Plate drying negative

The drying of negative plates is not possible without precautions, because of the tendency to spontaneous oxidation. This oxidation reaction is much ac-celerated by water, and the active material of a moist negative electrode is spon-taneously converted into lead oxide when exposed to air. When, on the other hand, the charged plate is dry, a thin layer of oxide covers the surface of the active material, and prevents... 

Another study [40] examined the effect of adding lOg of natural graphite with a grain size of 520 pm to positive plates in 4.5-Ah VRLA cells. The active material was prepared by mixing 2kg of leady oxide and 0.8 g of polyester fibre with 150 ml of water and then 271ml of 1.200 rel. dens, sulfuric acid. The pastes were applied to lead-caldum tin grids, cured at 80°C for 72 h, and dried in air. The test cells, composed of one positive and two negative plates, were formed and then floated at a... 

Clearly, this is unacceptable. This is what must be dealt with, however, in properly charging VRLA products. If this thermodynamic fact is not addressed, VRLA products will fail prematurely, not due to dry-out or grid corrosion, but due to insufficient recharge of the negative plate. 

Battery assembly. Dried plates are stacked in active blocks, so that positive and negative plates alternate with separators in between. Plates of like polarity are interconnected into semi-blocks by welding together through the plate lugs. The active blocks are then introduced into battery containers, the cells are connected and the batteries are covered with lids and tested for air-tightness. The vents are closed to eliminate access of air from the surroundings, and the batteries are packed and ready for delivery. 

Methods for Drying Negative Plates After Formation... 

The washed negative plates are loaded in a pressure ehamber equipped with heaters. The latter cause the temperature of the plates to rise above the boiling point of water. The pressure chamber is equipped with a condenser unit where the water vapours are liquefied and drained out. When the pressure chamber is loaded with plates, a vacuum pump is turned on and, after a definite vacuum level is reached, the heaters are turned on, too. The plates are dried for quite a long time (20—24 h) and when no more water condense forms, heating is stopped and the coohng system is turned on. When the temperature in the chamber reaches room temperature, the vacuum pump is stopped. This method is efficient, but too slow and expensive. 

Processes That Occur in the Negative Plates Between the Technological Procedures of Plate Formation and Drying... 

An example of inhibitor treatment of negative plates to prevent oxidation of the sponge lead in the active mass after formation is as follows the washed plates are immersed in a 10—12 wt% solution of boric acid with addition of 1.0—1.5 wt% salicylic acid. The plates are left in this solution for about an hour and are then dried in a drying oven at a temperature of about 130 °C. 

Discharge transients for negative plates of dry-charged batteries after 2 years of storage discharge... 

The active material is produced by dissolutimi of pure iron in sulfuric acid. The FeS04 is recrystallized, dried, and roasted at high temperature to produce Fc203. The materials are washed free of the sulfate, dried, and partiaUy reduced in H2 to produce a mixture of Fe304 and iron. The resulting mixture is blended with small amounts of FeS, sulfur, and HgO for use in negative plate assembly. 

The nickel-iron battery cell fabrication process is essentially unchanged in over 50 years. Special attention must be paid to use high purity materials and particle size characteristics of the active materials. The iron negative active material is made from pure iron that is dissolved in sulfuric acid. The resulting Fe(S04>2 is recrystallized and dried. This is washed free of sulfuric acid and roasted at 915°C to form a mixture of FeaOs and Fe metal and is, then, blended with small amotmts of FeS, sulfur, and HgO for use in the negative plate assembly. 

PbO and Pb), water, sulphuric acid and organic expander and other constituents dependent upon whether the paste is used for positive or negative plates [1]. The plates are then dried, welded together and placed within a case. The battery is shipped in this dry form and is only subsequently filled with sulphuric acid and charged. 

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