A compact nickel-hydrogen battery pack

Abstract

This utility model discloses a compact nickel-metal hydride battery pack, including battery cells and a connecting structure. Each battery cell has a housing, a core assembly embedded within the housing, and end caps. End caps are provided at both ends of the core assembly, and the core assembly and end caps are coaxially connected by connecting holes. The connecting structure has a connecting shaft and a locking assembly. The locking assembly has locking screws. The end caps of two connected battery cells are coaxially insulated and assembled. The connecting shaft passes through the connecting holes of two or more battery cells, and the end of the connecting shaft is threadedly connected to the locking screw for locking the coaxially assembled two or more battery cells. By connecting multiple battery cells in series via the connecting shaft, and by directly and seamlessly coaxially insulatedly assembling the end caps of two connected battery cells, the assembly gap between end caps is eliminated, reducing the axial dimension of the nickel-metal hydride battery pack by more than 15%, lowering the battery pack volume and transportation costs, simplifying the production process, and reducing material costs by more than 30%.

Description

Technical Field

[0001] This utility model relates to the field of battery manufacturing technology, and in particular to a compact nickel-metal hydride battery pack. Background Technology

[0002] Nickel-metal hydride (Ni-MH) batteries are alkaline secondary batteries that use metal hydride as the negative electrode and nickel hydroxide as the positive electrode. They are used in emergency power supplies and energy storage systems for energy-saving elevators, hybrid vehicles, and consumer electronics such as digital cameras.

[0003] Nickel-metal hydride (NiMH) battery packs consist of multiple battery cells connected in series via threaded connectors. Each battery cell typically comprises a housing, a core assembly, and an end cap. For example, Chinese invention patent CN112054269B, entitled "A Battery Cell and Battery Pack," includes a cylindrical body and a heat exchange tube. The cylindrical body has a first end cap and a second end cap at each end, defining a receiving space within which a battery cell assembly is located. The heat exchange tube passes through the first and second end caps, traversing the receiving space, and its outer wall contacts the battery cell assembly. This battery pack includes at least two battery cells connected in series via connectors. When connecting two battery cells using connectors, a relatively wide assembly gap is typically required between them. This gap allows for air intake or exhaust through the through-hole in the connector, achieving heat exchange.

[0004] However, the existing technology still has the following drawbacks:

[0005] (1) When two or more battery cells are assembled using a connecting kit, a large assembly gap is reserved at the end cap connection of the two battery cells, which will occupy a large space area when assembling the battery pack, thus making the entire battery pack larger, increasing transportation costs, and making assembly more complicated. Moreover, during production and processing, internal threads need to be machined on the end caps of the battery cells, and external threads and heat exchange through holes need to be machined on both ends of the connecting kit, which significantly increases material and production and processing costs and complicates the production and processing procedures.

[0006] (2) The end caps of the battery cells are only connected to each other by connecting kits through threads, resulting in insufficient overall structural strength and the problem that the two battery cells are prone to loosening due to opposite rotation directions. Utility Model Content

[0007] In order to overcome the shortcomings of the prior art, the purpose of this utility model is to provide a compact nickel-metal hydride battery pack.

[0008] The objective of this utility model is achieved through the following technical solution: a compact nickel-metal hydride battery pack, comprising battery cells and a connecting structure. The battery cell has a housing and a core assembly and end caps embedded in the housing. The end caps are provided at both ends of the core assembly, and the core assembly and end caps are coaxially connected through connecting holes. The connecting structure has a connecting shaft and a locking assembly. The locking assembly has a locking screw. The end caps of two connected battery cells are coaxially insulated and assembled. The connecting shaft is connected through the connecting holes of two or more battery cells, and the end of the connecting shaft is threadedly connected to the locking screw for locking two or more coaxially assembled battery cells.

[0009] Furthermore, the nickel-metal hydride battery pack also includes a positioning ring, the axial height of which is ≤ twice the inner cavity depth of the end cap. The positioning ring is disposed in the cover cavity formed by the end caps of the two battery cells, and the outer wall and end of the positioning ring are tightly fitted with the inner wall of the end cap for axial and radial positioning and assembly of the two battery cells.

