Battery pack protection device

Abstract

The battery pack protection device comprises battery brackets which are arranged at two ends of a battery pack and are used for supporting and fixing the battery pack, printed boards which are fixed with the battery brackets, and current-limiting nickel straps which are fixed between electrodes of single batteries and the printed boards, the current limiting nickel strap comprises a single battery welding area connected with an electrode of a single battery, a confluence welding area connected with the printed board, and a current limiting area connected with the single battery welding area and the confluence welding area; and the printed board comprises a circuit for connecting each single battery in the battery pack and an output electrode of the battery pack. According to the invention, the bottom of the cell stack is connected by adopting a printed board and a current-limiting nickel strap. The current-limiting nickel strap is provided with a current-limiting area, long-time normal work can be ensured under the working condition, and when the battery encounters external short circuit, the current-limiting area is fused, so that the safety problem of the battery can be avoided.

Description

Technical Field

[0001] The present invention relates to the field of lithium-ion battery pack safety design, and in particular to a battery pack protection device. Background Art

[0002] In the aerospace sector, 18650 lithium-ion battery packs are widely used due to their high energy density and relatively light weight. However, with growing concerns about battery pack safety, particularly in extreme environments and during long missions, the role of battery management systems (BMS) has become increasingly crucial. Currently, many BMSs in aerospace applications primarily monitor battery status, including real-time monitoring of parameters such as voltage, temperature, and charge and discharge status. This single monitoring function somewhat limits their ability to proactively intervene in battery pack safety.

[0003] During space missions, battery packs face extreme environmental factors such as high temperatures, low temperatures, and radiation. These factors can degrade battery performance, shorten battery life, and even lead to safety incidents. Therefore, relying solely on monitoring without an effective command and control mechanism is unable to promptly address potential safety hazards. When battery temperatures rise abnormally, the battery pack cannot proactively take measures, such as limiting charging current or disconnecting the power supply, to prevent thermal runaway.

[0004] Therefore, how to improve the safety of 18650 lithium-ion battery packs in the aerospace field and enable them to have active intervention and control capabilities is a technical problem that needs to be urgently solved in the field of lithium-ion battery pack safety design. Summary of the Invention

[0005] In order to solve the problems of low safety performance and lack of active intervention and control capabilities in the existing 18650 lithium-ion battery pack, the present invention provides a battery pack protection device, comprising: battery holders arranged at both ends of the battery pack to support and fix the battery pack, a printed circuit board fixed to the battery holder, and a current-limiting nickel strip fixed between the electrodes of the single battery and the printed circuit board;

[0006] The current-limiting nickel strip includes: a single cell welding area connected to the electrode of the single cell, a busbar welding area connected to the printed circuit board, and a current-limiting area connecting the single cell welding area and the busbar welding area;

[0007] The printed circuit board includes a circuit for connecting each single battery in the battery pack and an output electrode of the battery pack.

[0008] Preferably, the printed circuit board substrate includes an epoxy board and a busbar area fixed to the epoxy board.

[0009] Preferably, a copper-nickel-plated metal layer is provided on the surface of the epoxy board.

[0010] Preferably, the single cell welding area includes a welding piece adapted to the size of the single cell and a long groove arranged in the middle of the welding piece.

[0011] Preferably, the structure of the flow-limiting area is strip-shaped.

[0012] Preferably, the series-parallel connection of the single cells includes spot welding of mesh nickel strips.

[0013] Preferably, the thickness of the flow limiting area is 0.1 to 0.2 mm.

[0014] Preferably, the width of the flow-limiting area is 0.5-1 mm.

[0015] Preferably, the welding process of the current-limiting nickel strip includes at least one of resistance welding and laser welding.

