Cell screening and grouping method and automatic equalization circuit thereof

Abstract

The invention relates to the technical field of battery module assembly, and discloses a battery cell screening and matching method and an automatic equalization circuit thereof, and the method comprises the steps: S1, primary screening of battery cells: forming a first echelon battery cell group; s2, secondary screening of the battery cells: carrying out grading screening on the capacity of the first echelon battery cell group to form a second echelon battery cell group; s3, battery cell matching: matching the battery cells in the capacity gear battery cell group according to module series-parallel requirements to form a third echelon battery cell group; and S4, balancing and assembling the battery cells: automatically balancing and assembling the battery cells in the third echelon battery cell group through an automatic balancing circuit. Through the method of matching and balancing the cells after two times of screening, the consistency of the discharge capacity of the cell module can be improved, the probability of module reworking and disassembling is effectively reduced, the rejection rate of the cell module with substandard capacity is reduced, the working time cost is reduced, the production efficiency is improved, and meanwhile, the complaint of a customer that the capacity is substandard after the cell module is used for a period of time can be reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery module assembly, and particularly relates to a battery cell screening and grouping method and an automatic equalization circuit thereof. BACKGROUND

[0002] In the field of power battery module assembly, the parameter consistency of battery cells is a core prerequisite for determining the performance and reliability of the module, so the industry generally uses a battery cell screening system to pre-detect single battery cells to ensure the quality of module assembly. At present, the core screening dimensions of the traditional battery cell screening system are concentrated on three static parameters of the battery cell, namely, voltage, capacity and K value (capacity attenuation coefficient). The voltage screening is used to exclude battery cells with abnormal open circuit voltage and internal micro-short circuit risk; the capacity screening selects battery cells with a rated capacity deviation within a preset threshold through charge and discharge cycle test; and the K value screening evaluates the capacity attenuation rate of the battery cell in the cycle process and excludes poor quality battery cells with too fast attenuation. However, although the battery cells screened by the traditional screening method meet the parameter consistency requirement in the initial state, the performance difference between the battery cells gradually increases as the storage time prolongs or the charge and discharge cycle number increases after the module assembly is completed. In the charging link, some battery cells with small initial capacity or fast capacity attenuation rate will enter the end of the charging terminal stage in advance when the overall module does not reach the rated charging capacity, and the terminal voltage of the battery cell rapidly rises to the single battery cell overvoltage protection threshold, triggering the module charging protection mechanism, which forces the entire module to stop charging, affecting the charging efficiency and causing the actual charging capacity of the module to be lower than the design value. In the discharging link, due to the cumulative influence of the capacity difference between the battery cells, the capacity bottleneck battery cell will reach the under-voltage protection threshold first in the overall module discharging process, causing the module discharging interruption, resulting in the actual discharging capacity of the module not meeting the requirements, and failing to meet the endurance or power supply requirements of the downstream equipment. The above problems directly lead to the need for secondary detection after the module assembly, and a large number of modules with abnormal charge and discharge protection need to be reworked and disassembled, and the unqualified battery cells need to be replaced, which not only increases the labor cost and battery cell loss, but also prolongs the production cycle. Moreover, some problem modules that are not detected flow into the market, which will cause customer complaints due to fast capacity attenuation, charge and discharge interruption and other faults, seriously affecting the brand reputation of the enterprise, and even increasing the safety hazards such as thermal runaway due to the long-term overvoltage or under-voltage working condition of the battery cell. SUMMARY

[0003] In order to solve the problems of the prior art, the application provides a battery cell screening and grouping method and an automatic equalization circuit thereof. The method of grouping and equalization assembly after twice screening of the battery cell can improve the discharge capacity consistency of the battery cell module, effectively reduce the probability of module reworking and disassembly, reduce the scrap rate of the battery cell module with substandard capacity, reduce the labor cost, improve the production efficiency, and reduce customer complaints due to substandard capacity after a period of use.