[0010] Furthermore, the nickel-metal hydride battery pack also includes an insulating ring, which is placed between the end caps of the two battery cells for coaxial insulating assembly between the two end caps.

[0011] Furthermore, the locking assembly also has a connecting sleeve, which is fitted onto the locking screw, and the locking screw is interference-fitted with the connecting hole of the end cap through the connecting sleeve.

[0012] Furthermore, one end of the locking screw has an external thread end and the other end has a clamping head, both ends of the connecting shaft have internal threads, the external thread end of the locking screw is threadedly connected to the internal thread of the shaft, and the clamping head of the locking screw presses against the end of the end cap.

[0013] Furthermore, the locking assembly also has an end cap and an explosion-proof component. The end cap is located at the outer end of the locking screw and has several heat exchange cap holes that communicate with the air holes of the locking screw. The explosion-proof component is located inside the end cap and is used to connect or disconnect the air holes of the locking screw from the heat exchange cap holes.

[0014] Furthermore, the connecting shaft has an internal hollow structure, and the side wall of the connecting shaft has a heat exchange shaft hole that communicates with the interior, for inputting fluid into the connecting shaft and conducting heat transfer to the core assembly through the heat exchange shaft hole.

[0015] Furthermore, the battery cell also has a nickel cup, which is disposed between the end cap and the winding core assembly; the bottom of the nickel cup is also provided with a dividing cut for dividing the bottom of the cup into several welding parts, and each welding part is provided with a cup body protrusion, which is welded to the tab of the winding core assembly.

[0016] Furthermore, a central hole is provided in the middle of the bottom of the nickel cup, the inner end of the dividing cut is connected to the central hole, the outer end extends toward the edge of the nickel cup and is not connected to the edge of the nickel cup, and several dividing cuts are arranged in a ring array around the central hole.

[0017] Furthermore, the nickel cup has several cup body edge teeth spaced apart along its edge. The cup body edge teeth bend 90° upwards from the bottom of the nickel cup along the bend. The cup body edge teeth are welded to the end cap.

[0018] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0019] (1) Compared with the traditional implementation method of connecting two battery cells in series using a connecting kit, the embodiments of this application connect multiple battery cells end to end in series by connecting shaft, and the end caps of two connected battery cells are directly and seamlessly coaxially insulatedly assembled, eliminating the assembly gap between the end caps, so that the axial dimension of the nickel-metal hydride battery pack is reduced by more than 15%, reducing the battery pack volume and transportation cost; eliminating the need for machining the internal threads of the end caps and the external threads of the connecting sleeves, simplifying the production process, reducing material costs by more than 30%, and reducing the amount of locking screws used by more than half, simplifying the locking structure of the nickel-metal hydride battery pack.

[0020] (2) By setting a positioning ring, the nickel-metal hydride battery pack uses the interference fit and end face abutment assembly of the positioning ring and the end cap to position the end caps of the two battery cells connected in series. This is used to radially constrain the displacement of the end caps of the two battery cells and prevent the battery cells from being misaligned during assembly; to axially share the locking stress and reduce the risk of deformation of the connecting shaft; to improve the vibration resistance of the nickel-metal hydride battery pack and extend its service life; and to reduce the risk of loosening in opposite directions caused by the traditional battery cells' end caps being connected to each other by connecting kits through threaded connections, thereby improving the overall structural strength and assembly stability. Attached Figure Description

[0021] Figure 1 This is a perspective view of the novel nickel-metal hydride battery in a preferred embodiment of the present invention.

[0022] Figure 2 This is an exploded view of the structure of the novel nickel-metal hydride battery in a preferred embodiment of the present invention;

[0023] Figure 3 This is a top view of the novel nickel-metal hydride battery in a preferred embodiment of the present invention;

[0024] Figure 4 for Figure 3 A three-dimensional sectional view after being cut along the AA direction;

[0025] Figure 5 for Figure 4 Enlarged view of point B in the middle;

[0026] Figure 6 for Figure 4 Enlarged view of point C in the middle;

[0027] Figure 7 This is a three-dimensional schematic diagram showing a partial cross-section and structural decomposition of the end cap, nickel cup, and other components of the novel nickel-metal hydride battery in a preferred embodiment of this utility model.