[0016] Preferably, the edges and middle of the battery holder are designed with clips to fix the printed circuit board on the end face of the battery stack.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention provides a battery pack protection device, comprising: battery holders arranged at both ends of the battery pack and supporting and fixing the battery pack, a printed circuit board fixed to the battery holder, and a current-limiting nickel strip fixed between the electrodes of the single cell and the printed circuit board; the current-limiting nickel strip comprises: a single cell welding area connected to the electrodes of the single cell, a busbar welding area connected to the printed circuit board, and a current-limiting area connecting the single cell welding area and the busbar welding area; the printed circuit board comprises a circuit for connecting each single cell in the battery pack and the output electrode of the battery pack. The current-limiting nickel strip is designed with a current-limiting area to ensure long-term normal operation under working conditions. When the battery encounters an external short circuit, the current-limiting area melts, thereby avoiding safety problems of the battery. The current-limiting nickel strip structure includes three parts: a single cell welding area, a current-limiting area, and a busbar welding area. The single-cell welding area is primarily used to connect the current-limiting nickel strip to the single-cell battery, with a long groove in the middle designed to increase welding reliability. The busbar welding area is primarily used to connect the current-limiting nickel strip to the busbar area. The current-limiting area is designed to be a special shape, and its current capacity can meet the operating conditions and derating requirements. At the same time, when a single cell has a safety problem such as a short circuit or overcurrent, the current-limiting area can be ensured to fuse in time, disconnecting the problematic cell without affecting the remaining cells, thereby ensuring the safety of the other cells. The present invention has been verified through simulation pre-experiments, fully verifying its feasibility and achieving significant results. It can be applied to space energy storage and space portable energy storage systems.

[0019] The present invention utilizes a current-limiting nickel strip to limit further current increases when current increases abnormally, effectively preventing damage to the battery pack due to overcurrent. The current-limiting area of the nickel strip automatically fuses or limits the current when the current exceeds a set value, avoiding safety hazards caused by short circuits or overcurrent, such as battery overheating, fire, or explosion. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the overall structure of the battery pack protection device of the present invention;

[0021] Figure 2 This is a schematic diagram of the structure of the current-limiting nickel strip of the present invention;

[0022] Figure 3 A schematic diagram of a partial structure of a battery pack protection device according to the present invention;

[0023] Figure 4 This is a schematic diagram of the battery bracket structure of the present invention;

[0024] Figure 5 This is a schematic diagram of the upper battery bracket structure of the present invention;

[0025] Figure 6 This is a schematic diagram of the lower battery bracket structure of the present invention;

[0026] Figure 7 A three-dimensional schematic diagram of a battery holder according to the present invention;

[0027] Figure 8 A schematic diagram of a printed circuit board of the present invention;

[0028] Figure 9 This is a discharge curve diagram of the battery stack before the short-circuit test of the present invention;

[0029] Figure 10 This is a curve diagram of the opening voltage change when the battery stack of the present invention is short-circuited;

[0030] Figure 11 Velocity field distribution diagram when the current limiting area width is 0.5mm and the working state is 2.2A;

[0031] Figure 12 Velocity field distribution diagram when the current limiting area width is 0.5mm and the working current is 20A;

[0032] Figure 13 Velocity field distribution diagram when the current limiting area width is 0.6mm and the working state is 2.2A;

[0033] Figure 14 Velocity field distribution diagram when the current limiting area width is 0.6mm and the working current is 20A;

[0034] Figure 15Velocity field distribution diagram when the current limiting area width is 0.8mm and working at 2.2A;

[0035] Figure 16 Velocity field distribution diagram when the current limiting area width is 0.8mm and the working current is 20A;

[0036] Figure 17 Velocity field distribution diagram when the current limiting area width is 1mm and the working state is 2.2A;

[0037] Figure 18 Velocity field distribution diagram when the current limiting area width is 1mm and the working current is 20A;

[0038] 1-printed circuit board; 2-current limiting nickel strip; 3-single cell; 4-battery holder; 11-busbar area; 21-single cell welding area; 22-current limiting area; 23-busbar welding area; 41-upper battery holder; 42-lower battery holder; 43-clip. DETAILED DESCRIPTION

[0039] In order to better understand the present invention, the present invention is further described below with reference to the accompanying drawings and examples.

[0040] like Figures 1-8 As shown, a battery pack protection device includes: battery holders 4 provided at both ends of the battery pack to support and fix the battery pack, a printed circuit board 1 fixed to the battery holder 4, and a current-limiting nickel strip 2 fixed between the electrodes of the single battery 3 and the printed circuit board 1;

[0041] like Figure 3 As shown, the current-limiting nickel strip 2 includes: a single cell welding area 21 connected to the electrode of the single cell 3, a busbar welding area 23 connected to the printed circuit board 1, and a current-limiting area 22 connecting the single cell welding area 21 and the busbar welding area 23;

[0042] The printed circuit board 1 includes circuits for connecting the individual cells 3 in the battery pack and output electrodes of the battery pack.

