Battery module
By setting parallel cell units and connecting resistors RS1 and RS2 in series in the battery module, the current ratio can be adjusted to achieve charge and discharge balance, which solves the overcharge and over-discharge problem caused by cell capacity differences, simplifies battery module design, reduces costs, and improves safety and performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- 东莞维科电池有限公司
- Filing Date
- 2025-03-20
- Publication Date
- 2026-05-15
AI Technical Summary
Existing battery modules suffer from overcharging or over-discharging problems due to differences in cell capacity and internal resistance during charging and discharging. Existing technical solutions increase complexity and cost and are not suitable for compact structural requirements.
By setting the first and second cell units in parallel in the battery module, and connecting resistors RS1 and RS2 in series in each cell unit, the current is adjusted to be proportional to the cell capacity. The current ratio is adjusted by using the series resistors to achieve charge and discharge balance.
It simplifies the internal structure of the battery module, reduces production costs and complexity, and improves the module's safety and performance utilization. It is suitable for application scenarios with significant differences in battery cells and capacities from different manufacturers.
Smart Images
Figure CN224249382U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the technical field of charging and discharging equipment, and specifically relates to a battery module. Background Technology
[0002] As the new energy market demands high capacity, low cost, and compact structure for lithium battery packs, the application of series and parallel designs with different cell capacities has become particularly important. To meet these product requirements, the market is increasingly emphasizing the differences in cell capacity. During charging, lower-capacity cells will fully charge first, sometimes even leading to overcharging; conversely, during discharging, lower-capacity cells will also deplete first, potentially causing over-discharging. Therefore, this design application places higher demands on cell selection, manufacturing, production processes, and protection board circuit design.
[0003] To meet the above requirements, various improvements have been made to battery modules and their internal protection circuits, including, but not limited to, methods such as voltage and internal resistance matching, balancing circuits, and introducing more auxiliary functions into the protection board circuit. However, these methods undoubtedly increase the difficulty of manufacturing processes for existing battery module components or reduce the space available for the battery module. In particular, the solution of requiring additional hardware devices and control logic for balancing circuits not only occupies more battery module space but also increases complexity. Therefore, further improvements to existing battery modules are needed to address these technical shortcomings. Utility Model Content
[0004] The purpose of this utility model is to address the shortcomings of existing technologies by providing a battery module that not only reduces the internal space occupied by the battery but also reduces the complexity of the internal manufacturing process of the battery module.
[0005] To achieve the above-mentioned objectives, this application implements the following technical solution:
[0006] A battery module includes a first battery cell unit and a second battery cell unit, wherein the first battery cell unit and the second battery cell unit are connected in parallel; the first battery cell unit includes a first battery cell group and a first resistor RS1 connected in series with the first battery cell group, and the second battery cell unit includes a second battery cell group and a second resistor RS2 connected in series with the second battery cell group.
[0007] The current carried by the first and second battery cell groups is proportional to the cell capacity of the first and second battery cell groups.
[0008] The current carried by the first battery cell group and the second battery cell is inversely proportional to the first impedance and the second impedance;
[0009] The first impedance is the sum of the first resistor RS1 and the internal resistance of the first cell group; the second impedance is the sum of the second resistor RS2 and the internal resistance of the second cell group.
[0010] The above technical solution produces the following technical effects:
[0011] To address the aforementioned technical deficiencies, this application proposes a battery module design, specifically comprising a first cell unit (first cell group + series-connected first resistor RS1) and a second cell unit (second cell group + series-connected second resistor RS2). By appropriately setting the series resistors RS1 and RS2, the current of each cell unit is adjusted so that its charging and discharging current is proportional to the cell capacity, thereby achieving charging and discharging balance for cells of different capacities.
[0012] As a further improvement to the battery module of this utility model, the first cell group, the second cell group, the first resistor RS1, and the second resistor RS2 satisfy the following:
[0013] =
[0014] Wherein, C1 is the cell capacity of the first cell group, C2 is the cell capacity of the second cell group, R1 is the internal resistance of the first cell group, and R2 is the internal resistance of the second cell group.
