Zinc-carbon batteries discharging

FIGURE 8.12 General purpose D-size zinc-carbon battery discharged through 3.9 ohm at 20 C, under various discharge conditions. 

FIGURE 8.15 Zinc-carbon batteries, discharged under simulated cassette application (10 ohm intermittent load) at 20°C. 

FIGURE 8.29 Service hours for general-purpose zinc-carbon battery, discharged 2 h/day to 0.9 V at 20°C. 

FIGURE 3.15 Discharge characteristics of a 9-volt battery subjected to a 100 ms pulse (smoke detector pulse tests) (a) zinc-carbon battery (b) and (c) zinc/alkaline/ manganese dioxide battery. 

Industrial Heavy Duty. Application Intermittent medium- to heavy-rate discharges, low to moderate cost. The industrial heavy-duty zinc-carbon battery generally has been converted to the zinc chloride system. However, some types continue to include ammonium chloride and zinc chloride (ZnCl2) as the electrolyte and synthetic electrolytic or chemical manganese dioxide (HMD or CMD) alone or in combination with natural ore as the cathode. Its separator may be of starch paste but it is typically a paste-coated paper liner type. This grade is suitable for heavy intermittent service, industrial applications, or medium-rate continuous discharge. 

FIGURE 8.8 Typical discharge curve of a Leclanche zinc-carbon battery. 

Performance of zinc-carbon batteries varies depending upon the type of discharge. The performance of Leclanche batteries is significantly better when used under intermittent compared to continuous discharge conditions, because (1) a chemical recuperation reaction replaces a small portion of active ingredients during the rest periods and (2) transport phenomena redistribute reaction products. ... 

FIGURE 8.11 Battery performance (capacity to 0.9 V) as a function of discharge, load and duty schedule for a general purpose D-size zinc-carbon battery at 20°C. From Eveready Battery Energy Data.)... 

FIGURE 8.14 Zinc-carbon batteries, continuous discharge through 150 ohm at 20°C. 

FIGURE 8.25 Comparison of general-puipose D-size zinc-carbon batteries of five different manufacturers, discharged on the ANSI LIF test through 2.2 ohm load at 20 U. 

Zinc-carbon batteries perform better on intermittent drains than continuous drains, largely because of their ability to dissipate the effects of polarization. Factors that affect polarization are identified earlier in this section. Resting between discharges allows the zinc surface to depolarize. One such effect is the dissipation of concentration polarization at the anode surface. This effect is more pronounced as heavier drains and longer duty schedules are... 

The internal resistance of zinc-carbon batteries increases with the depth of discharge. Some applications use this feature to estabUsh low battery alarms to predict near end of battery life situations (such as in the smoke detector). Fig. 8.27 shows the relative battery internal resistance versus depth of discharge of a 9-V Leclanch6 battery. 

Zinc-carbon batteries are made in a number of different sizes with different formulations to meet a variety of applications. The single-cell and multicell batteries are classified by electrochemical system, either Leclanche or zinc chloride, and by grade general purpose, heavy duty, extra heavy duty, photoflash, and so on. These grades are assigned accortUng to their output performance under specific discharge conditions. 

Figure 38.17 is a side view of a flat-pack cell. Figure 38.18 compares the performance of a 6-V four-cell hybrid lantern battery with similar alkaline and zinc-carbon batteries at an intermittent low-rate discharge. The specific energy of this battery is about 350 Wh/kg. Single and multicell batteries are available in capacities of 40 to 4800 Ah. 

Depending on the composition of the active materials and on the manganese dioxide type employed, the OCV of freshly manufactured zinc-carbon cells with salt electrolyte varies between 1.55 and 1.85 V. It decreases during discharge and formation of the variable-composition mass. Upon prolonged storage of undischarged batteries, their OCV also decreases. 

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