[0043] When excessive current flows, the current-limiting region 22 of the current-limiting nickel strip 2 generates heat through its own resistance, causing it to melt or limit the current, thereby preventing safety issues caused by overcurrent in the battery pack. In the event of a short circuit, the current-limiting nickel strip 2 can quickly disconnect the circuit, preventing serious damage to the battery pack caused by the short-circuit current. The circuitry on the printed circuit board 1 monitors the voltage of each cell 3 within the battery pack, preventing overcharging or over-discharging of the cells 3, thereby extending battery life and avoiding safety hazards caused by voltage anomalies. Furthermore, the printed circuit board 1 supports and secures the battery pack, providing stable mechanical support and reducing damage to the battery pack due to vibration or external forces during use.

[0044] The present invention innovatively connects the battery stack using a printed circuit board 1 and a current-limiting nickel ribbon 2 at the bottom. The current-limiting nickel ribbon 2 is designed with a current-limiting region 22, ensuring long-term normal operation under working conditions. If the battery experiences an external short circuit, the current-limiting region 22 fuses, preventing battery safety issues.

[0045] The current limiting region 22 of the current limiting nickel strip 2 has an overcurrent fusing characteristic. When an external short circuit occurs in the battery, the current limiting region 22 of the current limiting nickel strip 2 will quickly fuse to ensure the safety of the battery.

[0046] A design method for a high-temperature-melting nickel ribbon for connecting batteries based on the safety of lithium-ion batteries includes nickel ribbon size selection, nickel ribbon shape design, and a printed circuit board 1 + current-limiting nickel ribbon 2 method.

[0047] The printed circuit board 1 + current-limiting nickel strip 2 method is used to connect the bottom of the battery stack. The printed circuit board 1 base material is an epoxy board, and the surface is etched with a copper-plated nickel metal layer according to the circuit direction, which serves as the battery stack series and parallel bus area 11.

[0048] The printed circuit board 1 substrate includes an epoxy board and a busbar area 11 fixed to the epoxy board.

[0049] The epoxy board has excellent insulation properties, effectively preventing short circuits within the battery pack and improving its safety. It also prevents electrolyte leakage and, thanks to its chemical resistance, protects against erosion by internal battery chemicals and external moisture. It also provides strong mechanical support for the battery pack, absorbing external vibration and pressure to maintain its stability. The design of the confluence area 11 ensures stable electrical connections between the individual cells 3 within the battery pack, reducing the risk of poor contact or loose connections.

[0050] The surface of the epoxy board is provided with a copper-nickel-plated metal layer.

[0051] The nickel layer has a strong passivation ability and can quickly form a dense passivation film on the surface, effectively resisting corrosion from the atmosphere, humid environments, and certain acidic or alkaline substances. This property enables the copper-nickel plating layer to maintain good performance even in harsh environments, extending the service life of the battery pack protection device. At the same time, the nickel plating layer has high hardness and excellent wear resistance, which enables the copper-nickel plating metal layer to better withstand mechanical friction and wear, protecting the epoxy board surface from damage, thereby improving the durability of the entire battery pack protection device. Copper itself has good conductivity, and the addition of the nickel layer can further enhance the stability and reliability of the conductive performance. This design helps optimize the battery pack's electrical connections, reduce contact resistance, and improve the battery pack's charge and discharge efficiency.

[0052] The single cell welding area 21 includes a welding piece adapted to the size of the single cell 3 and a long groove arranged in the middle of the welding piece.

[0053] The long slot increases weld path flexibility, allowing welding equipment to perform multi-point or continuous welding within the slot, further enhancing weld strength. The long slot design disperses welding heat, preventing localized overheating from damaging the battery electrodes while also reducing thermal stress and deformation. The compatible welding tab and long slot design facilitates the positioning and operation of automated welding equipment, improving production efficiency and consistency.

[0054] The structure of the flow limiting area 22 is strip-shaped.

[0055] The current-limiting region 22 achieves uniform current distribution through a complex geometric structure, avoiding localized overcurrent, thereby improving the stability and safety of the battery pack. The tapered strip-shaped structure optimizes the flow field, reduces pressure loss, and improves the current-limiting effect. Furthermore, the strip-shaped structure can be designed through topological optimization to reduce stress concentration points in the structure and improve overall stability.

[0056] The series and parallel connection modes of the single cells all include spot welding of mesh nickel strips.