[0028] In the picture:

[0029] 10. Battery cell; 101. Housing; 102. Core assembly; 103. End cap; 1031. Cover chamber; 104. Connection hole; 105. Nickel cup; 1051. Welded part; 10511. Cup body protrusion; 1052. Dividing notch; 1053. Center hole; 1054. Cup body edge teeth; 106. Insulating positioning component;

[0030] 20. Connection structure; 201. Connecting shaft; 2011. Internal thread of the shaft; 2012. Heat exchange shaft hole; 202. Locking assembly; 2021. Locking screw; 20211. External thread end; 20212. Pressing head; 20213. Air hole; 2022. End cap; 20221. Heat exchange cap hole; 2023. Explosion-proof component; 203. Connecting sleeve;

[0031] 30. Positioning circle;

[0032] 40. Insulating ring. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0034] like Figure 1-7 As shown, a compact nickel-metal hydride battery pack is applicable to fields such as emergency power supplies, energy storage systems for energy-saving elevators, hybrid vehicles, and consumer electronics such as digital cameras. This compact nickel-metal hydride battery pack includes a single battery cell 10 and a connecting structure 20. The single battery cell 10 includes a housing 101, a winding assembly 102, and end caps 103 at both ends. The housing 101 is generally cylindrical.

[0035] The core assembly 102 is coaxially disposed within the housing 101. The core assembly 102 has several positive and negative tabs. The end cap 103 has a through hole in its center, and the core assembly 102 has a through connection hole 104. When the end caps 103 are installed at both ends of the core assembly 102, the housing 101, the core assembly 102, and the end caps 103 are arranged coaxially. An insulating positioning component 106 is also provided between the outer periphery of the end cap 103 and the inner wall of the housing 101. The insulating positioning component 106 is a ring-shaped plastic part. The cross-section of the side wall of the insulating positioning component 106 is approximately L-shaped. The inner side of the insulating positioning component 106 has a groove that engages with the groove on the outer wall of the end cap 103. The outer side of the insulating positioning component 106 abuts against the inner wall of the housing 101. Thus, the insulating positioning component 106 positions and fixes the end cap 103 and the housing 101 to each other, ensuring precise alignment, preventing misalignment during assembly, and improving the overall assembly stability of the nickel-metal hydride battery.

[0036] The connecting structure 20 includes a connecting shaft 201 and a locking assembly 202. When assembling a nickel-metal hydride battery pack, the end caps 103 of two connected battery cells 10 are assembled coaxially with no gaps by using an insulating ring 40. The insulating ring 40 can be made of insulating materials such as rubber. The connecting shaft 201 passes sequentially through the connecting holes 104 of the core assembly 102 and the end caps 103 of multiple battery cells 10 connected end to end. One end of the locking screw 2021 is an external thread end 20211, and the other end is a larger diameter clamping head 20212. Both ends of the connecting shaft 201 are machined with internal threads. Therefore, the external thread end 20211 of the locking screw 2021 is screwed into the internal thread 2011 of the connecting shaft 201, and the clamping head 20212 directly clamps the outer end of the end cap 103, thereby axially locking two or more coaxially assembled battery cells 10. Furthermore, the locking screw 2021 is equipped with a larger diameter clamping head 20212, which increases the force-bearing area and reduces the surface pressure of the end cap 103 by 50%.

[0037] Therefore, compared with the traditional implementation method of connecting two battery cells 10 in series using connecting sleeves 203, the embodiment of this application connects multiple battery cells 10 connected end to end in series via connecting shaft 201, and the end caps 103 of two connected battery cells 10 are directly and seamlessly coaxially insulatedly assembled, eliminating the assembly gap between end caps 103, thereby reducing the axial dimension of the nickel-metal hydride battery pack by more than 15%, reducing the battery pack volume and transportation costs; eliminating the need for machining the internal threads of the end caps 103 and the external threads of the connecting sleeves 203, simplifying the production process, reducing material costs by more than 30%, and reducing the use of locking screws 2021 by more than half, simplifying the locking structure of the nickel-metal hydride battery pack.

