination problems on the contact surface at an early stage. In one embodiment, if Z... ac If / Z0>1.5, the message "The charging interface contact surface may be oxidized, cleaning is recommended" will be displayed.

[0053] Method three involves in-operation ripple detection. During vehicle operation, loads such as the motor controller generate current ripple. The BMS passively acquires the voltage ripple signals at each connection point through a voltage sampling module. The acquired signals undergo FFT transformation to extract the ripple amplitude and phase at a 1kHz frequency. When the contact resistance at a connection point increases abnormally, the voltage ripple phase at that point shifts. By comparing the difference between the ripple phase at each connection point and the reference phase, it's possible to help determine if the connection status is abnormal. This method requires no additional signal injection and consumes no battery power.

[0054] The three detection methods cover three different operating conditions: static, before charging, and during operation, realizing full-time connection status monitoring. The three methods complement each other and together constitute a complete connection status detection system.

[0055] In one embodiment, switching the equalization mode to charging equalization includes: During the charging process, the BMS actively controls the charger to supplement the battery cells corresponding to the connection points with an abnormality level of 2 with a preset current that is less than the normal charging current. This ensures that the equalization current avoids the path of the connection point with abnormal contact resistance, thereby reducing the risk of overheating at that connection point.

[0056] In this application, when a connection point is determined to be a Level 2 anomaly, the BMS switches the balancing mode of the corresponding battery cell to charging balancing. During normal charging, the charger charges the entire battery pack in a constant current-constant voltage mode. In charging balancing mode, the BMS sends a command to the charger via the communication interface, requesting the charger to provide additional supplementary charging current to the specific battery cell. Specifically, for the battery cell corresponding to the abnormal connection point, the BMS controls the charger to provide an additional preset small current (e.g., 0.05C, i.e., 5% of the battery's rated capacity) to the battery cell in addition to the normal charging current. This supplementary charging current does not pass through the abnormal screw connection point path, but is directly delivered to the battery cell through the charger's independent balancing channel. In this way, the battery cell receives slightly more charge than other batteries during charging, causing its voltage to gradually approach that of the other batteries. Since the balancing current does not pass through the abnormal screw connection point, no additional Joule heat is generated at this connection point, thereby avoiding further deterioration of the connection point due to overheating. Compared to traditional passive equalization (which consumes energy and generates heat on abnormal connection point paths), the charging equalization method of this application has significant safety advantages when the connection point is abnormal.

[0057] In one embodiment, the above-described step of obtaining electrical characteristic parameters further includes adaptive detection frequency adjustment: Record the historical rate of change of contact resistance at each of the aforementioned connection points; For connection points where the historical rate of change exceeds the first rate of change threshold, the detection frequency will be increased from the first frequency to the second frequency. For connection points where the historical rate of change is lower than the second rate of change threshold, the detection frequency is reduced from the first frequency to the third frequency, where the third frequency is lower than the first frequency.

[0058] In this application, the BMS maintains a contact resistance history table for each connection point, storing the contact resistance values ​​from the most recent N tests and their corresponding timestamps. After each test, the BMS calculates the historical rate of change for each connection point, i.e., it performs a linear fit on the most recent M test values ​​and calculates the slope of the fitted line. The historical rate of change reflects the stability of the contact state at that connection point; the larger the historical rate of change, the more unstable the contact state at that connection point, and the higher the risk of loosening.

[0059] This application employs an adaptive detection frequency adjustment logic. When the historical rate of change of a connection point exceeds a first rate of change threshold, it indicates that the contact condition of that connection point is rapidly deteriorating. The BMS then increases the detection frequency of that connection point from the default first frequency to a second frequency. For example, if the contact resistance of a connection point rapidly increases from 0.28 mΩ to 0.68 mΩ in the past 30 days, with a rate of change of 0.013 mΩ / day, exceeding the first rate of change threshold of 0.01 mΩ / day, the BMS increases its detection frequency from once every 7 days to once a day. When the historical rate of change of a connection point is below a second rate of change threshold, it indicates that the contact condition of that connection point is very stable. The BMS then decreases the detection frequency of that connection point from the default first frequency to a third frequency. For example, if the contact resistance of a connection point only changes from 0.30 mΩ to 0.35 mΩ in 30 days, with a rate of change of 0.0017 mΩ / day, below the second rate of change threshold of 0.005 mΩ / day, the BMS decreases its detection frequency from once every 7 days to once every 30 days.

