Page 289 - Lindens Handbook of Batteries

MERCURIC OXIDE BATTERIES 12.9

1.6

1.4

Voltage, V 1.2

1.0
15 Ω 25 Ω 42 Ω 62.5 Ω 125 Ω
0.8
0.6
20 40 60 80 100
Hours of service
FIGURE 12.8 Discharge curves, zinc/mercuric oxide battery, 1000 mAh size, 20°C.

The capacity or service of the zinc/mercuric oxide battery is about the same on either continuous or
intermittent discharge regimes over the recommended current drain range, irrespective of the duty cycle.
Under overload conditions, however, a considerable shift in available capacity can be realized by
the use of “rest” periods, which may increase service life considerably.
Problems are not encountered at low rates of discharge with batteries designed for the purpose
unless a high-current-drain pulse is superimposed on a continuous low-drain base current; special
designs are necessary to cope with this situation.

12.5.3 Effect of Temperature
The zinc/mercuric oxide battery is best suited for use at normal and elevated temperatures from 15 to
45°C. Discharging batteries at temperatures up to 70°C is also possible if the discharge period is
relatively short. The zinc/mercuric oxide battery generally does not perform well at low tempera-
tures. Below 0°C, discharge efficiency is poor unless the current drain is low. Figure 12.9 shows the
effect of temperature on the performance of two types of zinc/mercuric oxide batteries at nominal
discharge drains.
The wound-anode or “dispersed”-powder anode structures are better suited to high rates and low
temperatures than the pressed-powder anode.

100
90
80
Percent capacity 60 Wound- Water freezes Room temperature
70
anode
50
structures
40
30
20 Pressed powder
10 structures
0
–20 0 20 40 60 80°C
FIGURE 12.9 Effect of temperature on performance of zinc/mercuric oxide batteries.