[0004] The technical effects to be achieved in this application are realized through the following aspects: In a first aspect, this application provides a method for screening and grouping battery cells, comprising the following steps: S1, Initial screening of battery cells: The battery cell voltage and internal resistance are measured using a battery internal resistance tester. Then, the cells are sorted according to the set voltage, internal resistance, capacity, and K value range using OCV software to form the first-tier battery cell group. S2, Secondary Cell Screening: The capacity of the first tier of cell groups is sorted and screened to form a second tier of cell groups. The upper limit of the capacity of the second tier of cell groups is set to... The lower limit of the capacity of the second-tier cell group is set as follows: The second tier of battery cell groups includes multiple capacity-level battery cell subgroups, each of which corresponds to a capacity range. S3, Cell grouping: The cells in the cell subgroups of the capacity level are grouped according to the module series and parallel requirements to form the third echelon cell group; S4, Cell equalization assembly: The cells in the third echelon of cell groups are automatically equalized and assembled using an automatic equalization circuit.

[0005] In some implementations, the capacity difference of the second-tier cell group It has a relational expression: .

[0006] In some implementations, in S2, the second tier of battery cells includes N capacity-level battery cell subgroups; wherein the N capacity-level battery cell subgroups are respectively a first capacity-level battery cell group, a second capacity-level battery cell group, and an Nth capacity-level battery cell group.

[0007] In some implementations, the capacity range of the first capacity level cell sub-group is: : The capacity range of the second capacity level cell group is ; The capacity range of the Nth capacity level battery cell group is: .

[0008] In some implementations, the second tier of battery cells includes four capacity-level battery cell subgroups; wherein the four capacity-level battery cell subgroups are respectively a first capacity-level battery cell subgroup a, a second capacity-level battery cell subgroup b, a third capacity-level battery cell subgroup c, and a fourth capacity-level battery cell subgroup d; The first capacity level battery cell group has a number of cells a, the second capacity level battery cell group has a number of cells b, the third capacity level battery cell group has a number of cells c, and the fourth capacity level battery cell group has a number of cells d. In S3, a T-series-L-parallel structure is used for module grouping, where T is the total number of series-connected cells and L is the total number of parallel-connected branches of cells.

[0009] In some implementations, when T L At that time, the module grouping has the following relationship: X1 + X2 + +X T Among them, X1 and X2 X T For battery cells, X1+X2+ +X T There are T series-connected battery cells; The capacity level of the battery cell meets any of the following criteria: The X1, X2 X T Either cell a or cell b; or The X1, X2 X T Either cell b or cell c; or The X1, X2 X T These are either cell c or cell d.

[0010] In some implementations, when T L And when L is an even number, the module grouping has the following relationship:

[0011] And relation two: ; Among them, Y1 and Y2 Y n Cells a and d are connected in parallel, respectively; Z1 and Z2 Z n Cells b and c are connected in parallel, respectively; for indivual and indivual Parallel connection.

[0012] In some implementations, when T L And when L is an odd number, the module grouping has the following relationship:

[0013] And relation two: ; Among them, X1 and X2 X n Each of the following is a battery cell: cell a, cell b, cell c, or cell d; Y1 and Y2 Y n Cells a and d are connected in parallel, respectively; Z1 and Z2 Z n Cells b and c are connected in parallel, respectively; for indivual as well as indivual Parallel connection.

[0014] Secondly, this application provides an automatic balancing circuit applicable to the cell balancing assembly step of the above-mentioned cell screening and grouping method; The automatic balancing circuit includes multiple battery polarity monitoring and switching protection branch modules and a common power supply module. The multiple battery polarity monitoring and switching protection branch modules are connected in parallel, and the battery polarity monitoring and switching protection branch modules are connected to the common power supply module. The common power supply module is used to provide a unified power supply for the battery polarity monitoring and switching protection branch modules.

[0015] In some implementations, the battery polarity monitoring and switching protection branch module includes a battery unit, an optocoupler isolation unit, a relay polarity switching unit, an overcurrent protection unit, and a battery polarity indicator unit; The output terminal of the battery unit is connected to the input terminal of the optocoupler isolation unit; the output terminal of the optocoupler isolation unit is connected to the relay polarity switching unit; the battery polarity indicator unit is connected between the relay polarity switching unit and the common power supply module; and the overcurrent protection unit is connected between the relay polarity switching unit and the overcurrent protection units in other battery polarity monitoring and switching protection branch modules.

