DESC:
Field of Invention
The present disclosure relates to lead-acid battery technologies, specifically to punched grid design and manufacturing methods for enhancing structural rigidity and reducing grid growth in lead-acid batteries.

Background
Electrochemical energy storage in batteries is highly attractive due to its compactness, ease of deployment, cost-effectiveness, and ability to provide an almost instantaneous response to both input and output demands. Among the various battery chemistries available, lead-acid batteries stand out as a reliable and economical solution, adaptable for a wide range of energy storage applications. In these batteries, grids are stacked together as positive and negative plates, interleaved with a porous, electrically insulating separator. The plate stack is housed within a molded polymer case, which contains the cell components and electrolyte, along with terminals, a lid, and venting arrangements. Positive plates in lead-acid batteries can be either flat pasted or tubular, while negative plates are consistently of the flat-pasted type. Additionally, there are spiral wound plate types and bipolar designs, though these are typically limited to smaller capacities. Cells may also be categorized as either flooded or valve-regulated lead-acid (VRLA) types.

The prior art in grid design includes several notable works:
Geoffrey J. May, Alistair Davidson, and Boris Monahov, in their review titled "Lead batteries for utility energy storage" published in the Journal of Energy Storage, volume 15, discuss the critical role of energy storage in stabilizing electricity networks and the variety of battery chemistries available. The paper highlights that lead-acid cells are constructed from lead alloy grids, which provide mechanical support to the positive and negative active materials and function as current collectors. For pasted plates, grids can be manufactured by casting, slitting and expanding sheets of lead alloy, or by punching sheets of lead alloy. The lead alloy may contain antimony in varying quantities, or be alloyed with calcium, tin, and other elements, or it may be pure lead with minor alloying additions, often including tin. Alloys with antimony are typically used for positive grids in flooded cells designed for deep cycle applications, while alloys with calcium and tin, as well as pure lead, are used for positive grids in VRLA cells. Different alloys with lower antimony levels may be employed for negative grids in deep cycle service. For certain types of flooded cells, alloys with calcium and lower levels of tin are used for negative grids, and these alloys are also used for VRLA cells. The active materials are applied to the grids in the form of a porous paste formulated from lead oxide and sulfuric acid. During paste mixing, basic lead sulfates develop, forming a robust, interlocking structure that is well bonded to the grids. The pasted plates are then processed in hot, humid conditions (curing) to ensure the paste particles become strongly bonded to each other and the grid surfaces. The basic lead sulfates are subsequently converted to lead dioxide and lead through an electrochemical formation process. The positive active material may contain minor additives or strengthening fibers, while the negative active material includes specific additives such as barium sulfate, lignosulfonates, and carbon black as expanders, along with fibers. These additives maintain the microporous and conductive structure of the negative active mass in service, improving low-temperature performance and cycle life. However, this article does not teach or suggest a new punched grid design with a specific mass distribution within the grid wires and frames.

US5989749A discloses a stamped grid for a lead-acid battery, featuring a grid pattern optimized for electrical performance. The stamped grid includes an electrically conductive grid body with opposed top and bottom frame elements, opposed first and second side frame elements, and a plurality of interconnecting grid wire elements forming a grid pattern. The grid wire elements include vertical wire elements electrically connected to both top and bottom frame elements, vertical wire elements connected to the top frame element and one of either the first or second side frame elements, and a plurality of cross grid elements that interconnect the vertical wire elements. Each vertical grid element electrically connected to the top frame element and one of either the first or second side frame elements includes a plurality of cross frame elements connected thereto at a substantially 90° angle. The vertical grid elements and the cross frame elements define open areas for supporting electrochemical paste, where most of the open areas are within two percent of being the same size.

KR102122987B1 describes a perforated substrate for a lead-acid battery designed to suppress grid growth. Specifically, the top side vertical wire is formed between any one vertical wire and the other vertical wire formed immediately below, ensuring that the top side vertical wire and the vertical wire are not positioned in a straight line. This configuration inhibits grid growth. Additionally, by dispersing the growth of the horizontal wire, the design is expected to improve the life of the lead-acid battery. However, the vertical wires are not continuous, resulting in grids with lower cold cranking amps (CCA) compared to grids with continuous vertical wires.

Despite these advancements, the prior art does not adequately address grid growth in punched grids made from rolled lead strips. Therefore, there is a need for punched grids that effectively arrest grid growth.

The present invention offers a specific punched grid arrangement with structural rigidity and a differential distribution of lead mass, reducing the propensity for growth and enhancing the service life of the product.

