Lead acid battery grids

Automobile battery grids employ about 1—3 wt % antimony—lead alloys. Hybrid batteries use low (1.6—2.5 wt %) alloys for the positive grids and nonantimony alloys for the negative grids to give reduced or no water loss. The posts and straps of virtually all lead—acid batteries are made of alloys containing about 3 wt % antimony. 

Lead alloys containing 0.09—0.15 wt % calcium and 0.015—0.03 wt % aluminum are used for the negative battery grids of virtually all lead—acid batteries in the United States and are also used in Japan, Canada, and Europe. If the molten alloy is held at too low a temperature, the aluminum precipitates from solution, rises to the surface of the molten alloy as finely divided aluminum particles, and enters the dross layer atop the melt. 

Silver reduces the oxygen evolution potential at the anode, which reduces the rate of corrosion and decreases lead contamination of the cathode. Lead—antimony—silver alloy anodes are used for the production of thin copper foil for use in electronics. Lead—silver (2 wt %), lead—silver (1 wt %)—tin (1 wt %), and lead—antimony (6 wt %)—silver (1—2 wt %) alloys ate used as anodes in cathodic protection of steel pipes and stmctures in fresh, brackish, or seawater. The lead dioxide layer is not only conductive, but also resists decomposition in chloride environments. Silver-free alloys rapidly become passivated and scale badly in seawater. Silver is also added to the positive grids of lead—acid batteries in small amounts (0.005—0.05 wt %) to reduce the rate of corrosion. 

The excellent corrosion-resistant lead dioxide, Pb02, film formed on anodes and lead—acid battery positive grids in sulfuric acid has enabled lead insoluble anodes and lead—acid batteries to maintain the dominant positions in their respective fields. 

Selenium acts as a grain refiner in lead antimony alloys (114,115). The addition of 0.02% Se to a 2.5% antimonial lead alloy yields a sound casting having a fine-grain stmcture. Battery grids produced from this alloy permit the manufacture of low maintenance and maintenance-free lead—acid batteries with an insignificant loss of electrolyte and good performance stability. 

Trace quantities of arsenic are added to lead-antimony grid alloys used ia lead—acid batteries (18) (see Batteries, lead acid). The addition of arsenic permits the use of a lower antimony content, thus minimising the self-discharging characteristics of the batteries that result from higher antimony concentrations. No significant loss ia hardness and casting characteristics of the grid alloy is observed (19,20). 

Barium improves the performance of lead ahoy grids of acid batteries (see Batteries) (34). In the form of thin films, barium has been found to be a good high temperature lubricant on the rotors of anodes operating at 3500 rpm ia vacuum x-ray tubes (35). 

Fig. 5. Lead—Acid battery grid design variations showing A lugs, B feet, C frames, and D current carrying wire for (a) rectilinear design, (b) corner lug radial, (c) center lug radial, (d) corner lug expanded metal, and (e) plastic/lead composite.

The conductivity of the grid plays a substantial role in a battery s abiUty to meet high current demands. The importance of grid conductivity for lead—acid batteries has been discussed (1,69). Composition and configuration are important design factors impacting grid conductivity. 

The proper selection of the lead alloy depends on the intended use and the economics of the lead—acid battery appHcation. The metallurgical and electrochemical aspects of the lead are discussed in the Hterature in a comprehensive manner (81,85—87) as are trends of lead alloy use for manufacture of battery grids (88). 

The tubular positive plate uses rigid, porous fiber glass tubes covered with a perforated plastic foil as the active material retainer (Fig. 2). Dry lead oxide, PbO, and red lead, Pb O, are typically shaken into the tubes which are threaded over the grid spines. The open end is then sealed by a polyethylene bar. Patents describe a procedure for making a type of tube for the tubular positive plate (90) and a method for filling tubular plates of lead—acid batteries (91). Tubular positive plates are pickled by soaking in a sulfate solution and are then cured. Some proceed directiy to formation and do not requite the curing procedure. 

R. T. Johnson and. R. Pierson, "The Impact of Grid Composition on the Performance Attributes of Lead—Acid Batteries," iu L. J. Pearce, ed.. Power Sources 11, International Power Sources Symposium Committee, 1987. 

Unlike the automobile-type battery that is quite portable, the stationaiy lead-acid batteries that provide uninterruptible power to hospitals and other important facilities are not. Some may weigh over several tons because of the much heavier grid structure and other features to extend life expectancy and improve deep discharge capabilities. 

The plate support in lead-acid batteries is usually called the "grid". In most batteries the grid has to provide both mechanical support for the active material and electronic conductivity for the collected current. 

Figure 5. Grid of a lead-acid battery with thicker walls and a rectangular mesh. One corner and cross-sections in vertical and horizontal directions (from 1151).

Since grid material is converted into lead dioxide, a slight increase in the actual capacity is often observed with lead-acid batteries. The reduced cross-section in Fig. 9 does not affect the performance of batteries that are used for discharge durations in the order of one hour or more. Attention must, however, be paid to batteries that are loaded with high currents, because the conductivity of the grid gains importance with increased current flow. 

Let us note finally, that tellurium has been considered as an appropriate component for the lead grid alloy in lead-acid batteries, as improving its durability, mechanical strength, and anti-corrosive ability. In investigating Pb-Te binary alloys with different contents of Te (0.01-1.0 wt%) in sulfuric acid solution it was shown recently [104] that the introduction of Te can inhibit the growth of Pb02 and increase corrosion resistance of the positive grid alloy of a lead-acid battery. By the... 

As the name suggests, the materials used in a lead-acid battery include lead and an acid. Figure 11.19 shows that the electrodes in each cell are constructed using lead grids. One electrode consists of powdered lead packed into one grid. The other electrode consists of powdered lead(IV) oxide packed into the other grid. The electrolyte solution is fairly concentrated sulfuric acid, at about 4.5 mol/L. 

The most important use of barium is as a scavenger in electronic tubes. The metal, often in powder form or as an alloy with aluminum, is employed to remove the last traces of gases from vacuum and television picture tubes. Alloys of barium have numerous applications. It is incorporated to lead alloy grids of acid batteries for better performance and added to molten steel and metals in deoxidizing alloys to lower the oxygen content. Thin films of barium are used as lubricant suitable at high temperatures on the rotors of anodes in vacuum X-ray tubes and on alloys used for spark plugs. A few radioactive isotopes of this element find applications in nuclear reactions and spectrometry. 

Studies on lead electrodeposition on conducting solid substrates are related mainly to electrocatalysis, searching for alternative collectors/grids for lead-acid batteries, as well as for removing Pb(II) ions from aqueous solutions and stripping for analytical purposes. 

The lead/acid battery used in conventional gasoline-fueled automobiles consists of six 2.05 V cells connected in series (for a 12 V electrical system). The current collectors are lead grids filled, when in the charged condition, with powdered lead (anode) and a lead/lead(IV) oxide mixture (cathode), and the electrolyte is aqueous sulfuric acid. During discharge, the following reactions occur ... 

Fig. 5.4 Typical lead-acid battery grid this acts as a framework to hold the active material in place...

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