Battery grids negative

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. 

The major components in a lead-acid battery include a positive grid, negative grid, positive active material, negative active material, electrolyte, top lead, separator, and plastic container. The weight distributions of conunon SLI batteries and traction batteries are shown in Figure 1.18. 

The positive plates are siatered silver on a silver grid and the negative plates are fabricated from a mixture of cadmium oxide powder, silver powder, and a binder pressed onto a silver grid. The main separator is four or five layers of cellophane with one or two layers of woven nylon on the positive plate. The electrolyte is aqeous KOH, 50 wt %. In the aerospace appHcations, the plastic cases were encapsulated in epoxy resins. Most usehil cell sizes have ranged from 3 to 15 A-h, but small (0.1 A-h) and large (300 A-h) sizes have been evaluated. Energy densities of sealed batteries are 26-31 W-h/kg. 

Most grids are cast or mechanically expanded from cast or wrought strip. Historically, negative and positive grids have been the same however, with the advent of specialized batteries and extreme performance demands, this is less likely. However if these plates are different, it is generally in configuration, alloy, and/or thickness. 

The network of lead wires must provide optimum mechanical support to the pellets of active material that fill the void space. Sufficient conductivity has also to be provided by the grid. Grids for positive and negative electrodes are usually similar. In batteries designed for extended service life, the positive grid is made heavier to provide a corrosion reserve. For very thin electrodes, a lead foil is used as the substrate and current conductor. 

Fig. 5.13 Motive power lead-acid cell with tubular positive plates in which the active material is contained in pre-formed terylene tubes, and negative pasted grid plates surrounded by microporous polyvinyl chloride separator envelopes. The case and lid are formed of heat-sealed polypropylene. (By courtesy of Chloride Industrial Batteries.)...

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