[0060] The adaptive detection frequency adjustment enables "on-demand detection," which encrypts detection for high-risk connection points and reduces the detection frequency for stable connection points, thereby minimizing detection energy consumption while ensuring security monitoring.

[0061] In one embodiment, the control method further includes: The step of obtaining electrical characteristic parameters is automatically triggered within a first preset time after charging ends, and the detection result is compared with the detection result before charging after the execution is completed. If the increase in contact resistance after charging compared to the contact resistance before charging exceeds a preset increment threshold, it is determined that the connection point has become thermally loose during charging. Contact resistance detection will be forcibly performed and charging current will be limited before the next charging.

[0062] In this application, the BMS performs a contact resistance detection once before each charging begins, and records the contact resistance value R of each connection point before charging. before After charging is complete, the BMS automatically triggers a contact resistance detection within the first preset time (e.g., within 5 minutes) after charging ends, recording the contact resistance value R_after at each connection point. For the i-th connection point, the resistance increment ΔR after charging relative to before charging is calculated. charge,i =R after,i -R before,i If ΔR charge,i If the value exceeds a preset incremental threshold (e.g., 1mΩ), it is determined that the connection point has become thermally loose during the charging process.

[0063] The physical mechanism of thermal loosening lies in the fact that the temperature of the battery and busbar rises during charging, and the coefficients of thermal expansion of the screw, busbar, and BMS circuit board are different (the coefficient of thermal expansion of aluminum is 23 × 10⁻⁶). -6 / °C, stainless steel is 17×10 -6 Temperatures of 0.5°C or higher can cause changes in the preload of the screw, potentially leading to loosening. Conventional static testing methods cannot detect this intermittent loosening related to temperature, while the post-charge testing method of this application is specifically designed to identify this failure mode.

[0064] Upon detecting thermal loosening, the BMS records the event and enforces contact resistance detection before the next charge, while limiting the charging current to 50% of the rated value. For example, if the contact resistance of a connection point is 0.35mΩ before charging, and rises to 1.50mΩ within 5 minutes after charging is completed (an increase of 1.15mΩ exceeding the 1mΩ threshold), the BMS determines it to be thermal loosening, enforces the detection during the next charge, and limits the maximum charging current from 50A to 25A.

[0065] In one embodiment, the control method further includes a cross-validation step: When the contact resistance of a certain connection point increases abnormally, obtain the contact resistance values ​​of at least two other connection points adjacent to that connection point; If the contact resistance values ​​of the adjacent connection points are all within the normal range, the connection point is determined to be an independent loosening fault, and a hierarchical control strategy is executed for the connection point. If the contact resistance value of at least one of the adjacent connection points also increases abnormally, it is determined that there is a regional connection fault, and a higher level of overall control measures than the current fault level are implemented.

[0066] In this application, after completing the contact resistance detection at each connection point, the BMS performs anomaly detection for each connection point. When the contact resistance of a connection point is determined to be abnormally high, the BMS initiates a cross-validation process. The BMS reads the connection point topology information of the battery module from the storage unit, identifies at least two other connection points adjacent to the current connection point, obtains the current contact resistance values ​​of these two adjacent connection points, and compares them with their respective normal ranges. Adjacent connection points are under similar physical environments and vibration conditions, and their contact states have a certain spatial correlation.

[0067] If the contact resistance values ​​of adjacent connection points are all within the normal range, the connection point is determined to be an independent loosening fault, and a hierarchical control strategy for that single point is implemented. If the contact resistance value of at least one of the adjacent connection points is also abnormally high, a regional connection fault is determined, and a higher level of overall control measures than the current fault level are implemented. For example, if the fault level of connection point 5 is Level 1 (ΔR=1.8mΩ), but connection point 6 also has a Level 1 fault (ΔR=2.1mΩ), then a regional connection fault is determined, and the BMS implements Level 2 control measures.

[0068] Cross-validation, by introducing spatial correlation judgment, effectively distinguishes between "individual faults" and "regional faults," avoiding "single-point misjudgment" or "regional missed judgment" caused by local vibration anomalies, and improving the accuracy of fault judgment and the effectiveness of control measures.