[0015] As a further improvement to the battery module of this utility model, the first cell group includes at least two first cells of the same capacity and model, and the second cell group includes at least two second cells of the same capacity and model. The first cells and the second cells have different capacities; the number of first cells is the same as the number of second cells.
[0016] As a further improvement to the battery module of this utility model, the number of first cells is 3 and the number of second cells is 3.
[0017] As a further improvement to the battery module of this utility model, the resistance value of the first resistor RS1 is greater than or equal to 0mΩ, and the resistance value of the second resistor RS2 is greater than or equal to 0mΩ.
[0018] As a further improvement to the battery module of this utility model, the resistance of the first resistor RS1 is 0mΩ.
[0019] As a further improvement to the battery module of this utility model, the resistance value of the second resistor RS2 is 0mΩ.
[0020] As a further improvement to the battery module of this utility model, the package type of the first resistor RS1 and the second resistor RS2 is any one of 0805, 1206, 1210, 2010, and 2512.
[0021] As a further improvement to the battery module of this utility model, the rated power of the first resistor RS1 and the second resistor RS2 is 1W-2W.
[0022] As a further improvement to the battery module of this utility model, both the first resistor RS1 and the second resistor RS2 are alloy resistors. Attached Figure Description
[0023] The accompanying drawings, which are included to provide a further understanding of the present invention and constitute a part of this invention, illustrate exemplary embodiments of the present invention and are used to explain the present invention, but do not constitute an undue limitation of the present invention. In the drawings:
[0024] Figure 1 This is one of the structural schematic diagrams of Embodiment 1 of this utility model;
[0025] Figure 2 This is a second structural schematic diagram of Embodiment 1 of this utility model;
[0026] Figure 3 This is the third structural schematic diagram of Embodiment 1 of this utility model;
[0027] Figure 4 This is one of the simulation principle diagrams for Embodiment 2 of this utility model;
[0028] Figure 5 This is the second simulation principle diagram of Embodiment 2 in this utility model;
[0029] in:
[0030] 1-First cell unit;
[0031] 11-First cell pack;
[0032] 111 - First battery cell;
[0033] 2-Second battery cell unit;
[0034] 21 - Second cell pack;
[0035] 211 - Second cell. Detailed Implementation
[0036] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terminology used in the specification of this application is for the purpose of describing specific embodiments only and is not intended to limit this application.
[0037] In the description of this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing" 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 utility model based on the specific circumstances.
[0038] Although this application discloses preferred embodiments as described above, it is not intended to limit the claims. Any person skilled in the art can make several possible changes and modifications without departing from the concept of this application. Therefore, the scope of protection of this application should be determined by the scope defined in the claims of this application.
[0039] The present invention will be further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.
[0040] Implementation Method 1
[0041] As the demand for high-capacity, low-cost, and compact lithium-ion battery packs in the new energy market continues to increase, multi-cell series-parallel combinations are widely used as a common design method in battery modules. However, due to the differences in parameters such as capacity and internal resistance among multiple cells, multi-cell series-parallel designs can lead to a series of problems. During charging, cells with smaller capacities, due to their lower energy storage capacity, will reach full charge first, potentially causing overcharging. Overcharging can cause a sharp increase in internal pressure within the cell, which may damage cell performance or even pose safety hazards.
[0042] During discharge, smaller capacity cells will deplete first due to their lower capacity, potentially leading to over-discharge. Over-discharge causes the cell voltage to drop below the safe lower limit, resulting in permanent damage or capacity decay. These issues not only reduce the overall lifespan and safety of the battery module but also make it difficult to utilize the actual total capacity of the battery, thus reducing the module's performance utilization rate.
[0043] While ideally each cell in a battery module should have completely identical capacity and parameters, differences in manufacturing processes, aging rates, and cell origins make capacity and internal resistance variations between cells unavoidable in practical applications. Existing technologies have devised various solutions to achieve charge-discharge balance among cells connected in series and parallel within a battery module. Among these, the most widely used solutions include: voltage and internal resistance matching methods, balancing circuit methods, and introducing more auxiliary functions into the protection board circuit.