[0057] The thickness of the flow restriction area 22 is comprised between 0.1 and 0.2 mm.

[0058] The width of the flow restriction area 22 is comprised between 0.5 and 1 mm.

[0059] The welding process of the current-limiting nickel strip 2 includes at least one of resistance welding and laser welding.

[0060] The edges and middle of the battery holder 4 are designed with clips 43 to fix the printed circuit board 1 on the end surface of the battery stack.

[0061] Laser welding provides high-precision, highly stable welds with dense weld structure, a small heat-affected zone, and joint strength close to that of the base material. This welding method is particularly suitable for high-melting-point metals such as nickel alloys, minimizing thermal deformation and damage during welding. Resistance welding offers high speed and efficiency, resulting in smooth, aesthetically pleasing welds without spatter. Furthermore, resistance welding is applicable to a wide variety of metal materials and shapes, ensuring consistent weld quality.

[0062] The edges and middle of the battery holder 4 are designed with clips 43 to fix the printed circuit board 1 on the end surface of the battery stack.

[0063] In order to ensure the stability of the battery stack and keep a certain distance between each single battery 3 as much as possible within a limited space to ensure that the single batteries 3 do not directly contact each other, which is conducive to heat dissipation between the single batteries 3 and to avoid mutual influence between the single batteries 3 as much as possible, an integral bracket is designed to fix the battery stack to ensure that there is no relative displacement between the single batteries 3 in a mechanical environment.

[0064] The selection of bracket materials prioritized strength and light weight, followed by good resistance to high and low temperatures. Furthermore, given the long battery life, the material also required good aging resistance. After comprehensive evaluation, the battery bracket 4 was made of a special engineering plastic, which exhibits excellent insulation, high temperature resistance (300°C), low temperature resistance (-100°C), and high strength. Due to its excellent aging resistance, special engineering plastics maintain their mechanical and chemical stability over time, making them widely used in various industrial fields. For example, in harsh environments such as high temperatures (300°C), low temperatures (-100°C), high pressure, and corrosion, they can replace metal materials, improving equipment reliability and service life. Furthermore, they offer excellent wear and fatigue resistance, allowing for long-term use under high loads and high frequencies. Their high strength and lightweight properties make them an ideal choice for applications in the aerospace, automotive, and petrochemical industries. Furthermore, this material exhibits excellent electrical insulation and radiation resistance, making it widely applicable in various fields, including the power, electronics, and nuclear industries.

[0065] like Figure 4-Figure 8 As shown, the battery holder 4 includes an upper battery holder 41 and a lower battery holder 42. The 11-parallel-7-series connection method is selected, with 11 parallels forming a module and then connected in series. A three-dimensional schematic diagram of the overall holder is designed based on the battery shape and the arrangement of the internal single cells 3.

[0066] The hole spacing between each circular hole inside the bracket is 19.0mm×19.5mm.

[0067] After the battery stack is fixed and assembled, the spacing between the individual cells (3) in each row is 0.5 mm, and the spacing between the individual cells (3) in each column is 1 mm. The battery holders (4) isolate the individual cells (3), preventing direct contact between them and facilitating heat dissipation. Furthermore, within the limited space, the cells (3) are minimized from interfering with each other in the event of thermal runaway or short circuits.

[0068] The top of the battery stack and the three-dimensional schematic diagram of the battery stack are as follows Figure 7 shown.

[0069] Single cell 3 connection strip design:

[0070] After the battery stack is fixed with an integral bracket, one side (the top) is connected in series and parallel using the nickel strip welding method commonly used in the industry.

[0071] The three-series-parallel connection of 18650 cylindrical single cells commonly used in the lithium-ion battery industry is achieved by using mesh nickel strip spot welding.

[0072] One side of the battery stack uses a 0.1mm×6mm nickel ribbon for series and parallel connection. Each 0.1mm×6mm nickel ribbon has a rated current of 6A. Based on the battery stack structure, each 11 cells are connected in parallel to form a module using 0.1mm×6mm nickel ribbon. Seven modules are connected in series using 0.1mm×6mm nickel ribbon. Each module has five series ribbons, spaced 16mm apart to prevent interference. Each ribbon is rated for 6A, and the total rated current of the five ribbons in parallel in the series circuit is 30A. The actual maximum operating current of the battery is 12A, with a derating factor of 0.4, meeting Level I derating.