[0069] In one embodiment, the control method further includes a remaining lifetime prediction step: Obtain the contact resistance value sequence of each connection point at multiple historical time points, perform linear regression on the contact resistance value sequence, and calculate the regression slope; When the regression slope is positive and exceeds the first slope threshold, the remaining time required to reach the anomaly threshold is calculated based on the regression slope. When the remaining time is less than a preset time threshold, a preventative maintenance prompt containing the remaining time is output.

[0070] In this application, the BMS maintains a historical database for each connection point in the storage unit, recording the timestamp of each detection and the corresponding contact resistance value. After accumulating sufficient historical data, the BMS performs linear regression analysis on the contact resistance value sequence for each connection point. For connection point i, its historical data is {(t1,R1),(t2,R2),…,(t…} n ,R n The regression slope 'a' is calculated using the formula:

[0071] When a > 0 and a exceeds the first slope threshold, it indicates that the contact resistance at the connection point is increasing at a significant rate. The BMS calculates the remaining time required to predict the abnormal threshold. In one embodiment, the remaining time is calculated using the following formula:

[0072] When T remaining When the time is less than the preset time threshold, the BMS outputs a preventative maintenance prompt containing the remaining time.

[0073] In one embodiment, since the degradation rate of contact resistance is not a constant value but varies with temperature and current, this application introduces an acceleration factor to correct the regression slope. The acceleration factor is defined as follows:

[0074] Where α is the temperature coefficient of resistance (0.00429 / °C for aluminum), T_0 is the reference temperature (25°C), k_I is the current acceleration coefficient (obtained through experimental calibration, taken as 0.15 in this embodiment), and I_nom is the rated current (50A in this embodiment). The corrected effective degradation rate a eff and remaining time T remaining Calculated using the following formulas respectively:

[0075]

[0076] The physical meaning of the acceleration factor is that the resistivity of metal increases when the temperature rises, and Joule heating is generated when a large current flows through the contact point, which further aggravates oxidation and stress relaxation. If the operating condition factors are not considered, predicting the remaining time with a constant slope will introduce significant errors.

[0077] For example, historical data from a certain connection point, calculated using linear regression, yields a = 0.0075 mΩ / day. Currently, R... current =1.20mΩ, R threshold =5.0mΩ, temperature T=35°C, average current I=30A. Calculated γ=[1+0.00429×(35-25)]×[1+0.15×(30 / 50)²]=1.043×1.054=1.099, a_eff=0.0075×1.099=0.00824mΩ / day, Tr emaining =(5.0-1.2) / 0.00824≈461 days. If the junction subsequently degrades at an accelerated rate, with the slope increasing to 0.12 mΩ / day, T=45°C, I=40A, then γ=[1+0.00429×(45-25)]×[1+0.15×(40 / 50)²]=1.0858×1.096=1.190, a_eff=0.12×1.190=0.1428 mΩ / day, T remaining =(5.0-3.0) / 0.1428≈14 days, which is less than the preset time threshold of 30 days. The BMS output: "Screw No. 3 is expected to reach the abnormal threshold in 14 days. It is recommended to arrange maintenance in advance."

[0078] In one embodiment, the control method described above further includes a trend early warning step: Record the contact resistance values ​​of each connection point at different time points to generate a contact resistance variation curve; When the slope of the change curve continues to increase and exceeds the preset slope threshold, a maintenance prompt message is output before the health index of the connection point reaches the abnormal threshold.

[0079] In this application, the BMS records the contact resistance values ​​of each connection point on a weekly basis, generating a change curve. After each detection, the slope trend between the three most recent detection values ​​is calculated. If the slope of three consecutive detections is positive and increases with each subsequent value, and the slope of the third detection exceeds a preset slope threshold, the BMS outputs a prompt message.

[0080] For example, the weekly rate of change sequence of a certain connection point is 0.04, 0.06, 0.08 mΩ / week, which continues to increase and the slope of the third week is 0.08 > 0.05 (threshold). The health index of this connection point HI=96% is still within the normal range (HI≥90%), but the BMS outputs according to the slope trend: "The contact resistance of screw No. 5 is increasing rapidly. It is recommended to check the torque within this week."

[0081] Trend early warning can identify rapidly deteriorating trends and issue early warnings before health indices reach abnormal thresholds, achieving risk identification earlier than "threshold judgment," which is of great significance for preventing sudden connection failures.