[0016] In summary, this application has at least the following advantages: The cell screening and grouping method provided in this application, by conducting initial and secondary screening of cells, and then grouping, balancing and assembling cells of the same capacity range after screening, effectively improves the discharge capacity consistency of cell modules, reduces the probability of modules needing rework and disassembly due to abnormal charging and discharging protection, reduces the scrap rate of cell modules with substandard capacity, reduces labor costs caused by rework, and thus improves production efficiency. At the same time, it can reduce customer complaints about substandard capacity after a period of use. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the cell selection and grouping method in Embodiment 1 of this application.

[0018] Figure 2 This is a schematic diagram of the automatic equalization circuit in Embodiment 3 of this application.

[0019] Marked in the image: 1. Battery polarity monitoring and switching protection branch module; 11. Battery unit; 12. Optocoupler isolation unit; 13. Overcurrent protection unit; 14. Battery polarity indicator unit; 15. Relay polarity switching unit; 2. Common power supply module. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. The described embodiments are only some embodiments of this application, not all embodiments.

[0021] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0022] Example 1: Please see the appendix Figure 1 This application discloses a method for screening and grouping battery cells, comprising the following steps: S1, Initial screening of battery cells: The battery cell voltage and internal resistance are measured using a battery internal resistance tester. Then, the cells are sorted according to the set voltage, internal resistance, capacity, and K value range using OCV software to form the first-tier battery cell group. S2, Secondary Cell Screening: The capacity of the first-tier cell groups is further categorized to form a second-tier cell group. The upper limit of the capacity of the second-tier cell group is set to... The lower limit of the capacity of the second-tier battery cell group is set at The second-tier cell group includes multiple capacity-level cell subgroups, each corresponding to a capacity range; S3, Cell grouping: The cells in the cell subgroups of the capacity level are grouped according to the module series and parallel requirements to form the third echelon cell group; S4, Cell equalization assembly: The cells in the third echelon of cell groups are automatically equalized and assembled using an automatic equalization circuit.

[0023] In this embodiment, the cell screening and grouping method firstly involves obtaining the cell voltage and internal resistance using a battery internal resistance tester in S1. Then, using OCV software, the cells are sorted within a set range to form a first-tier cell group, initially eliminating cells with abnormal parameters and reducing the fundamental risk of module capacity being too low or too high from the source. Secondly, in S2, the cells in the first-tier cell group are categorized by capacity, based on the upper capacity limit. Capacity lower limit To further reduce the capacity differences among cells within the same group, multiple capacity-level cell subgroups are defined, laying a consistent foundation for subsequent grouping and balancing. Then, in S3, the cells in the capacity-level cell subgroups are grouped according to module series-parallel requirements to form a third-tier cell group. Finally, in S4, an automatic balancing circuit balances the cells in the third-tier cell group. Utilizing a self-balancing logic that charges low-voltage cells with high-voltage cells, coupled with a PTC overcurrent disconnect and cooling protection mechanism, the cell voltage is repeatedly calibrated until it becomes consistent. Finally, the balanced cells are assembled.

[0024] The above settings not only reduce hardware complexity due to the simplified circuit design, but also significantly improve the discharge capacity consistency of the third-tier cell group, reduce the probability of modules needing rework and disassembly due to abnormal charging and discharging protection, reduce the scrap rate of cells in the third-tier cell group that do not meet the capacity standards, reduce labor costs caused by rework, thereby improving production efficiency, and at the same time, reduce customer complaints about the capacity not meeting the standards after a period of use.

[0025] In some embodiments, the capacity difference of the second-tier cell group It has a relational expression: .

[0026] By setting the above relationships, a clear boundary can be defined for the capacity of the second-tier cells, further limiting the qualified cells selected in the initial screening in step S1 to the upper limit of capacity. With lower capacity limit Within this range, the initial capacity difference between cells in the second-tier cell group is directly reduced, avoiding the increased processing difficulty caused by excessively large capacity ranges. Simultaneously, based on this total capacity difference, the second-tier cell group can be further divided into multiple capacity-level cell subgroups, each corresponding to a smaller capacity range. This further compresses the capacity difference between cells within a subgroup, resulting in shorter balancing time and lower balancing energy consumption for cells with similar capacities, and faster attainment of voltage consistency, reducing the load on the balancing circuit.

