ABSTRACT

The as-cast grain structures, such as those produced by the Multialloy strip caster, exhibit (I) higher resistance to recrystallization caused by elevated temperatures and (2) higher creep resistance [318,322]. Continuous processes are inherently lower in production cost than the conventional book-mold or gravity-cast technologies. The lighter weight of the strip cast and rotary expanded grids allows one to pack more grid plates/battery. To maximize cold crank performance, the rotary expanded grid is designed to have a low-electrical-resistance design. Small diamonds minimize the effect of the less conductive paste. In addition, differential width diamond wires assist cold crank performance by increasing conductive capacity in the higher-current-density areas of the grid. Typically, the width decreases from 1.8 mm at the top of the grid, to l.l mm in the middle, to 0.9 mm at the bottom (Figure 23) [312]. The small diamond grid assists paste retention by simply increasing the grid wire-paste interface. Paste retention is further assisted by an irregular, nonftat-surface helical twist in the rotary expanded grid. Higher paste retention improves battery life. The negative grid is not as sensitive to design as the positive, although this grid has also seen a

Figure 23 Differential width diamond-grid-wire structure [318]. (Courtesy of Cominco, Missisauga, ON, Canada.)