Dry charged negative plates

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... 

SLI batteries are also supplied in a dry charged state and are activated simply by filling with electrolyte. Plates for such batteries have extra additives, such as antioxidants in the negative active mass, and forming is followed by one of a number of controlled drying processes. 

Fig. 4.3. Schematic of dry rod and plate electrostatic precipitator (after Oglesby and Nichols, 1978). The rods have sharp horizontal protrusions (nails) which promote corona formation. Dusty gas flows between the plates and around the rods. A large electrical potential (60 000 V) is applied between the rods and plates. This negatively charges the dust particles - causing them to approach and adhere to the positive collection plates. The dust is gathered by periodically rapping the plates, causing sheets of dust to fall into dust bins below, Fig. 4.4. Table 4.2 gives industrial precipitation data.

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. 

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

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. 

The components of a reserve zinc/silver oxide cell consist of the positive plates, the negative plates, and the separators. The components are assemhled such that each negative plate is protected from direct contact with the adjacent positive plate by a separator. The cell components are assembled and packaged in a container the plates can be prepared in either a dry and charged condition or dry and uncharged condition. 

Tank-formed groups or plates are somewhat unstable (negatives will spontaneously oxidize in air) and therefore are dry charged before use (see Sec. 23.3.11). 

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