[0027] In the subsequent grouping process in step S3 and the cell equalization assembly process in step S4, since the capacity range of the cells has been standardized by limiting the capacity difference ∆C, the initial capacity deviation of the cells used in the grouping is small. Combined with the voltage consistency after equalization, it can effectively avoid the situation where low-capacity cells drag down the overall discharge capacity in the module. This reduces the risk of low module capacity and also reduces the waste of high-capacity cells that cannot fully release their capacity due to mixing with low-capacity cells, thereby improving the overall discharge capacity utilization rate of the module.

[0028] Furthermore, the clear definition of the capacity difference ∆C makes capacity grading and screening more standardized, reduces grading errors, and ensures the efficient advancement of subsequent processes. Ultimately, it helps to reduce the scrap rate of modules that do not meet the capacity standards, improves production efficiency, and reduces the problem of uneven performance degradation caused by capacity differences during user use, thereby reducing the risk of complaints.

[0029] In some embodiments, in S2, the second-tier battery cell group includes N capacity-level battery cell subgroups; wherein, the N capacity-level battery cell subgroups are respectively a first capacity-level battery cell group, a second capacity-level battery cell group, and an Nth capacity-level battery cell group.

[0030] By dividing the cells into the above categories, the total capacity range of the second-tier cell group is refined into N smaller independent capacity ranges. This significantly reduces the capacity difference between cells within each subgroup, thereby reducing the initial capacity deviation of cells within the same subgroup from the source. Since the cell capacities within the same subgroup are similar, the balancing circuit can achieve voltage consistency without long-term and large-scale adjustments. This not only effectively shortens the balancing time and reduces balancing energy consumption, but also reduces the load loss of the balancing circuit, extends the service life of the equipment, and ensures the quality of cell matching.

[0031] In some embodiments, the capacity range of the first capacity level cell group is: The capacity range of the second capacity level battery cell pack is: The capacity range of the Nth capacity level battery cell group is: .

[0032] Specifically, the second-tier battery cell group includes four capacity-level battery cell groups; these four capacity-level battery cell groups are the first capacity-level battery cell group, the second capacity-level battery cell group, the third capacity-level battery cell group, and the fourth capacity-level battery cell group; preferably, the capacity range of the first capacity-level battery cell group is 800mAh-900mAh; the capacity range of the second capacity-level battery cell group is 900mAh-1000mAh; the capacity range of the third capacity-level battery cell group is 1000mAh-1100mAh; and the capacity range of the fourth capacity-level battery cell group is 1100mAh-1200mAh.

[0033] The first capacity level battery cell group has several cells 'a', the second capacity level battery cell group has several cells 'b', the third capacity level battery cell group has several cells 'c', and the fourth capacity level battery cell group has several cells 'd'. In S3, a T-series-L-parallel structure is used for module grouping, where T is the total number of series-connected cells and L is the total number of parallel-connected branches. Specifically, the capacity of cell 'a' is any value between 800 mAh and 900 mAh; the capacity of cell 'b' is any value between 900 mAh and 1000 mAh; the capacity of cell 'c' is any value between 1000 mAh and 1100 mAh; and the capacity of cell 'd' is any value between 1100 mAh and 1200 mAh.

[0034] By dividing the total capacity difference ∆C of the second-tier cell group into four small capacity intervals of 100mAh, cell a, cell b, cell c, and cell d are each limited to a very small capacity range. This significantly reduces the initial capacity difference of cells in the capacity-level cell subgroups, enabling the equalization circuit to quickly achieve voltage consistency without significant adjustments, effectively shortening the equalization time.

[0035] After entering the S3 grouping stage, the T-series L-parallel structure and the capacity-level cell subgroups form an efficient match: parallel branches use cells from the same subgroup. Because the cells in the same subgroup have highly consistent capacity, the "weakest link" effect—where a low-capacity cell in a single branch drags down the entire parallel unit—is avoided, ensuring that the capacity of each parallel branch is stable and meets the standard. For example, 4 parallel cells can achieve a stable capacity of 3200mAh-3600mAh. In the series stage, each series unit is composed of parallel branches with consistent capacity, and the voltage difference between the cells is small after balancing, making the total voltage output of the entire module more stable. This reduces the frequent opening and closing of the overcurrent PTC protection action, extends the life of the protection components, and avoids the extra energy consumption of repeated charging adjustments.