[0038] The nickel-metal hydride battery pack in this embodiment of the application also includes a positioning ring 30, the outer diameter of which is equal to the inner diameter of the end cap 103. Figure 5As shown, the axial height h1 of the positioning ring 30 is less than or equal to twice the inner cavity depth h2 of the end cap 103 (preferably 0.8-1 times). During assembly, the positioning ring 30 is first installed on the end cap 103 of one of the battery cells 10, and then the end cap 103 of the other battery cell 10 is assembled with the positioning ring 30, thereby embedding the positioning ring 30 into the cover cavity 1031 formed by the contact assembly of the two end caps 103. Moreover, the outer wall of the positioning ring 30 is interference-fitted with the inner wall of the end cap 103, and the end face of the positioning ring 30 abuts against the bottom surface of the cavity.

[0039] Therefore, the nickel-metal hydride battery pack of this application embodiment uses a positioning ring 30. Through the interference fit and end face abutment assembly of the positioning ring 30 and the end cap 103, the end caps 103 of the two battery cells 10 connected in series are positioned and assembled. This is used to radially constrain the displacement of the end caps 103 of the two battery cells 10, preventing misalignment of the battery cells 10; axially share the locking stress, reducing the risk of deformation of the connecting shaft 201; improve the vibration resistance of the nickel-metal hydride battery pack, extend its service life; and reduce the risk of loosening in opposite directions caused by the traditional connection of the end caps 103 of the battery cells 10 through the threaded connection of the connecting sleeve 203, thereby improving the overall structural strength and assembly stability.

[0040] The locking assembly 202 also includes a connecting sleeve 203, which is fitted onto the shank of the locking screw 2021 and located at one end of the clamping head 20212. The outer diameter of the connecting sleeve 203 is 0.05-0.1 mm larger than the diameter of the connecting hole 104 of the end cover 103. During locking, the connecting sleeve 203 is pressed into the connecting hole 104 of the end cover 103 to form an interference fit. The clamping head 20212 of the locking screw 2021 presses against the end face of the connecting sleeve 203. The locking screw 2021 disperses the stress on the end cover 103 through the interference fit between the connecting sleeve 203 and the end cover 103, preventing the end cover 103 from cracking and improving assembly stability. In addition, anti-crack openings are provided at both ends of the connecting shaft 201. When the locking screw 2021 is threadedly connected to the connecting shaft 201, the anti-crack openings prevent the ends of the connecting shaft 201 from cracking due to expansion.

[0041] The locking assembly 202 also includes an end cap 2022 and an explosion-proof component 2023. The end cap 2022 is installed on the outer end of the locking screw 2021, and multiple heat exchange cover holes 20221 are formed on the end cap 2022. The explosion-proof component 2023 is installed inside the end cap 2022, and the explosion-proof component 2023 is made of shape memory alloy explosion-proof sheet. Under normal conditions, the explosion-proof component 2023 seals the vent 20213 of the locking screw 2021. When the battery cell 10 is overcharged or at high temperature, the electrolyte decomposes to produce hydrogen gas, causing the internal pressure to rise. This causes the explosion-proof component 2023 to deform and open the vent 20213 of the locking screw 2021, which then connects to the heat exchange cover hole 20221 of the top cover 2022, allowing for directional venting and pressure relief. The explosion-proof response time is <3ms, preventing the casing 101 from bursting. When the pressure drops, the explosion-proof component 2023 resets and re-closes the vent 20213 of the locking screw 2021, maintaining the subsequent sealing of the battery cell 10.