[0073] Design of printed circuit board 1 and current-limiting nickel strip 2:

[0074] The other side (bottom) of the battery stack is connected using a printed circuit board 1 and a current-limiting nickel strip 2. The printed circuit board 1 is an epoxy board with a copper-nickel-plated metal layer etched on the surface according to the circuit direction, which serves as the battery stack series and parallel busbar area 11.

[0075] The battery holder 4 is designed with buckles 43 on the edge and middle to fix the printed circuit board 1 on the end face of the battery stack. Figure 1 .

[0076] The size of the busbar metal area of PCB 1 is t0.2mm×5mm, the rated working current is 10A, the number of nickel strips in the busbar area in the current transmission direction is 4, the interval between the nickel strips is 17mm, and they do not affect each other. The total rated current of the 4 strips is 40A, reaching the level I derating. Figure 1 The arrows in the figure show the direction of current transfer in the battery stack.

[0077] The copper-nickel-plated metal layer is etched on the current-limiting nickel strip 2. When connecting, the current-limiting nickel strip 2's busbar area 11 is first resistance-welded to the printed circuit board 1. The printed circuit board 1 acts as a support and insulation. Then, the printed circuit board 1 is placed on the bottom of the battery stack. The current-limiting nickel strip 2's single-cell welding area 21 is then welded to the single-cell 3 in sequence. See the schematic diagram of the current-limiting strip on the battery stack printed circuit board 1 below. Figure 1 .

[0078] The current-limiting nickel strip 2 mainly plays the role of overcurrent fuse. According to the maximum operating current of the battery of 12A, the average maximum overcurrent of each single battery 3 of the 11 parallel batteries is 1.1A (12÷11). Considering the current level I derating, the derating factor is at least 0.5. Therefore, the minimum overcurrent of the current-limiting nickel strip 2 needs to reach 1.1÷0.5=2.2A.

[0079] The current limiting nickel strip 2 structurally includes three parts: a single cell welding area 21, a current limiting area 22, and a busbar welding area 23. Figure 2 As shown, the single cell welding area 21 is mainly used for connecting the current-limiting nickel strip 2 with the single cell 3, and a long groove is designed in the middle to increase welding reliability; the confluence welding area 23 is mainly used for connecting the current-limiting nickel strip 2 with the confluence area 11; the current-limiting area 22 is designed to be special-shaped, and its current-carrying capacity can meet the working conditions and derating requirements. At the same time, when a single single cell 3 has safety problems such as short circuit and overcurrent, it can ensure that the current-limiting area 22 is melted in time, so that the problem battery is disconnected and the remaining batteries are not affected, thereby ensuring the safety of other single cells 3.

[0080] The cross-sectional area of the single cell welding area 21 and the busbar welding area 23 is larger than t0.1mm×6mm, and the rated current is 6A, which can meet the Class I derating. To ensure reliable fusing, the current-limiting nickel strip 2 needs to control the line resistance of the current-limiting area 22, and control its overcurrent capacity to 2.2A. At the same time, it needs to ensure reliable fusing under high current conditions. Therefore, the current-limiting area 22 of the current-limiting nickel strip 2 is designed as a special-shaped area. The schematic diagram of the current-limiting nickel strip 2 is shown below. Figure 2 .

[0081] Nickel Strip Size Options:

[0082] The width of the nickel strip is designed according to the required current. After the battery stack is fixed with an integral bracket, one side (the top) is connected in series and parallel using the nickel strip welding method commonly used in the industry.

[0083] The three-series-parallel connection of 18650 cylindrical single cells commonly used in the lithium-ion battery industry is achieved by using mesh nickel strip spot welding.

[0084] Common nickel strip specifications include t0.1mm×6mm (width), t0.1mm×10mm (width), t0.15mm×6mm (width), t0.15mm×10mm (width), etc.

[0085] Limited by the diameter of the positive cap of the 18650 single cell battery (7mm),

[0086] Usually 6mm wide nickel strip is used for 18650 single battery3;

[0087] Nickel strips with a width of 10 mm are usually used in 26650 single cells3;

[0088] In terms of thickness, the thickness of the nickel strip is to ensure the overcurrent capacity of the battery pack. The thicker the thickness, the greater the overcurrent. However, the thicker the nickel strip, the greater the energy required for spot welding with the single battery 3. Spot welding with high current is prone to cold welding.