[0036] In addition, the four clearly defined capacity range subgroups have extremely strong adaptability and can accurately select the appropriate cell based on the capacity requirements of different modules. That is, cells a are used for modules with low capacity requirements, and cells d are used for modules with high capacity requirements. There is no need to select cells across ranges, which greatly improves the matching efficiency between cells and modules and reduces selection errors.

[0037] By classifying and grouping the battery cells according to their capacity, the discharge capacity consistency and output stability of the battery cell modules are significantly improved. This also reduces the scrap rate of the modules due to capacity deviation, reduces production losses, improves the user experience, achieves more uniform capacity decay of the modules, and effectively reduces the risk of complaints caused by substandard capacity after a period of use.

[0038] In some embodiments, when T L At that time, the module grouping has the following relationship: X1 + X2 + +X T Among them, X1 and X2 X T For battery cells, X1+X2+ +X T The quantity is T cells connected in series; The capacity level of the battery cell meets any of the following criteria: X1, X2 X T Each of the following refers to either cell a or cell b; or X1, X2. X T These are either cell b or cell c; or X1, X2. X T These are either cell c or cell d.

[0039] Specifically, in a 2-series-1-parallel structure, the following modules can be configured: cell a + cell b, cell b + cell c, and cell c + cell d.

[0040] By adopting the above settings and using the selection rules for adjacent battery levels, the capacity difference of series-connected cells is strictly controlled within 100mAh. This completely avoids the "barrel effect" that may occur when low-capacity cells are depleted first, leaving high-capacity cells with unreleased capacity. This ensures that the total capacity of the series-connected module is close to the sum of the capacities of each cell. Furthermore, since the T-series-1-parallel structure has no parallel branch buffer, the parameter consistency of the series-connected cells directly determines the stability of the module. After the cell classification in step S2 and the grouping in step S3, adjacent battery levels not only have similar capacities but also smaller differences in voltage and internal resistance. The circuit current is more uniform when connected in series, which avoids the protection action of the PTC frequently opening or closing due to excessively high or low voltage of a single cell. This reduces the wear and tear on protection components and makes the total voltage output of the module more stable, improving the reliability of power supply.

[0041] Example 2: The difference between this embodiment and Embodiment 1 is that in this embodiment, when T... L And when L is even, the module grouping follows the relationship: ;as well as Relationship 2: ; Among them, Y1 and Y2 Y n Cells a and d are connected in parallel; Z1 and Z2 are respectively. Z n Cells b and c are connected in parallel, respectively. for indivual and indivual Parallel connection.

[0042] Specifically, in a 2-series 2-parallel structure, the following modules can be configured: cell a*cell d+cell a*cell d, cell b*cell c+cell b*cell c, and cell a*cell d+cell b*cell c.

[0043] In this embodiment, the relationship in each parallel unit can be fixed using equation two. quantity and quantity The sum of them is This achieves symmetry and standardization of the parallel unit structure, avoids differences in current carrying capacity caused by imbalance in the number of parallel units, ensures uniform circuit current when each parallel unit is connected in series, reduces the risk of frequent PTC disconnection triggered by unit overload, and extends the life of protection components.

[0044] In addition, by adjusting and The selection of components allows for the formation of tiered parallel unit capacities, which, after being combined in T-series configurations, can meet diverse module capacity requirements without requiring additional adjustments to the tiering rules; simultaneously, standardized... The proportioning reduces the error in the grouping operation and improves the efficiency of mass production. This proportioning design can flexibly adapt to different capacity requirements and can make full use of cells of different grades (a, b, c, and d), reducing the material waste of cells of certain grades.

[0045] The modules assembled with the above structure not only improve discharge stability and capacity consistency due to the consistent capacity of parallel units and uniform series current, but also reduce production costs and scrap rate due to flexible adaptation and high material utilization. At the same time, it improves the user experience caused by uneven capacity decay and reduces the risk of complaints.