[0042] The connecting shaft 201 is designed as a hollow tube, with a radially communicating heat exchange shaft hole 2012 on its side wall. Cooling fluid enters the connecting shaft 201 sequentially from the heat exchange cover hole 20221 of the end cap 2022 and the vent hole 20213 of the locking screw 2021, and is then sprayed through the heat exchange shaft hole 2012 to the center of the core assembly 102, forming an axial heat dissipation path. This directly cools the hot spot at the center of the core, controlling the temperature difference within ±2℃; compared to traditional liquid cooling methods, the cooling efficiency is significantly improved.

[0043] The battery cell 10 also includes a nickel cup 105, which is installed on the end of the winding assembly 102, and then an end cap 103 is installed on the nickel cup 105, such that the nickel cup 105 is located between the end cap 103 and the winding assembly 102.

[0044] The bottom of the nickel cup 105 is divided into multiple independent welding portions 1051 by a dividing cut 1052. Each welding portion 1051 has several cup body protrusions 10511 integrally stamped on it, and these protrusions are either three-dimensional cones or squares. When the nickel cup 105 is mounted on the core assembly 102, these cup body protrusions 10511 on the welding portions 1051 can be inserted between the layered tabs of the core assembly 102. Then, spot welding can be performed from the dividing cut 1052 of the nickel cup 105 to fix the cup body protrusions 10511 to the tabs of the core assembly 102 by spot welding or laser welding.

[0045] During spot welding, the positive and negative welding needles respectively contact two adjacent welding parts 1051. Therefore, the current from the positive and negative welding needles can flow along the shortest path along the cup protrusion 10511 of the two adjacent welding parts 1051. Previously, without the nickel cup 105, the current between the positive and negative welding needles would flow radially from the end cap 103, which would consume a large current and could not meet the spot welding current requirements, thus affecting the welding effect.

[0046] Therefore, by setting a nickel cup 105 between the core assembly 102 and the end cap 103, and forming multiple welding parts 1051 by opening a dividing cut 1052 on the nickel cup 105, each welding part 1051 is provided with a cup body protrusion 10511. During installation, the cup body protrusion 10511 is inserted between the tabs of the core assembly 102, increasing the contact area between the nickel cup 105 and the tabs, and increasing the welding contact area by more than 30%. The current of welding the positive and negative electrodes can flow along the shorter path of the cup body protrusion 10511 of two adjacent welding parts 1051, that is, shortening the current path of welding the positive and negative electrodes. Compared with the previous implementation method where the current flows radially from the end cap 103, the spot welding internal resistance is reduced by 15%-20%. Sufficient current is provided to ensure the welding penetration and fusion effect, improve the welding stability of the nickel cup 105 and the core assembly 102, enhance conductivity, ensure the charging and discharging effect of the nickel-metal hydride battery, improve safety, and extend service life.

[0047] In addition, the nickel cup 105, as an intermediate connector between the end cap 103 and the core assembly 102, can be welded to the tabs of the core assembly 102 first and then to the end cap 103. Finally, the whole assembly is installed into the housing 101. The large welding area of ​​the nickel cup 105 with the core assembly 102 and the end cap 103 improves the overall welding structure strength and avoids the risk of weld breakage caused by the end cap 103 being directly welded to the core assembly 102 in the traditional process. The pre-welded nickel cup 105 and the modular assembly process increase production efficiency by 25% and reduce the defect rate by 10%.

[0048] A central hole 1053 is provided at the center of the bottom of the nickel cup 105. The inner end of the dividing cut 1052 communicates with the central hole 1053, and the outer end extends toward the edge of the nickel cup 105 but does not communicate with it. That is, the outer end of the dividing cut 1052 terminates on the inner side of the edge of the nickel cup 105, maintaining a certain distance from the edge of the nickel cup 105 to ensure the structural integrity of the bottom edge. Therefore, the continuous area of ​​the bottom edge is preserved to prevent the dividing cut 1052 from causing a decrease in the overall rigidity of the nickel cup 105; the length of the cut is limited to prevent molten metal from overflowing and contaminating the shell 101 or insulating parts during welding.

