Lead pasted plates

Figure 6. Vacuum mixer for lead paste 1, mixing compartment 2, fast-rotating mixing tools 3, material-deflecting plate 4, discharge opening 5, static, vacuum-sealed enclosure [21J.

The production of tubular positive plates is in principle similar to that of pasted plates. A number of manufacturers use the same gray oxide as the basic filling substance. Sometimes the share or red lead or minium (Pb304) is increased above 25 or even to 100wt.%. The latter is more economic when the manufacturer runs his own minium plant then the expense of the chemical oxidation of lead oxide (PbO) to minium (Pb304) may be compensated by reduced formation cost. Furthermore, curing is not required, because of the high oxidation state, and the battery starts with full capacity when formed. 

The classical scheme for the manufacture of flat pasted plates for automotive, traction and stationary lead-acid batteries is shown in Fig. 3.1. There is no difference between the technology of plate manufacture for conventional (flooded) and valve-regulated (VRLA) lead acid batteries. The two versions do differ, however, in the method of separation of the plates, the quantity and type (hquid or gel) of electrolyte, and in the design of the battery itself. 

Positive and negative active-mass formation. The cured pastes of both positive and negative plates comprise identical mixtures of bivalent lead compounds (3BS, 4BS, PbO), which cannot create electromotive forces when the pasted plates are assembled into cells. The purpose of the formation step is to convert the cured pastes into electrochemically active porous materials — Pb02 in the positive plates and Pb in the negative plates — which are connected mechanically and electrically to the grids. The process of formation can be conducted via two basic schemes, as shown in Fig. 3.1. 

SLI plates were kept in contact with air for different periods of time. The obtained kinetic curves of oxidation of the plates by the air are presented in Fig. 13.6. After reaching a definite critical temperature and moisture content, a vigorous oxidation or burning of the plates commences. This phenomenon is quite similar to the processes observed during curing of the pasted plates. At the end of this period of rapid oxidation, the active mass contains 50—60% sponge lead and up to 40—50% lead oxide and lead sulfate. This composition of the negative active mass yields only a very low capacity, and often none at all. 

Tubular positive plates are sometimes used in batteries for deep-discharge applications to reduce shedding of electro-active materials from the plate during cycling. The positive electrode has intercoimected porous tubes that are filled with positive lead paste. Lead rods in the centers of tubes are connected in parallel by a conductive lead bar at the top, and the bar is connected to the positive terminal. 

Table 2.5 Lead-acid traction batteries, monobloc battery with pasted plates (DIN 43594).

Pure lead is generally too soft to be used as a grid material. Exceptions that use pure lead plates are some special, very thick plate Plants or pasted-plate batteries, some small spiral wound batteries, some valve regulated cells and batteries (see Fig. 23.12c) and a cylindrical cell. The latter were developed by Bell Laboratories (now part of Lucent Technologies) (see Fig. 23.36). "... 

FIGURE 23.24 Flat-pasted-plate lead-acid traction battery. (Courtesy of C D Technologies.)... 

FIGURE 23.40 Performance curves of lead-acid stationary batteries at 25°C (S-shaped curves, based on positive-plate performance), (a) Antimony flat-pasted plate, 125 Ah at 8-h rate 290-mm height, 239-mm width, 8.6-mm thickness. Courtesy of Enersys, Inc.)... 

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