Objects of the invention
An object of the present invention is to address and overcome the challenges associated with grid growth in lead-acid battery electrodes, particularly in punched grids made from rolled lead strips.

Another object of the invention is to enhance the structural rigidity of the grid, ensuring that corrosion occurs in designated areas to effectively arrest grid growth.

A further object of the invention is to optimize the differential distribution of lead mass within the grid, thereby reducing the propensity for grid growth and extending the service life of the battery.

Yet another object of the invention is to improve the electrical performance and mechanical stability of the grid, contributing to the overall efficiency and longevity of lead-acid batteries.

Another object of the present invention is to provide a punched lead grid for a lead-acid battery electrode, comprising:
a grid body formed from a rolled lead strip; a plurality of grid wires and
frame elements arranged to define multiple quadrants;
wherein each quadrant has a differential distribution of lead mass.

Yet another object of the invention is to provide a method of manufacturing a punched lead grid for a lead-acid battery electrode, comprising:
providing a lead strip;
reducing the thickness of the lead strip through a rolling process;
punching the rolled lead strip to form a grid with a plurality of grid wires and frame elements arranged to define multiple quadrants;
configuring the grid with a differential distribution of lead mass across the quadrants to enhance structural integrity and reduce grid growth.

Summary
The present invention provides a punched lead grid for a lead-acid battery electrode, comprising a grid body formed from a rolled lead strip; a plurality of grid wires and frame elements arranged to define multiple quadrants; wherein each quadrant has a differential distribution of lead mass. In another embodiment, the disclosure includes a punched lead grid wherein the first quadrant, positioned closest to the grid lug, comprises between 32% and 40% by weight of the total lead mass of the grid; the second quadrant comprises between 20% and 25% by weight of the total lead mass of the grid; the third quadrant, positioned at the greatest distance from the grid lug, comprises between 12% and 18% by weight of the total lead mass of the grid; and the fourth quadrant comprises between 25% and 28% by weight of the total lead mass of the grid. In a further embodiment, the disclosure includes a punched lead grid wherein the differential distribution of lead mass is configured to impart structural rigidity and to establish differential current densities that facilitate preferential corrosion in selected quadrants and thereby arrest grid growth and enhance service life of the battery.

The present invention further discloses a method of manufacturing a punched lead grid for a lead-acid battery electrode, comprising providing a lead strip; reducing the thickness of the lead strip through a rolling process; punching the rolled lead strip to form a grid with a plurality of grid wires and frame elements arranged to define multiple quadrants; configuring the grid with a differential distribution of lead mass across the quadrants to enhance structural integrity and reduce grid growth. In a further embodiment, the disclosure includes a method wherein the rolling process reduces the thickness of the lead strip to between 0.7 mm and 1.2 mm, optimizing the strip for subsequent punching; the punching process is performed using a progressive punch tool, ensuring precision and consistency in the formation of the grid wires and frame elements; and the differential distribution of lead mass is achieved by varying the width and thickness of the grid wires in each quadrant, tailored to enhance structural integrity and reduce grid growth. These and other features will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims.

Brief description of drawings
FIG. 1 is a schematic diagram illustrating the punched grid design with differential mass distribution across four quadrants.
FIG. 2 illustrates a comparative analysis of grid deformation in different punched grid designs for lead-acid batteries.
FIG. 3 is a comparative view illustrating the condition of regular punch grid and punched grids of the present invention before and after a corrosion test.

Detailed description
The present invention discloses a new punched grid arrangement having a particular mass distribution within the grid wires and frames, with weight distribution within the wires at the four quadrants with reference to the grid tab/lug. This arrangement imparts the required structural strength, ensuring that grid growth is delayed or arrested. The punched grid arrangement arrests growth due to optimal structural strength and electrical current distribution. Higher structural strength reduces the possibility of growth, while lower electrical current distribution decreases the rate of corrosion. Differential mass distribution leads to varying current densities, resulting in preferential corrosion that arrests growth and imparts strength to areas as needed to improve the product's life.

In one embodiment, the punched lead grid for a lead-acid battery electrode is constructed from a rolled lead strip with a thickness reduced to between 0.7 mm and 1.2 mm, optimizing the strip for the punching process. The grid body is designed with a plurality of grid wires and frame elements that define four distinct quadrants, each with a differential distribution of lead mass. The first quadrant, positioned closest to the grid lug, comprises between 32% and 40% by weight of the total lead mass, providing structural support and minimizing corrosion due to the lower current density. The second quadrant, comprising between 20% and 25% by weight, is structurally reinforced to support the first quadrant. The third quadrant, located at the greatest distance from the lug, contains between 12% and 18% by weight, designed to corrode preferentially due to the higher current density, thereby arresting grid growth. The fourth quadrant, with a mass distribution of 25% to 28%, acts as a secondary support, ensuring the grid's structural integrity and enhancing the battery's service life.