[0044] Furthermore, the voltage and internal resistance matching method primarily groups cells with similar capacities to ensure that the parameters of the cells in the module are as close as possible (e.g., similar capacity ratio and internal resistance ratio). For cells with significant differences in capacity and internal resistance, formula optimization or improved manufacturing processes are used to adjust the chemical composition to achieve uniform internal resistance and capacity. However, this solution requires all cells to come from the same manufacturer and strictly control the matching degree of cell capacity and internal resistance, increasing production difficulty and cost. Simultaneously, this method requires cell parameters (such as capacity ratio and internal resistance ratio) to be within a strict predictable range, lacking flexibility and making it difficult to adapt to situations where cell parameters vary significantly in reality. Therefore, due to the need for strict matching, cells from different manufacturers cannot be directly connected in series or parallel, limiting design space and supply chain flexibility.
[0045] Furthermore, the solution for balancing circuits primarily involves introducing balancing circuits into the module to dynamically adjust each cell through active or passive balancing. By adding hardware circuitry, additional current is diverted to larger capacity cells or compensated for smaller capacity cells, ensuring synchronized charging and discharging of different cells. However, considering that balancing circuits require additional hardware components and control logic, they occupy more space in the battery module and increase complexity. Therefore, the design and production of balancing circuits using the above technical solutions not only require increased R&D investment but also significantly increase production costs, especially in compact small modules. Moreover, the introduction of more components introduces potential failure points, increasing the risk of instability in module operation and affecting long-term performance.
[0046] Furthermore, introducing more auxiliary functions into the protection board circuit, such as current control, to achieve charge-discharge balance by dynamically adjusting the current flow to different cells, has become one of the solutions for most manufacturers to achieve charge-discharge balance of cells within the battery module. However, auxiliary circuits usually require additional power supply, control chips, and a larger protection board area, making them unsuitable for module designs with high requirements for structural compactness. The addition of complex functions also leads to a significant increase in the cost and space requirements of the entire battery module, contradicting the demands for low cost and compact design.
[0047] To solve the above technical problems, such as Figures 1-3 As shown, this application improves upon existing battery modules. The improved battery module includes a first cell unit 1 and a second cell unit 2, which are connected in parallel. The first cell unit 1 includes a first cell group 11 and a first resistor RS1 connected in series with the first cell group 11. The second cell unit 2 includes a second cell group 21 and a second resistor RS2 connected in series with the second cell group 21. The current carried by the first cell group 11 and the second cell group 21 is proportional to their cell capacity. Specifically, this paper proposes a battery module design that includes a first cell unit 1 (first cell group 11 + first resistor RS1 connected in series) and a second cell unit 2 (second cell group 21 + second resistor RS2 connected in series). By appropriately setting the series resistors RS1 and RS2, the current of each battery cell unit is adjusted so that the current carried by the first and second battery cell groups is directly proportional to the cell capacity of the first and second battery cell groups; the current carried by the first and second battery cell groups is inversely proportional to the first resistor RS1 and the second resistor RS2. This achieves charge and discharge balance for battery cells of different capacities.
[0048] The following comparative analysis will illustrate the advantages of the technical solution of this application compared with traditional technical solutions.
[0049] This application is based on physical formulas:
[0050]
[0051] By controlling the values of the series resistors RS1 and RS2 in the first battery cell unit 1 and the second battery cell unit 2, the total impedance of each unit is adjusted to ensure that:
[0052] That is, by adjusting the current ratio flowing through different battery cells to make it proportional to their capacity, synchronous charging and discharging can be achieved. Compared to balancing circuits and auxiliary function designs, this solution achieves current regulation through a simple series resistor design, avoiding the need for additional balancing chips or protection circuits, thus saving space and reducing costs.
[0053] Furthermore, compared to existing solutions, which have more complex equalization circuits and require large protection boards for auxiliary functions, thus occupying module space, the technical solution of this application achieves the technical effect of simply adjusting the current ratio through series resistors and having a simple circuit design. At the same time, in terms of applicability, existing technical solutions require strict capacity ratio and internal resistance ratio, and require cells from the same manufacturer to be connected in series and parallel, while the technical solution of this application is applicable to cells from different manufacturers with large capacity differences, and has extremely strong compatibility.
