Direct cast lead alloy strip for expanded metal battery plate grids

Abstract

A method of making a lead alloy grid for use in a plate for a lead acid battery that enables thin battery plates with a high surface area. The method of the present invention includes forming the lead alloy, such as by direct casting, to a very small thickness, then work hardening the cast strip to create a grid by forming indentations and protrusions in the thinly cast alloy strip, which in addition to strengthening the strip, provides a desirable surface topography for paste adhesion and interface characteristics. The work hardening, for example embossing, may further include splitting the strip at a high point of the protrusions and indentations to create perforated protrusions and indentations. The grid may then be used to make a plate by pasting an active mass onto the grid, steaming the pasted grid, and curing the pasted grid to provide a plate having a thickness of about 0.05 inch or less. There is further provided a lead alloy grid for use in a plate of a lead acid battery, the grid comprising a cast lead-tin-calcium alloy having spaced protrusions and indentations on each opposing surface of the grid. The protrusions and indentations may further include a perforation. The grid has a higher surface area than punched or expanded grids, thereby providing a lower resistance and better adherence at the paste/grid interface.

1 . A method of making a lead alloy grid for use in a plate of a lead acid battery, comprising the steps of: 
 forming a strip of a lead-tin-calcium alloy; and    forming a plurality of indentations in a surface of the strip.    
     
     
         2 . The method of  claim 1  wherein the alloy is Pb-1.5Sn-0.08Ca.  
     
     
         3 . The method of  claim 1  wherein forming the strip includes direct casting the alloy.  
     
     
         4 . The method of  claim 3  wherein the alloy is direct cast to a thickness in the range of about 0.005-0.015 inch.  
     
     
         5 . (Cancelled).  
     
     
         6 . The method of  claim 1  further comprising forming perforations within the indentations.  
     
     
         7 . The method of  claim 1  wherein the plurality of indentations are formed in each of the opposing surfaces of the strip.  
     
     
         8 . The method of  claim 1  further comprising, prior to forming the indentations, rolling the strip to reduce its thickness.  
     
     
         9 . The method of  claim 8  wherein the rolling reduces the strip to a thickness in the range of about 0.005-0.015 inch.  
     
     
         10 . The method of  claim 1  wherein forming the indentations includes embossing the surface to form pyramid-shaped indentations each having a central indented area surrounded by four angled surfaces.  
     
     
         11 . The method of  claim 10  wherein the embossing further includes splitting the strip in the central indented areas to form perforated indentations.  
     
     
         12 . The method of  claim 1  wherein the work hardening includes embossing the surface to form diamond-shaped indentations each having a central indented point surrounded by four angled surfaces.  
     
     
         13 . The method of  claim 12  wherein the embossing further includes splitting the strip at the central indented points to form perforated indentations.  
     
     
         14 . The method of  claim 1  wherein work hardening includes embossing the surface to form hemispherical-shaped indentations.  
     
     
         15 . The method of  claim 1  wherein work hardening includes knurling the surface.  
     
     
         16 . A method of making a plate for a lead acid battery comprising the steps of applying an active mass paste to a lead alloy grid formed by the method of  claim 1  to form a pasted grid, then steaming the pasted grid, and curing the pasted grid.  
     
     
         17 . A method of making a plate for a lead acid battery comprising the steps of applying an active mass paste to a lead alloy grid formed by the method of  claim 4  to form a pasted grid, then steaming the pasted grid, and curing the pasted grid, wherein the cured pasted grid has a thickness of about 0.05 inch or less.  
     
     
         18 - 27 . (Cancelled).  
     
     
         28 . A lead alloy grid for use in a plate of a lead acid battery, the grid comprising a cast lead-tin-calcium alloy having on each of opposing surfaces a pattern of spaced protrusions and indentations.  
     
     
         29 . (Cancelled).  
     
     
         30 . The grid of  claim 28  wherein the protrusions and indentations are evenly spaced apart at a distance of about 0.01-0.03 inch.  
     
     
         31 . The grid of  claim 28  wherein the alloy is Pb-1.5Sn-0.08Ca.  
     
     
         32 . The grid of  claim 28  further including a perforation at a high point of each of the protrusions and indentations.  
     
     
         33 . The grid of  claim 28  wherein the protrusions and indentations are pyramid-shaped, each having a central area surrounded by four angled surfaces.  
     
     
         34 . The grid of  claim 33  further including a perforation in each central area.  
     
     
         35 . The grid of  claim 28  wherein the protrusions and indentations are diamond-shaped, each having a central point surrounded by four angled surfaces.  
     
     
         36 . The grid of  claim 35  further including a perforation at each central point.  
     
     
         37 . The grid of  claim 28  wherein the protrusions and indentations are hemispherical-shaped.  
     
     
         38 . A plate for a lead acid battery comprising a cured active mass on the lead alloy grid of  claim 28 , wherein the plate has a thickness of about 0.05 inch or less.  
     
     
         39 . (Cancelled).