The weight distribution (gm) of lead mass across the grid is shown in Table 1.

4th Quadrant
25%-28%
1st Quadrant
32-40%

3rd Quadrant
12%-18%
2nd Quadrant
20-25%

Table 1

The weight distribution values have been optimized considering finite element analysis and novel mass distribution across 4 quadrants so that the current carrying electrode continues to provide cranking current when some quadrants have to preferentially corrode off, thereby enhancing service life.

The present invention can be better understood with reference to the accompanying Figure 1.

FIG. 1 shows a schematic diagram illustrating the punched grid design with differential mass distribution across four quadrants. This design plays a significant role in the described technology, as the strategic allocation of lead mass optimizes the grid's structural integrity and performance in a lead-acid battery. The first quadrant, positioned close to the lug 100, is designed to have the maximum mass. This configuration ensures that the first quadrant experiences reduced current density, which results in slower corrosion rates. As a result, this enhances the overall life of the battery by maintaining the structural integrity of the grid in the area adjacent to the lug 100, which is important for electrical connectivity. The fourth quadrant follows the first in terms of mass distribution. This quadrant functions as a secondary support structure, providing additional strength to the grid. The mass distribution in this quadrant plays a significant role in maintaining the grid's stability and preventing growth towards the lug, which could otherwise compromise the battery's performance. The second quadrant is designed to be strong enough to support the first quadrant. Although the second quadrant has less mass than the first and fourth quadrants, the structural design ensures that the second quadrant can effectively support the load and maintain the grid's integrity. The mass distribution of the second quadrant is optimized to balance the need for support with the overall weight constraints of the grid. The third quadrant, positioned at the greatest distance from the lug, has the minimum mass. This design choice results in a significant current density in this quadrant, leading to preferential corrosion. The intentional design of this quadrant to corrode first helps arrest grid growth by preventing the expansion of the grid in the distant side of the lug. This strategic corrosion pattern ensures that the grid maintains its structural integrity and continues to function effectively throughout the battery's service life. Overall, the differential mass distribution across the four quadrants represents a significant advancement in the design, providing a balance between structural strength and controlled corrosion to enhance the battery's longevity and performance.

According to another embodiment, the present invention provides a horizontal wire layout in which the horizontal wires are made discontinuous touching the side vertical frames. Alternatively, the horizontal wires are taken up to lug side horizontal frames. Both layouts (or arrangements) show identical deformation. The present invention also provides a certain angle of the horizontal wires which result in maximum reduction of average deformation. The angle and the discontinuity of the horizontal wires both contribute in avoiding growth on the width side of the grid. The angle of horizontal wires with respect to vertical wires can be within the range of 70-90 degree.

It is important to understand the significance of grid deformation in lead-acid battery performance. Grid deformation can adversely affect the structural integrity and electrical efficiency of the battery, leading to reduced service life and reliability. The present invention addresses these challenges by introducing innovative grid designs that optimize the distribution of stress and current density across the grid. By employing different wire layouts, including discontinuous horizontal wires and angular configurations, the invention aims to minimize deformation and enhance the grid's ability to withstand mechanical and thermal stresses. This approach not only improves the battery's durability but also ensures consistent performance over extended periods. FIG. 2 visually represents the impact of these design choices on grid deformation, providing valuable insights into the effectiveness of the proposed solutions.

FIG. 2 depicts the maximum/minimum and average deformation of the punched grid design, highlighting the structural strength of the grid as studied through thermal analysis. The figure presents three different configurations of the NST1.0 grid design, each demonstrating varying levels of deformation under static structural conditions.

The first configuration, labeled "NST1.0 With Horizontal wire," illustrates a grid design where horizontal wires are incorporated. In this layout, the horizontal wires are made discontinuous, touching the side vertical frames. This design results in a maximum deformation of 6.26 mm and an average deformation of 2.12 mm. The discontinuous horizontal wire layout contributes to the structural integrity by distributing stress across the grid, reducing deformation by 2% and 16% respectively compared to previous designs.

The second configuration, "New NST1.0 with Angular Horizontal Wire," introduces angular horizontal wires into the grid design. This modification leads to a reduced maximum deformation of 5.84 mm and an average deformation of 2.1 mm. The angular orientation of the wires enhances the grid's ability to withstand stress, achieving a 9% reduction in maximum deformation and a 16% reduction in average deformation. This design optimizes the grid's structural strength by strategically altering the wire angles to better distribute forces.