[0046] In some embodiments, when T L And when L is an odd number, the module grouping follows the relationship:

[0047] And relation two: ; Among them, X1 and X2 X n Each of the following is a battery cell: cell a, cell b, cell c, or cell d; Y1, Y2 Y n Cells a and d are connected in parallel; Z1 and Z2 are respectively. Z n Cells b and c are connected in parallel, respectively. for indivual as well as indivual Parallel connection.

[0048] Specifically, the following modules can be configured in a 2-series 3-parallel structure: aad+aad, abc+abc, aad+abc, bad+bad, bbc+bbc, bad+bbc, cad+cad, cbc+cbc, cad+cbc, dad+dad, dbc+dbc, dad+dbc.

[0049] Through the above Together they form a regular structure of 3 parallel units, which not only solves the problem of unevenly distributing the number of parallel units when L is odd, but also, through Y... n Z n For adjacent gears, With Y n Z n The limitation of the same cell ad range controls the maximum capacity difference of cells in the 3 parallel units to within 300mAh, which is much smaller than the difference between multiple mixed-grade cells. Combined with the S3, the consistency of cell voltage and internal resistance in the unit is greatly improved, avoiding the barrel effect of low-capacity cells dragging down the entire parallel unit, and ensuring that the capacity of the 3 parallel units is fully released.

[0050] Secondly, in the 2-string structure, whether it is series connection of similar units, such as aad+aad, or series connection of cross-type units, such as aad+abc, because a single 3-parallel unit already has high consistency, the capacity and voltage difference of the two units after series connection is minimal, the circuit current distribution is uniform, which can reduce the protection action of frequent disconnection or closing of overcurrent PTC, reduce the loss of protection components, and at the same time avoid local overheating, making the total voltage output of the module more stable and improving the reliability of power supply.

[0051] This application adapts to diverse end-product needs without requiring adjustments to cell grading, effectively enhancing module design flexibility. The standardized structure and clearly defined cell grading limits allow for a fixed-template assembly process, reducing manual material selection errors and improving batch production efficiency. It also effectively utilizes inventory across cell grades A, B, C, and D, avoiding material waste caused by overstocking of cells in a single grade. Furthermore, this assembly structure ensures efficient module discharge capacity utilization and output stability, balancing production efficiency with product compatibility, effectively reducing the scrap rate of modules with substandard capacity.

[0052] Example 3: This embodiment is based on the above embodiment; please refer to [link / reference]. Figure 2An automatic balancing circuit is provided, which is applicable to the cell balancing assembly step of the above-mentioned cell screening and grouping method. The automatic balancing circuit includes multiple battery polarity monitoring and switching protection branch modules 1 and a common power supply module. The multiple battery polarity monitoring and switching protection branch modules 1 are connected in parallel, and the battery polarity monitoring and switching protection branch modules 1 are connected to the common power supply module. The common power supply module is used to provide a unified power supply for the battery polarity monitoring and switching protection branch modules 1.

[0053] The battery polarity monitoring and switching protection branch module 1 includes a battery unit 11, an optocoupler isolation unit 12, a relay polarity switching unit 15, an overcurrent protection unit 13, and a battery polarity indicator unit 14. The output terminal of the battery unit 11 is connected to the input terminal of the optocoupler isolation unit 12. The output terminal of the optocoupler isolation unit 12 is connected to the relay polarity switching unit 15. The battery polarity indicator unit 14 is connected between the relay polarity switching unit 15 and the common power supply module. The overcurrent protection unit 13 is connected between the relay polarity switching unit 15 and the overcurrent protection units in the other battery polarity monitoring and switching protection branch modules. The optocoupler isolation unit 12 has the function of monitoring battery polarity and controlling the operation of the relay polarity switching unit 15.

[0054] Specifically, battery unit 11 includes a battery cell. Optocoupler isolation unit 12 includes a current-limiting resistor R11 and an optocoupler U1; the output signal of battery unit 11 is current-limited by the current-limiting resistor R11 and then connected to the positive terminal of the light-emitting diode in optocoupler U1, forming a circuit with the negative terminal of the light-emitting diode; the phototransistor side of optocoupler U1 is connected to battery polarity indicator unit 14. Optocoupler isolation unit 12 achieves electrical isolation through electro-optical-electro-electrical conversion, cutting off the direct electrical connection between the battery power supply side and the control side, suppressing interference and ensuring the safety of the control circuit.

