Positive plate capacity

The data in Fig. 2.34 suggest that H2SO4 is absorbed in the gel zones of Pb02 particles and alters the ratio gel/crystal zones, which will affect the capacity of the plates. It can be expected that the positive plate capacity will depend on the concentration of the H2SO4 electrolyte, especially at high concentration levels. 

Traction or motive power batteries are made in many different sizes, limited only by the battery compartment size and the required electrical service. The basic rating unit is the positive-plate capacity, given in amp-hours at the 5- or 6-h rate. The 2-V cell in the traction batteries is grouped with 2 to 16 positive plates, or 5 to 33 positive and negative plates. Traction batteries are often assembled to have battery voltage in... 

Traction or motive-power batteries are made in many different sizes, limited only by the battery compartment size and the required electrical service. The basic rating unit is the positive-plate capacity, given in Ampere-hours at the 5- or 6-h rate. Table 23.14a lists the typical U.S. traction plate sizes using flat-pasted plates between 5 and 33 plates are used to assemble traction cells, as also shown in the table. Ratings of the cell are the product of the capacity of a single positive plate multiplied by the number of positive plates. The cells, in turn, are assembled in a variety of battery layouts, with typical voltage in 6-V increments (e.g., 6, 12, 18 to 96 V) resulting in almost 1000 battery sizes. Popular traction battery sizes are the 6-cell, 11-plates-per-cell, 75-Ah positive-plate (375-Ah cell) and the 6-cell, 13 plates-per-cell, 85-Ah positive-plate (510-Ah cell) batteries. Table 23.146 presents similar information on the tubular positive-plate batteries. 

Positive-plate capacity, Ah at 6-h rate Plate dimensions, mm Cell size, t (positive plates per cell)... 

Some manufacturers add a small (10—20% of the positive loading) amount of cadmium to positive plates as an antipolar mass to prevent some of the problems of reversal in sealed cells. This practice may, however, create as many problems as it solves in that positive capacity is reduced proportionally to the quantity of antipolar mass added. 

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 dipole moment of a molecule can be obtained from a measurement of the variation with temperature of the dielectric constant of a pure liquid or gaseous substance. In an electric field, as between the electrostatically charged plates of a capacitor, polar molecules tend to orient themselves, each one pointing its positive end toward the negative plate and its negative end toward the positive plate. This orientation of the molecules partially neutralizes the applied field and thus increases the capacity of the capacitor, an effect described by saying that the substance has a dielectric constant greater than unity (80 for liquid water at 20°C). The dipole moments of some simple molecules can also be determined very accurately by microwave spectroscopy. 

Pocket plate design is not suitable for the positive electrode because of the infiltration of soluble zincate and the consequent decrease in positive electrode capacity. Porous matrix positives do not suffer so badly from... 

It is seen that the major effect on peak shape is the "detector cell capacity V column plate capacity" ratio, (CJ. When the capacity of the detector cell is less than the plate capacity of the column, (C <1), the negative part of the signal dominates, and when the detector cell capacity exceeds the column plate capacity, (C >1), the positive part of the signal dominates. For this reason when (C >1), the integral curve rises to a maximum but does not return to the baseline. Conversely, when (C <1), the integral curve first rises and then falls below the baseline and does not return. 

Pb02. -Pb02 ratio and its effect on capacity of positive plates... 

Fig. 3.19. Capacity of positive plates at second charge-discharge cycle as a function of acid-to-oxide ratio in paste [34].

Fig. 3.33. (a), (b) Phase composition of pastes prepared with different amounts of acid at 30 and 80°C (c), (d) Changes in C20 capacity of 12-V/42-Ah automotive batteries with positive plates produced from 3BS, 4BS, and IBS pastes (depending on acid strength and preparation temperature) on cycling at 50% DoD. The battery capacity is limited by the positive plates [34]. 

In positive-plate manufacture, 3BS and 4BS phases are never used alone. They are always in combination with PbO, which improves the connection between the basic lead sulfate crystals and hence facilitates the formation of a mechanically strong porous mass or skeleton. The ratio between the basic lead sulfates and the PbO in the pastes exerts an influence on the initial capacity and the cycle-life performance of the battery, namely the higher the PbO content in the paste, the lower is the initial capacity of the positive plates (Fig. 3.33). 

It has been established that on cycling of tubular positive plates with die-cut strap grids (SGTP) or of positive plates with expanded grids with flat ribs, a rapid capacity loss is observed (the PCL-1 effect, see Section 2.3, Chapter 2 and Chapter 9) [54]. The reason for this capacity loss is the formation of groups of PbS04 crystals in the layer of the PAM that contacts the current-collector (Fig. 3.39). These PbS04... 

Fig. 3.4L Capacity curves for strap grid tubular positive plates (SGTP) (a) cast strap grids with smooth surface (b) die-cut strap grids with smooth surface (PCL-1 effect) (c) die-cut strap grids with rough surface obtained after reverse-current treatment prior to formation proper [54].

Fig. 3.60. Positive-plate potential during constant-current formation and initial capacity of four different types of cured pastes [5]. The former data show the decline in potential after the maximum value.

---