The third configuration, "NST1.0 With Horizontal & Angular wire," combines both horizontal and angular wire elements. In this layout, the horizontal wires are alternatively taken up to the lug side horizontal frames. This iteration achieves a maximum deformation of 5.96 mm and an average deformation of 1.94 mm, representing a 6.6% and 23% reduction respectively. The combination of wire orientations provides a synergistic effect, further minimizing deformation and enhancing the grid's structural resilience.

Both the discontinuous horizontal wire layout and the alternative layout where horizontal wires extend to the lug side frames show identical deformation, demonstrating the versatility and effectiveness of the design in maintaining structural integrity.

From the analysis presented in FIG. 2, it is evident that the present invention incorporates a specific angular orientation of the horizontal wires, which significantly contributes to the maximum reduction of average deformation. This strategic angular configuration, combined with the discontinuity of the horizontal wires, plays a crucial role in mitigating grid growth along the width side. By optimizing the wire angles, the design effectively distributes mechanical stress and current density, thereby enhancing the grid's structural integrity and reducing the likelihood of deformation. This approach not only prevents undesirable expansion but also ensures the grid maintains its intended shape and functionality, ultimately improving the battery's performance and longevity.

Apart from grid deformation, it is also essential to understand the importance of corrosion resistance in lead-acid battery grids. Corrosion is a major factor that affects the longevity and performance of battery grids, often leading to structural degradation and reduced electrical efficiency. The present invention addresses these challenges by introducing a punched grid design with a differential mass distribution, strategically engineered to enhance corrosion resistance and structural integrity. This innovative design aims to optimize current density and manage corrosion patterns, ensuring that the grid maintains its functionality even under severe conditions, such as overcharge scenarios. FIG. 3 provides a visual comparison of different grid designs subjected to a 3V overcharge test, highlighting the effectiveness of the present invention in mitigating corrosion and preserving grid structure.

FIG. 3 shows a comparative view of the condition of different punched grids before and after a 3V overcharge test, also known as a corrosion test. The figure illustrates three types of grids: a regular punched grid, a punched grid with distributed mass according to the present design - The regular punched grid, depicted on the left, demonstrates significant structural degradation after the corrosion test. Before the test, the grid appears intact with a uniform distribution of grid wires. However, after the test, the grid shows extensive corrosion and disintegration, indicating an inability to withstand the overcharge conditions. This highlights the limitations of traditional grid designs in maintaining structural integrity under corrosive environments. The punched grid with distributed mass, shown in the right hand side, exhibits a markedly different outcome. Prior to the test, this grid displays a strategic distribution of lead mass across its quadrants, as per the present design. After the test, the grid maintains its structural form significantly better than the regular punched grid. The differential mass distribution within the grid wires and frames contributes to enhanced structural rigidity and preferential corrosion, effectively arresting grid growth and extending the service life of the battery. This novel design optimizes current density and corrosion patterns, ensuring that the grid remains functional even under severe testing conditions. Overall, FIG. 3 underscores the technical advancements of the punched grid with distributed mass, demonstrating the punched grid's superior ability to withstand corrosive environments compared to conventional grid designs. The figure highlights the significance of differential mass distribution in enhancing grid durability and performance, offering a promising solution for extending the service life of lead-acid batteries.

The present invention further discloses a method of manufacturing a punched lead grid for a lead-acid battery electrode. This method involves providing a lead strip, reducing the thickness of the lead strip through a rolling process, and then punching the rolled lead strip to form a grid. The grid includes a plurality of grid wires and frame elements arranged to define multiple quadrants. The grid is designed with a differential distribution of lead mass across the quadrants to enhance structural integrity and reduce grid growth.

In one embodiment, the method of manufacturing a punched lead grid for a lead-acid battery electrode begins with casting a lead strip through twin rolls, resulting in an initial thickness between 10 mm and 14 mm. This lead strip is then cold rolled down to a thickness range of 0.7 mm to 1.2 mm using a set of rollers, optimizing the strip for the subsequent punching process. The rolling process can be adjusted to accommodate different lead alloys, such as lead-calcium or lead-antimony, depending on the desired balance between conductivity and durability. The punching process is executed using a progressive punch tool, ensuring precision and consistency in forming the grid wires and frame elements. This tool can be configured to create various grid patterns, such as diamond or square, to suit different battery designs. The differential distribution of lead mass across the quadrants is achieved by varying the width and thickness of the grid wires, tailored to enhance structural integrity and reduce grid growth.