[0089] Since the normal working current of this battery is 3.2A and the maximum working current is 12A / 2s, the current is relatively small, so the nickel strip is selected with a thickness of t0.1mm with better welding performance.

[0090] Since the material and thickness paths are the same, controlling the line resistance of the current-limiting region 22 primarily involves controlling its width. In summary, a 0.1mm×6mm nickel ribbon is selected for series and parallel connection on one side of the battery stack. A 0.1mm×6mm nickel ribbon has a rated current of 6A. Based on the battery stack layout, each of the 11 cells 3 is connected in parallel using a 0.1mm×6mm nickel ribbon to form a module. Seven modules are connected in series using 0.1mm×6mm nickel ribbons. Each module has five series ribbons, spaced 16mm apart to prevent interference. Each ribbon is rated for 6A, and the total rated current of the five ribbons in parallel in the series circuit is 30A. The actual maximum operating current of the battery is 12A, with a derating factor of 0.4, achieving Class I derating. The structure is calculated based on current-limiting nickel ribbons 2 of varying widths.

[0091] Example 1

[0092] A battery pack protection device, comprising: battery holders 4 arranged at both ends of the battery pack to support and fix the battery pack, a printed circuit board 1 fixed to the battery holder 4, and a current-limiting nickel strip 2 fixed between the electrodes of the single battery 3 and the printed circuit board 1;

[0093] The current-limiting nickel strip 2 includes: a single cell welding area 21 connected to the electrode of the single cell 3, a busbar welding area 23 connected to the printed circuit board 1, and a current-limiting area 22 connecting the single cell welding area 21 and the busbar welding area 23;

[0094] The printed circuit board 1 includes circuits for connecting the individual cells 3 in the battery pack and output electrodes of the battery pack.

[0095] The printed circuit board 1 substrate includes an epoxy board and a busbar area 11 fixed to the epoxy board.

[0096] The surface of the epoxy board is provided with a copper-nickel-plated metal layer.

[0097] The single cell welding area 21 includes a welding piece adapted to the size of the single cell 3 and a long groove arranged in the middle of the welding piece.

[0098] The structure of the flow limiting area 22 is strip-shaped.

[0099] The series-parallel connection of the single cells all includes spot welding of mesh nickel strips.

[0100] The width of the flow restriction area 22 is 0.5 mm.

[0101] The thickness of the flow limiting area 22 is 0.1 mm

[0102] The welding process of the current-limiting nickel strip 2 is resistance welding.

[0103] The edges and middle of the battery holder 4 are designed with clips 43 to fix the printed circuit board 1 on the end surface of the battery stack.

[0104] Examples 2-5

[0105] The specifications of the nickel strips provided in Examples 2-5 are shown in Table 1:

[0106] Table 1 Nickel Strip Specifications and Processing

[0107] Example 2 Example 3 Example 4 Example 5 Current limiting nickel strip width 0.6 0.8 1 0.5 Current limiting nickel strip thickness 0.1 0.1 0.1 0.2 Current-limiting nickel strip welding process resistance welding resistance welding Laser welding Laser welding

[0108] Test Case

[0109] like Figure 10-18 As shown, ANSYS software is used to calculate the flow capacity of typical current limiting areas 22 with different widths. The results are shown in Table 2-3:

[0110] Table 2 Calculation results of current limiting nickel strip current limiting area 22

[0111]

[0112]

[0113] Table 3 Current-limiting nickel strip overcurrent test results

[0114] Nickel strip specifications Overcurrent value (A) Fuse time (s) Example 1 δ0.1mm×0.5mm(thickness×width) 12 0.8s circuit breaker Example 2 δ0.1mm×0.6mm(thickness×width) 12 1.5s circuit breaker Example 3 δ0.1mm×0.8mm(thickness×width) 18 1.6s circuit breaker Example 4 δ0.1mm×1mm(thickness×width) 20 1s fuse Example 5 δ0.2mm×0.5mm(thickness×width) 20 1s fuse

[0115] As shown in Table 1, the nickel strips within the specifications of Examples 1-5 can all be melted. However, considering the comprehensive equilibrium temperature and melting time, it is preferred that the width of the current-limiting nickel strip 2 is 0.8 mm as the width of the current-limiting region 22 .