[0049] By designing the segmented cuts 1052 on the nickel cup 105, the segmented cuts 1052 are arranged in a ring array around the central hole 1053, forming a radial structure. The central hole 1053 and the radial cut design of the nickel cup 105 reduce spot welding current loss by 40% and increase the weld penetration rate to over 99.5%. The radial distribution of the segmented cuts 1052 shortens the current path from the nickel cup 105 to the electrode, optimizes the current path, and reduces current loss; and the ring array of segmented cuts 1052 ensures uniform distribution of welding heat, avoiding local overheating or incomplete penetration.

[0050] The nickel cup 105 has several cup body edge teeth 1054 along its edge. The cup body edge teeth 1054 are bent upward at 90° along the bending part. After bending, the upward bending part of the cup body edge teeth 1054 can fit with the outer peripheral wall of the end cap 103, thereby laser welding the body edge teeth with the outer peripheral wall of the end cap 103 to fix them.

[0051] Therefore, by setting cup body edge teeth 1054 around the four periphery of the nickel cup 105 and welding it to the end cap 103, instead of the traditional direct welding method between the bottom surface of the end cap 103 and the electrode lug, the welding contact surface is further expanded, and the connection reliability is improved. At the same time, the nickel cup 105 is pre-fixed to the end cap 103 through the cup body edge teeth 1054, further avoiding weld point breakage caused by assembly after spot welding. During assembly, the bent part of the nickel cup 105 serves as a positioning reference, ensuring accurate alignment between the nickel cup 105 and the end cap 103, achieving precise positioning assembly; the spacing distribution of the cup body edge teeth 1054 improves the vibration resistance of the end cap 103 and the nickel cup 105 joint, enhances shear resistance, and further improves the overall welded structure strength.

[0052] In this embodiment of the application, the overall assembly process of the nickel-metal hydride battery pack is as follows:

[0053] Step 1: Assembly of 10 battery cells

[0054] The winding core assembly 102 is installed into the housing 101 with the tabs at both ends facing the opening. The nickel cup 105 is installed into both ends of the winding core assembly 102 and its cup body protrusion 10511 is embedded in the tabs at both ends of the winding core assembly 102. Welding is performed on the welding part 1051 of the nickel cup 105 so that the cup body protrusion 10511 is welded to the tab. The end cap 103 is pressed into the housing 101 and placed on the nickel cup 105. The cup body edge teeth 1054 are bent to the outer side wall of the end cap 103 and welded to fix it.

[0055] Step 2: Battery pack assembly

[0056] The positioning ring 30 is embedded in the end cap 103 of one of the battery cells 10. An insulating ring 40 is attached to the end face of the end cap 103. Then, the end cap 103 of the other battery cell 10 is aligned with the positioning ring 30 and assembled until the end faces of the two end caps 103 are pressed against the insulating ring 40, so that the positioning ring 30 is pressed into the cover cavity 1031 formed after the two end caps 103 are assembled. The two battery cells 10 are axially and radially positioned and assembled by the positioning ring 30.

[0057] The connecting shaft 201 passes sequentially through the connecting holes 104 of the core assembly 102 and end cap 103 of all individual cells. After the locking screw 2021 is fitted onto the connecting sleeve 203, it is screwed sequentially into the connecting hole 104 of the end cap 103. The external thread end 20211 of the locking screw 2021 is threaded to the internal thread of the connecting shaft 201. The clamping head 20212 of the locking screw 2021 clamps the outside of the end cap 103, and the connecting shaft 201 bears the axial mechanical load. The outer end of the locking screw 2021 is correspondingly installed with the explosion-proof part 2023 and the end cap 2022 for locking two or more coaxially assembled battery cells 10.

[0058] Step 3: Thermal Management and Safety Protection

[0059] Coolant is injected from one end of the end cap 103 and the connecting shaft 201, sprayed towards the center of the core through the heat exchange shaft hole 2012 of the connecting shaft 201, and flows out from the other end; when there is an abnormal temperature rise, the explosion-proof part 2023 deforms and opens the air hole 20213 of the locking screw 2021, and the high temperature gas is discharged through the air hole 20213 and the heat exchange cover hole 20221 of the end cap 2022.