In another embodiment, the method includes an additional step of annealing the punched grid to relieve stresses induced during the punching process, further enhancing the grid's mechanical properties. The method can also be adapted to produce grids with varying numbers of quadrants, allowing for customization based on specific battery performance requirements. Additionally, the grid wires can be coated with a protective layer, such as a thin film of tin, to further improve corrosion resistance and extend the service life of the battery.

The present invention offers several advantages that significantly enhance battery performance which includes the following:
1. Enhanced Structural Integrity: The differential distribution of lead mass across the grid's quadrants imparts significant structural rigidity, reducing the likelihood of grid deformation and ensuring the grid maintains its shape and functionality over time.
2. Reduced Grid Growth: By strategically managing current densities and promoting preferential corrosion in specific quadrants, the invention effectively arrests grid growth, a common issue in lead-acid batteries that can lead to reduced performance and lifespan.
3. Improved Corrosion Resistance: The design optimizes the distribution of current density, which helps manage corrosion patterns and enhances the grid's resistance to degradation, thereby extending the service life of the battery.
4. Optimized Electrical Performance: The arrangement of grid wires, including their angular orientation and discontinuity, contributes to efficient current collection and distribution, improving the overall electrical performance of the battery.
5. Increased Battery Longevity: By addressing common issues such as grid growth and corrosion, the invention enhances the durability and reliability of lead-acid batteries, resulting in longer service life and reduced maintenance needs.
6. Adaptability to Different Applications: The grid design can be tailored to specific battery types and operational conditions, providing flexibility in its application across a wide range of lead-acid battery technologies.
7. Consistent Quality and Performance: The use of a progressive punch tool in the manufacturing process ensures precision and consistency in the formation of grid wires and frame elements, contributing to the high quality and reliability of the final product.
,CLAIMS:
1. A punched lead grid for a lead-acid battery electrode, comprising:
a grid body formed from a rolled lead strip;
a plurality of horizontal and vertical grid wires and frame elements arranged to define multiple quadrants;
wherein each quadrant has a differential distribution of lead mass.

2. The punched lead grid as claimed in claim 1, wherein the first quadrant, positioned nearest to the grid lug, comprises between 32% and 40% by weight of the total lead mass of the grid.

3. The punched lead grid as claimed in claim 1, wherein the second quadrant comprises between 20% and 25% by weight of the total lead mass of the grid.

4. The punched lead grid as claimed in claim 1, wherein the third quadrant, positioned farthest from the grid lug, comprises between 12% and 18% by weight of the total lead mass of the grid.

5. The punched lead grid as claimed in claim 1, wherein the fourth quadrant comprises between 25% and 28% by weight of the total lead mass of the grid.

6. The punched lead grid as claimed in claim 1, wherein the horizontal wires are arranged at a specific angle relative to the vertical wires, contributing to the reduction of grid growth on the width side by optimizing the distribution of mechanical stress and current density.

7. The punched lead grid as claimed in claims 1 to 6, wherein the plurality of grid wires comprises plurality of horizontal and vertical wires.

8. The punched lead grid as claimed in claims1 to 7, wherein the horizontal wires are made discontinuous, touching the side vertical frames.

9. The punched lead grid as claimed in claims 1 to 8, wherein the horizontal wires are alternatively extended to the lug side horizontal frames.

10. The punched lead grid as claimed in claims 1 to 9, wherein the horizontal wires are arranged at an angle ranging from 70-90 degree relative to the vertical wires.

11. The punched lead grid as claimed in claim 1, wherein the differential distribution of lead mass is configured to impart structural rigidity and to establish differential current densities that facilitate preferential corrosion in selected quadrants and thereby arrest grid growth and enhanced service life of the battery.

12. A method of manufacturing a punched lead grid for a lead-acid battery electrode, comprising:
providing a lead strip;
reducing the thickness of the lead strip through a rolling process;
punching the rolled lead strip to form a grid with a plurality of grid wires and frame elements arranged to define multiple quadrants;
configuring the grid with a differential distribution of lead mass across the quadrants to enhance structural integrity and reduce grid growth.

13. The method as claimed in claim 12, wherein the rolling process reduces the thickness of the lead strip to between 0.7 mm and 1.2 mm, optimizing the strip for subsequent punching.

14. The method as claimed in claim 12, wherein the punching process is performed using a progressive punch tool, ensuring precision and consistency in the formation of the grid wires and frame elements.

15. The method as claimed in claim 12, wherein the differential distribution of lead mass is achieved by varying the width and thickness of the grid wires in each quadrant, tailored to enhance structural integrity and reduce grid growth.