[0054] Furthermore, the principle of the technical solution in this application is based on the fact that the battery capacity C is usually expressed in ampere-hours (Ah) or milliampere-hours (mAh), representing the time the battery can continuously discharge under a certain current. The relationship between battery capacity and current satisfies:
[0055]
[0056] Where: C is the battery capacity, I is the current through the battery, and t is the charging and discharging time.
[0057] Therefore, in order to simultaneously charge or discharge battery cells of different capacities within the same time frame, it is necessary to adjust the current carried by each cell to ensure their discharge times are consistent. Thus, to achieve charge-discharge balance, the current carried by each cell must be proportional to its capacity, i.e.: In this way, the larger capacity cell C1 carries a larger current I1, and the smaller capacity cell C2 carries a smaller current I2, ensuring that they complete charging and discharging in the same amount of time.
[0058] Furthermore, an external resistor RS1 and RS2 are connected in series in the circuit of each cell. By adjusting the resistance values of these two resistors, the total resistance of each circuit is changed, thereby regulating the current flowing through each cell.
[0059] According to Ohm's law, the current I can be expressed as:
[0060]
[0061] Where V is the battery voltage, and the total R is always the sum of the series resistance and the internal resistance of the battery cell.
[0062] For two battery cells of different capacities, the discharge balance condition is:
[0063]
[0064] Therefore, substituting the two current ratios above into the equilibrium condition, we can obtain:
[0065]
[0066] The above formula indicates that by adjusting the resistance values of RS1 and RS2, I1 and I2 can be controlled to achieve charge-discharge balance for cells of different capacities. Therefore, applying the above formula to the technical solution of this application, it can be seen that the first cell group 11, the second cell group 21, the first resistor RS1, and the second resistor RS2 satisfy the following:
[0067]
[0068] Wherein, C1 is the cell capacity of the first cell group 11, C2 is the cell capacity of the second cell group 21, R1 is the internal resistance of the first cell group 11, and R2 is the internal resistance of the second cell group 21.
[0069] In the specific implementation process, assuming RS1 is known, RS1 is gradually increased from zero, and the corresponding RS2 is calculated by substituting it into the formula until RS2 is a positive value. This ensures that the external resistance is reasonable. For example, if the battery module uses different cell capacities C1 (1000mAh) and C2 (500mAh), and the cell internal resistances are R1 (60mΩ) and R2 (80mΩ), when calculating RS1 and RS2, RS1 is first substituted with 0. The formula is:
[0070]
[0071] Therefore, RS2 is calculated to be negative, which does not meet the requirements. Further, RS1 needs to be substituted with 1 and recalculated until RS2 becomes positive. The calculation shows that when RS1 is 40, RS2 = 0, meaning the required resistance values are RS1 (40mΩ) and RS2 (0mΩ). This example does not mean the calculation ends only when either RS1 or RS2 reaches 0mΩ; specifically, even if one RS1 or RS2 is known, the other may not be 0mΩ.
[0072] Implementation Method 2
[0073] To further demonstrate the internal structural stability of the battery module in this application compared to traditional battery modules, further, such as Figures 1-5 As shown: the first cell group 11 includes at least two first cells 111 of the same capacity and model, and the second cell group 21 includes at least two second cells 211 of the same capacity and model. The first cells 111 and the second cells 211 have different capacities, and the number of first cells 111 and the number of second cells 211 are the same. Figure 4The first battery cell group 11 includes two first battery cells 111 with the same capacity and model, and the second battery cell group 21 includes two second battery cells 211 with the same capacity and model. Each first battery cell 111 has the same specifications and parameters, and each second battery cell 211 also has the same specifications and parameters.
[0074] Therefore, the first cell group 11 and the second cell group 21 are composed of cell units with the same structure, making the internal structure of the battery module more uniform and improving the overall structural stability of the module. At the same time, since the capacity difference between cell units can be balanced by series resistors, cell units can come from different manufacturers, relaxing the restrictions on cell sources and enhancing the flexibility of the supply chain and the freedom of module design.
[0075] In practical implementation, battery module designers can flexibly adjust the number of cells in the first cell group 11 and the second cell group 21, as well as the resistance values of the series resistors RS1 and RS2, according to actual needs and cell specifications, to achieve optimal charge-discharge balance. This design not only simplifies the internal structure of the battery module and reduces production costs, but also improves the module's safety and performance utilization, providing a more efficient and reliable battery module solution for the new energy market.