[0060] Step 4: Electrical connection and charging / discharging

[0061] Current path: core tab → welding part 1051 of nickel cup 105 → positive and negative electrodes of adjacent battery cell 10 → external circuit.

[0062] The above embodiments are merely preferred embodiments of this utility model and should not be construed as limiting the scope of protection of this utility model. Any non-substantial changes and substitutions made by those skilled in the art based on this utility model shall fall within the scope of protection claimed by this utility model.

Claims

1. A compact nickel-metal hydride battery pack, characterized in that, The device includes a battery cell and a connecting structure. The battery cell has a housing and a core assembly and end caps embedded in the housing. The end caps are provided at both ends of the core assembly, and the core assembly and end caps are coaxially connected through connecting holes. The connecting structure has a connecting shaft and a locking assembly. The locking assembly has a locking screw. The end caps of two connected battery cells are coaxially insulated and assembled. The connecting shaft is connected through the connecting holes of two or more battery cells, and the end of the connecting shaft is threadedly connected to the locking screw for locking two or more coaxially assembled battery cells.

2. The compact nickel-metal hydride battery pack as described in claim 1, characterized in that, The nickel-metal hydride battery pack also includes a positioning ring. The axial height of the positioning ring is ≤ twice the inner cavity depth of the end cap. The positioning ring is disposed in the cover cavity formed by the end caps of the two battery cells, and the outer wall and end of the positioning ring are tightly fitted with the inner wall of the end cap for axial and radial positioning and assembly of the two battery cells.

3. The compact nickel-metal hydride battery pack as described in claim 1, characterized in that, The nickel-metal hydride battery pack also includes an insulating ring, which is placed between the end caps of two battery cells for coaxial insulating assembly between the two end caps.

4. The compact nickel-metal hydride battery pack as described in claim 1, characterized in that, The locking assembly also has a connecting sleeve, which is fitted onto the locking screw, and the locking screw is interference-fitted with the connecting hole of the end cap through the connecting sleeve.

5. The compact nickel-metal hydride battery pack as described in claim 1, characterized in that, The locking screw has an external thread end at one end and a clamping head at the other end. The connecting shaft has internal threads at both ends. The external thread end of the locking screw is threadedly connected to the internal thread of the shaft. The clamping head of the locking screw presses against the end of the end cap.

6. The compact nickel-metal hydride battery pack as described in claim 1, characterized in that, The locking assembly also has an end cap and an explosion-proof component. The end cap is located at the outer end of the locking screw. The end cap has several heat exchange cover holes that are connected to the air holes of the locking screw. The explosion-proof component is located inside the end cap and is used to connect or disconnect the air holes of the locking screw from the heat exchange cover holes.

7. The compact nickel-metal hydride battery pack according to any one of claims 1-6, characterized in that, The connecting shaft has an internal hollow structure, and the side wall of the connecting shaft has a heat exchange shaft hole that communicates with the interior, for inputting fluid into the connecting shaft and conducting heat transfer to the core assembly through the heat exchange shaft hole.

8. The compact nickel-metal hydride battery pack according to any one of claims 1-6, characterized in that, The battery cell also has a nickel cup, which is located between the end cap and the winding core assembly. The bottom of the nickel cup is also provided with a dividing cut for dividing the bottom of the cup into several welding parts. Each welding part is provided with a cup body protrusion, which is welded to the tab of the winding core assembly.

9. The compact nickel-metal hydride battery pack as described in claim 8, characterized in that, The nickel cup has a central hole in the bottom center. The inner end of the dividing cut is connected to the central hole, and the outer end extends toward the edge of the nickel cup but is not connected to the edge of the nickel cup. Several dividing cuts are arranged in a ring array around the central hole.

10. The compact nickel-metal hydride battery pack as described in claim 8, characterized in that, The nickel cup has several edge teeth spaced apart along its edge. The edge teeth are bent at 90° from the bottom of the nickel cup upwards along the bend. The edge teeth are welded to the end cap.

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