[0116] An overcurrent test on a single current-limiting nickel strip 2 revealed that current-limiting region 22 would melt within 1.6 seconds when the current exceeded 18A. The battery pack discharge circuit consists of 11 cells connected in parallel, and the maximum current in the parallel circuit is 198A (18 x 11), causing all nickel strips to melt. A single cell 3 was subjected to an external short-circuit test, with a short-circuit current of approximately 110A, far exceeding the 18A melting current of a single current-limiting nickel strip 2, demonstrating reliable melting.

[0117] As shown in Table 2, when a safety problem such as a short circuit or overcurrent occurs in an individual single cell 3, the current limiting region 22 can be promptly blown to isolate the faulty cell. At this time, the number of parallel batteries is reduced from 11 to 1 without affecting the power supply of the entire battery pack, thereby ensuring the safety of the battery pack. The confluence area mainly plays the role of current collection and conduction.

[0118] like Figure 9 As shown in the figure, the battery stack discharge results show that the battery stack discharges at a constant 4A for 2 minutes, pulses at 13A for 10 seconds, and then discharges at 4A for 2 minutes, achieving normal electrical performance. The 4A current is calculated based on the battery's rated operating current of 3.2A, distributed evenly to each cell for 0.29A. With six cells connected in parallel, the current is 1.74A. Based on a derating factor of less than 0.5, the discharge current is no less than 3.5A, so the actual test is performed at 4A. Similarly, the pulse discharge current is tested at 13A (12 ÷ 11 × 6 × 2).

[0119] From the discharge curve of the battery stack before short circuit, it can be seen that the current derating level reaches Level I after the battery stack is connected in parallel with the current-limiting nickel strip. The discharge curve of the battery stack is normal and can meet the use requirements.

[0120] After the discharge is completed, the battery stack is short-circuited and the open-circuit voltage of the battery stack is monitored during the short-circuit test. The open-circuit voltage change curve during the short-circuit test is shown below. Figure 10 .

[0121] like Figure 10 As shown, the battery stack's short-circuit instantaneous voltage dropped from 4.1158V to 0V in just 0.3s. After the test, the battery stack was inspected and found to have fused the six nickel strips at the positive electrode current limiter. The initial voltages of the six individual cells were all normal, around 4.11V.

[0122] The results of the battery stack short-circuit test show that the current-limiting nickel strip 2 current-limiting strip melts first during a short circuit, and the single battery is normal after melting.

[0123] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention to be approved.

Claims

1. A battery pack protection device, characterized in that: include: A battery holder (4) provided at both ends of a battery pack and supporting and fixing the battery pack, a printed circuit board (1) fixed to the battery holder (4), and a current-limiting nickel strip (2) fixed between the electrode of a single battery (3) and the printed circuit board (1); The current-limiting nickel strip (2) comprises: a single cell welding area connected to the electrode of the single cell (3), a busbar welding area (23) connected to the printed circuit board (1), and a current-limiting area (22) connecting the single cell welding area (21) and the busbar welding area (23); The printed circuit board (1) comprises a circuit for connecting each single battery (3) in the battery pack and an output electrode of the battery pack.

2. A battery pack protection device according to claim 1, characterized in that: The printed circuit board (1) substrate comprises an epoxy board and a confluence area (11) fixed to the epoxy board.

3. A battery pack protection device as claimed in claim 2, characterized in that: A copper-nickel-plated metal layer is provided on the surface of the epoxy board.

4. The battery pack protection device according to claim 1, wherein: The single cell welding area (21) comprises a welding piece adapted to the size of the single cell (3) and a long groove arranged in the middle of the welding piece.

5. The battery pack protection device according to claim 1, wherein: The structure of the flow limiting area (22) is strip-shaped.

6. The battery pack protection device according to claim 1, wherein: The series-parallel connection of the single cells all includes spot welding of mesh nickel strips.

7. The battery pack protection device according to claim 1, wherein: The thickness of the flow limiting area (22) is 0.1 to 0.2 mm.

8. The battery pack protection device according to claim 1, wherein: The width of the flow-limiting area (22) is 0.5 to 1 mm.

9. The battery pack protection device according to claim 1, wherein: The welding process of the current-limiting nickel strip (2) includes at least one of resistance welding and laser welding.

10. The battery pack protection device according to claim 1, wherein: The edges and middle of the battery support (4) are designed with snap fasteners (43) to fix the printed circuit board (1) on the end surface of the battery stack.

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