[0076] Furthermore, such as Figure 5 As shown, the number of first cells 111 is 3, and the number of second cells 211 is 3. At this time, the first cell unit 1 and the second unit achieve the optimal cell quantity relationship, which is the optimal embodiment of this application.
[0077] Furthermore, the package types of the first resistor RS1 and the second resistor RS2 are any one of 0805, 1206, 1210, 2010, and 2512. It should be noted that the package types such as 0805, 1206, 1210, 2010, and 2512 are standard specifications for surface mount devices (SMD). These package types are primarily used to define the external dimensions of the resistors.
[0078] Furthermore, the power ratings of the first resistor RS1 and the second resistor RS2 are 1W-2W. It is worth noting that resistors with a power rating around 1W have lower costs and are more suitable for battery module designs where cost savings are required; while when the power rating of the resistor reaches around 2W, its cost is higher than that of resistors with a power rating around 1W, but it brings better heat dissipation performance and is more suitable for battery module designs where heat dissipation performance is important.
[0079] Furthermore, both the first resistor RS1 and the second resistor RS2 are made of thick-film or thin-film alloy resistors. Alloy resistors, also known as precision resistors, are denoted by RS. Therefore, alloy resistors possess characteristics such as high precision, low temperature coefficient, high stability, and high power, making them suitable for the precise current regulation requirements of the technical solution in this application. By using alloy resistors as series resistors RS1 and RS2, this application can ensure the stability and accuracy of the current during the charging and discharging process of the battery module, further improving the module's safety and performance utilization.
[0080] Other aspects that are the same as in Implementation Method 1 will not be described again in this implementation method.
[0081] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A battery module, comprising a first cell unit (1) and a second cell unit (2), wherein the first cell unit (1) and the second cell unit (2) are connected in parallel; characterized in that, The first cell unit (1) includes a first cell group (11) and a first resistor RS1 connected in series with the first cell group (11); the second cell unit (2) includes a second cell group (21) and a second resistor RS2 connected in series with the second cell group (21). The current carried by the first cell group (11) and the second cell group (21) is proportional to the cell capacity of the first cell group (11) and the second cell group (21); The current carried by the first cell group (11) and the second cell group (21) is inversely proportional to the first impedance and the second impedance; The first impedance is the sum of the first resistor RS1 and the internal resistance of the first cell group (11); the second impedance is the sum of the second resistor RS2 and the internal resistance of the second cell group (21).
2. A battery module according to claim 1, characterized in that, The first cell group (11), the second cell group (21), the first resistor RS1, and the second resistor RS2 satisfy the following: = Wherein, C1 is the cell capacity of the first cell group (11), C2 is the cell capacity of the second cell group (21), R1 is the cell internal resistance of the first cell group (11), and R2 is the cell internal resistance of the second cell group (21).
3. A battery module according to claim 1, characterized in that, The first cell group (11) includes at least two first cells (111) of the same capacity and model, and the second cell group (21) includes at least two second cells (211) of the same capacity and model, wherein the first cells (111) and the second cells (211) have different capacities; The number of the first battery cell (111) is the same as the number of the second battery cell (211).
4. A battery module according to claim 3, characterized in that, The number of the first battery cell (111) is 3, and the number of the second battery cell (211) is 3.
5. A battery module according to claim 1, characterized in that, The resistance of the first resistor RS1 is greater than or equal to 0 mΩ, and the resistance of the second resistor RS2 is greater than or equal to 0 mΩ.
6. A battery module according to claim 5, characterized in that, The resistance of the first resistor RS1 is 0mΩ.
7. A battery module according to claim 5, characterized in that, The resistance of the second resistor RS2 is 0mΩ.
8. A battery module according to claim 1, characterized in that, The first resistor RS1 and the second resistor RS2 are packaged in any one of the following packages: 0805, 1206, 1210, 2010, and 2512.
9. A battery module according to claim 1, characterized in that, The rated power of the first resistor RS1 and the second resistor RS2 is 1W-2W.
10. A battery module according to claim 1, characterized in that, Both the first resistor RS1 and the second resistor RS2 are alloy resistors.