[0055] The relay polarity switching unit includes a current-limiting resistor R12 and a relay K1. The current-limiting resistor R12 is connected between the optocoupler isolation unit 12 and the control terminal of the relay K1.

[0056] The overcurrent protection unit 13 includes a PTC resettable fuse F1.

[0057] The battery polarity indicator unit 14 includes a light-emitting diode (LED) 1. The control terminal of a relay K1 is connected to the LED 1. The relay K1 can receive signals from the optocoupler and drive the LED 1, controlling its illumination or deactivation. This unit converts the battery polarity state transmitted by the optocoupler into a direct light indication from the LED 1, facilitating quick determination of the branch's operating status. In the automatic balancing circuit of this embodiment, the battery cell is balanced in parallel with other battery cells through the normally closed terminal of the relay K1 and the PTC resettable fuse F1. If the battery cell polarity is reversed, the PTC resettable fuse F1 temperature switch opens, the optocoupler U1 operates, driving the relay K1 to reverse the polarity. After the temperature switch F1 cools down, it closes, and the normally closed terminal of the relay K1 and the PTC resettable fuse F1 are connected in parallel with other battery cells for balancing.

[0058] This circuit design utilizes the coordinated operation of the battery cell, relay K1, PTC resettable fuse F1, and optocoupler U1. Under normal operating conditions, the battery cell can be connected to a multi-cell parallel circuit via the normally closed terminal of relay K1 and PTC resettable fuse F1. This allows it to participate in balancing synchronously with other cells, effectively ensuring the consistency of the state of charge and voltage of the multi-cell system and preventing single-cell imbalance from affecting overall energy storage efficiency. Furthermore, when a battery cell is reversed in polarity, the reverse current will trigger the PTC resettable fuse F1 to trip due to overcurrent heating, quickly cutting off the reverse circuit and preventing the large reverse current from damaging the battery cell or surrounding components, thus providing the first line of safety protection in case of reverse polarity connection. In addition, after the PTC resettable fuse F1 is blown, the optocoupler U1 senses the abnormal signal and drives the relay K1 to complete the polarity reversal. After the PTC resettable fuse F1 cools down and resets, the battery cell is reconnected to the parallel circuit through the normally open terminal of the relay K1. This not only corrects the polarity reversal problem but also avoids the equalization process from being interrupted due to polarity abnormalities. It ensures that the multi-cell parallel system can still restore the equalization function and maintain stable operation when polarity deviation occurs, which significantly improves the system's fault tolerance, safety, and equalization continuity, and protects the safety and lifespan of the battery cells during equalization.

[0059] The overall structure described above does not require complex control logic and relies solely on the characteristics of the components to achieve reverse connection protection. This simplifies circuit design, reduces hardware costs and the probability of failure, and can stably adapt to multi-cell parallel balancing scenarios. It provides highly reliable reverse protection and conduction stability for automatic balancing circuits, ensuring consistent and undamaged cell voltages after balancing, reducing balancing interruptions caused by faults in reverse connection protection modules, and effectively improving balancing efficiency.

[0060] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0061] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this application is in use. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In addition, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0062] Furthermore, terms such as "horizontal," "vertical," and "sag" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0063] In this application, unless otherwise expressly specified and limited, "above or below" a first feature may include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on" a first feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" a first feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0064] Although the description of this application has been made in conjunction with the specific embodiments described above, it is obvious to those skilled in the art that many substitutions, modifications, and variations can be made based on the above description. Therefore, all such substitutions, modifications, and variations are included within the spirit and scope of the appended claims.