[0082] In one embodiment, the control method further includes a dynamic power limiting step: When the anomaly level is level two, obtain the current contact resistance value R. current Given an initial reference value R0, calculate the resistance increment ΔR = R current -R0; The current power limiting coefficient is determined based on the correspondence between the resistance increment ΔR and the preset multiple power limiting levels. The power limiting factor decreases in a stepwise manner as the resistance increment ΔR increases, and the power limiting factor remains unchanged within a single charge-discharge cycle, and is re-determined based on the new ΔR after the next detection.

[0083] In this application, when a connection point is determined to be a Level 2 anomaly, the BMS activates the dynamic power limiting function. The BMS's storage unit has multiple preset power limiting levels and their corresponding ΔR ranges. The power limiting coefficient λ decreases in a stepwise manner as ΔR increases—the larger ΔR is, the stricter the power limiting. The rules for λ are as follows: when ΔR < 2.0mΩ, λ = 1.00; when 2.0mΩ ≤ ΔR < 3.0mΩ, λ = 0.85; when 3.0mΩ ≤ ΔR < 4.0mΩ, λ = 0.70; when 4.0mΩ ≤ ΔR < 5.0mΩ, λ = 0.55; when ΔR ≥ 5.0mΩ, λ = 0.40.

[0084] The power limiting factor λ remains constant throughout a single charge-discharge cycle. For example, if the power limiting factor is set to 0.70 at the start of a charging cycle, it remains constant at 0.70 throughout the entire charging process. It is not frequently adjusted due to minor changes in ΔR during charging, thus avoiding the adverse effects of frequent power fluctuations on the charger and battery. After the next detection (before the start of the next charge-discharge cycle), the BMS re-determines the power limiting factor λ based on the new ΔR value.

[0085] For example, the initial reference value of a connection point is R_0 = 0.30mΩ, and the current contact resistance is R current =3.50mΩ, ΔR=3.20mΩ. Since 3.0mΩ≤ΔR<4.0mΩ, the corresponding power limiting factor is λ=0.70. The BMS limits the charging current to 70% of the rated value, i.e., 50A×0.70=35A, which remains unchanged within this charge-discharge cycle. If ΔR rises to 4.3mΩ in the next cycle, then λ drops to 0.55, and the charging current is limited to 50A×0.55=27.5A. If ΔR drops to 1.5mΩ (possibly due to user maintenance), then λ returns to 1.00.

[0086] Dynamic power limiting enables fine-tuning of the power limiting coefficient as the contact resistance deteriorates; the larger the resistance increment, the stricter the limitation. The "cycle-lock" mechanism ensures the stability of the charging and discharging process.

[0087] In summary, the battery management system and control method provided in this application achieve a high degree of structural integration by directly fixing the BMS circuit board to the busbar with screws and using the screws as voltage sampling contacts. This eliminates the need for traditional voltage sampling harnesses and connectors, reduces the number of components, and simplifies the assembly process. Furthermore, through the synergistic effect of multiple control methods such as contact resistance detection, hierarchical control, adaptive detection frequency adjustment, cross-validation, and remaining life prediction, comprehensive monitoring and proactive management of the screw connection status are achieved. Compared with existing technologies, this application achieves multiple technical benefits, including structural simplification and cost reduction, improved compatibility and maintainability, guaranteed sampling accuracy, proactive safety management, predictive maintenance, and refined control.

[0088] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A battery management system for use in light electric vehicles, characterized in that, include: A battery module is composed of multiple individual batteries, and a busbar is fixedly connected to the terminal of each individual battery. The BMS circuit board integrates a voltage sampling module; The busbar has a threaded hole, and the BMS circuit board has a corresponding through hole. The BMS circuit board is positioned above the busbar. A screw passes through the through hole and is screwed into the threaded hole to directly fix the BMS circuit board to the busbar. The screw also serves as a voltage sampling contact and makes electrical contact with the busbar. The voltage sampling module collects the voltage signal of the individual battery through the screw and the busbar.

2. A control method for a battery management system, applied to the battery management system as described in claim 1, characterized in that, include: Obtain the electrical characteristic parameters of the connection points between each screw and the busbar; The electrical characteristic parameters are compared with the corresponding initial reference values ​​to determine the connection status of each connection point, and the degree of abnormality is determined based on the determination result. A graded control strategy is executed based on the degree of abnormality. Specifically, when the degree of abnormality is level 1, dynamic compensation of voltage sampling value is performed; when the degree of abnormality is level 2, a differentiated equalization strategy and / or charging and discharging power limitation are performed; and when the degree of abnormality is level 3, charging and discharging are cut off and a maintenance command is output.

