Page 406 - Battery Reference Book

Carbon-zinc primary batteries 36/3
These batteries retain the great majority of the primary size) types on a 10 R 2Wday discharge; the advantage
battery market for portable-in-use applications. They of using the high-power type is obvious. For low-rate
are widely available in a variety of equivalent cylin- discharges, the additional cost of the HP version is not
drical sizes. warranted; Figure 36.3 compares the same cells on the
The earlier carbon-zinc system has the property 300 C2 2 Wday discharge.
of ‘recovering’ during rest periods in the discharge Transistor applications require multiples of the unit
regimen. This property and the low cost resulting cell voltage; the layer stack (‘power pack’) format
from high-volme automated manufacture make the provides a convenient battery in a smaller volume
earlier carbon-zinc systems ideal for the intermit- than the equivalent combination of round cells. Only
tent usage pattern found in most consumer appli- one unit needs to be replaced, and connection is
ances. Figure 36.1 shows the effect of increased cnr- by simple non-reversible press studs ensuring correct
rent drain on service life of the SP2 (R20 size) bat- polarity. Selection of the most economical layer stack
tery. The dischzge period is 5 Wday to an end-voltage battery should be made in conjunction with the battery
of 0.9 V. manufacturer. Specification of a battery which is too
For higher current drains, for example in motorized small for the current drain can lead to unnecessarily
equipment, a hngh-power (HP) battery should be used. frequent battery replacement. Figure 36.4 shows the
HP batteries contain electrolyte or chemically prepared comparative service lives of two 9 V power packs, PP9
manganese dioxides, which have enhanced discharge
properties. Figure 36.2 compares SP11 and HPll (R14
1.6
loo 90 t - 1.5

1.4
-
> 1.3

20 Percentage of service life
10 Figure 36.3 Low discharge effect. SP11 and HP11 (R14) aikaline
0 20 40 60 80 100 manganese batteries: effect of using a high-power battery (HPII)
Percentage of service life on service life at high current drain (300 S2, 2 h/day discharge)
Figure36.1 Effect of increased current drain on service life of
SP2 (R20) Leclanche cells

0 20 40 60 80 100
Percentage of service life
Percentage of service life
Figure36.2 Heavy duty effect. SP11 and HPll (R14) alkaline
manganese battenes. beneficial effect of using a high-power Figure 36.4 Size effect of Lecianch6 batteries: comparative
battery (HP11) or service life at high current drain (loa, 2 h/day service lives of two 9V power packs, PP9 and PP6, on a 450 Q,
discharge) 4 hlday discharge