Claims

1. A method of cell screening and grouping, comprising: The method comprises the steps of: S1, initial screening of the battery cell: a battery resistance tester is used to measure the voltage and internal resistance of the battery cell, and then an OCV software is used to sort the battery cell according to the set voltage, internal resistance, capacity and K value range, thereby forming a first echelon battery cell group; S2, secondary screening of the battery cell: the capacity of the first echelon battery cell group is graded and screened to form a second echelon battery cell group, the upper limit of the capacity of the second echelon battery cell group is set to , the lower limit of the capacity of the second echelon battery cell group is set to , and the second echelon battery cell group includes a plurality of capacity grade battery cell subgroups, each of which corresponds to a capacity range. S3, battery cell grouping: the battery cells in the capacity grade battery cell subgroups are grouped according to the requirements of the module string and parallel, thereby forming a third echelon battery cell group; S4, battery cell equalization assembly: the battery cells in the third echelon battery cell group are automatically equalized and assembled through an automatic equalization circuit.

2. The method of claim 1, wherein, Capacity difference of the second echelon battery cell group with the relationship: 。 3. The method of claim 2, wherein, In S2, the second echelon battery cell group comprises N capacity grade battery cell subgroups; wherein the N capacity grade battery cell subgroups are respectively a first capacity grade battery cell subgroup, a second capacity grade battery cell subgroup, and an Nth capacity grade battery cell subgroup.

4. The method of claim 3, wherein, The capacity range of the first capacity level sub-group of cells is : The capacity range of the second capacity level sub-group of cells is ; The capacity range of the Nth capacity level sub-group of battery cells is .

5. The method of claim 3, wherein, The second echelon battery cell group comprises four capacity grade battery cell subgroups; wherein the four capacity grade battery cell subgroups are respectively a first capacity grade battery cell subgroup, a second capacity grade battery cell subgroup, a third capacity grade battery cell subgroup and a fourth capacity grade battery cell subgroup. The first capacity grade battery cell subgroup has a plurality of battery cells a, the second capacity grade battery cell subgroup has a plurality of battery cells b, the third capacity grade battery cell subgroup has a plurality of battery cells c, and the fourth capacity grade battery cell subgroup has a plurality of battery cells d. In S3, the module grouping is performed in a T-string L-parallel structure, wherein T is the total number of battery cell series, and L is the total number of battery cell parallel branches.

6. The method of claim 5, wherein, When T , L , the module set has a relationship: X1+X2+ +X T ; wherein, X1, X2 X T is an electric core, X1+X2+ +X T is an electric core in series with T in number; The capacity grade of the battery cell satisfies any of the following modes: X1, X2 X T any one of the cells a or b, respectively; or X1, X2 X T each of the battery cells b or c; or X1, X2 X T each is any one of the cells c or d.

7. The method of claim 5, wherein, When T , L and L is even, the module set has the relationship one: ; and Equation Two: ; Wherein, Y1, Y2 Y n Respectively are parallel cell a and cell d; Z1, Z2 Z n Respectively are parallel cell b and cell c; the Is One With One Parallel.

8. The method of claim 5, wherein, When T , L and L is odd, the module set has the relationship one: and relation two: ; Wherein, the X1, X2 X n Respectively are any one of the battery cell a or the battery cell b or the battery cell c or the battery cell d; the Y1, Y2 Y n Respectively are the battery cell a and the battery cell d in parallel; the Z1, Z2 Z n Respectively are the battery cell b and the battery cell c in parallel; the Is One And One Parallel.

9. An automatic balancing circuit, characterized by The battery cell equalization assembly step suitable for the battery cell screening and grouping method according to any one of claims 1-8; The automatic equalization circuit comprises a plurality of battery polarity monitoring switching protection branch modules and a common power supply module, the plurality of battery polarity monitoring switching protection branch modules are connected in parallel, and the battery polarity monitoring switching protection branch modules are connected with the common power supply module, and the common power supply module is used to provide a unified power supply for the battery polarity monitoring switching protection branch modules.

10. The automatic balancing circuit according to claim 9, characterized in that, The battery polarity monitoring switching protection branch module comprises a battery unit, an optocoupler isolation unit, a relay polarity switching unit, an overcurrent protection unit and a battery polarity indication unit; The output end of the battery unit is connected with the input end of the optocoupler isolation unit; the output end of the optocoupler isolation unit is connected with the relay polarity switching unit, the battery polarity indication unit is connected between the relay polarity switching unit and the common power supply module, and the overcurrent protection unit is connected between the relay polarity switching unit and the overcurrent protection unit in other battery polarity monitoring switching protection branch modules.

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