3. The control method according to claim 2, characterized in that, In the hierarchical control strategy: The dynamic compensation for the voltage sampling value at the first level is: V true = V measured - I sense × R current V true The actual voltage value after compensation, V measured For the current measured voltage value, I sense R is the current value currently flowing through the connection point. current This is the currently measured contact resistance value; The second-level differentiated balancing strategy includes: reducing the passive balancing discharge current of the battery cell corresponding to the connection point with the second-level abnormality, and / or switching the balancing mode to charging balancing. The third level also outputs maintenance instructions containing the screw position information.

4. The control method according to claim 2, characterized in that, The step of comparing the electrical characteristic parameters with the corresponding initial reference values, determining the connection status of each connection point, and determining the degree of abnormality based on the determination result includes: After the screws are tightened to a preset torque, the initial reference values ​​for each connection point are established and stored. The initial baseline value was remeasured and updated after maintenance. Calculate the health index HI for each connection point, wherein the health index HI is determined based on at least one of the following parameters: current contact resistance change ΔR, AC impedance change ΔZ, connection point temperature change ΔT, and voltage ripple change. When the health index HI is in different preset ranges, the control strategy of the first level, the second level, or the third level is executed respectively.

5. The control method according to claim 2, characterized in that, The electrical characteristic parameters are obtained in the following ways: When the battery pack has no charging or discharging current and this continues for more than a preset time, a DC detection current is actively injected into the connection point to measure the current contact resistance. When the charger is plugged in but charging has not yet started, an AC detection signal is injected into the connection point to measure the AC impedance; During charging and discharging operation, the voltage ripple signal of the connection point is passively acquired, and the connection status is determined by the ripple phase difference.

6. The control method according to claim 3, characterized in that, The step of switching the equalization mode to charging equalization includes: During the charging process, the BMS actively controls the charger to supplement the battery cells corresponding to the connection points with an abnormality level of 2 with a preset current that is less than the normal charging current. This ensures that the equalization current avoids the path of the connection point with abnormal contact resistance, thereby reducing the risk of overheating at that connection point.

7. The control method according to claim 2, characterized in that, The step of obtaining electrical characteristic parameters also includes adaptive detection frequency adjustment: Record the historical rate of change of contact resistance at each of the aforementioned connection points; For connection points where the historical rate of change exceeds the first rate of change threshold, the detection frequency will be increased from the first frequency to the second frequency. For connection points where the historical rate of change is lower than the second rate of change threshold, the detection frequency is reduced from the first frequency to the third frequency, where the third frequency is lower than the first frequency.

8. The control method according to claim 2, characterized in that, The method further includes: The step of obtaining electrical characteristic parameters is automatically triggered within a first preset time after charging ends, and the detection result is compared with the detection result before charging after the execution is completed. If the increase in contact resistance after charging compared to the contact resistance before charging exceeds a preset increment threshold, it is determined that the connection point has become thermally loose during charging. Contact resistance detection will be forcibly performed and charging current will be limited before the next charging.

9. The control method according to claim 2, characterized in that, It also includes a cross-validation step: When the contact resistance of a certain connection point increases abnormally, obtain the contact resistance values ​​of at least two other connection points adjacent to that connection point; If the contact resistance values ​​of the adjacent connection points are all within the normal range, the connection point is determined to be an independent loosening fault, and a hierarchical control strategy is executed for the connection point. If the contact resistance value of at least one of the adjacent connection points also increases abnormally, it is determined that there is a regional connection fault, and a higher level of overall control measures than the current fault level are implemented.

10. The control method according to claim 2, characterized in that, It also includes the remaining lifetime prediction step: Obtain the contact resistance value sequence of each connection point at multiple historical time points, perform linear regression on the contact resistance value sequence, and calculate the regression slope; When the regression slope is positive and exceeds the first slope threshold, the remaining time required to reach the anomaly threshold is calculated based on the regression slope. When the remaining time is less than a preset time threshold, a preventative maintenance prompt containing the remaining time is output.

Images