Page 205 - Lindens Handbook of Batteries

AN INTRODUCTION TO PRIMARY BATTERIES 8.17

1500

1100
Zn/Air

Li/SOCl 2
800 (spiral-wound)
Energy density, Wh/L 600 Li/MnO 2

2
Li/SO
2
400 Zn/Ag O
Zn/alk/MnO 2
Zn/HgO
200 Mg/MnO 2
Zn-carbon

–40 –20 0 20 40 60
Temperature, °C
FIGURE 8.9 Volumetric energy density of primary battery systems.

8.3.7 Shelf Life of Primary Batteries
The shelf-life characteristics of the major primary battery systems are plotted in Fig. 8.10 and show
the rate of loss (in terms of percentage capacity loss per year) from 20 to 70°C. The relationship is
approximately linear when log capacity loss is plotted against log 1/T (temperature, °Kelvin). The
data assume that the rate of capacity loss remains constant throughout the storage period, which is
not necessarily the case with most battery systems. For example, as shown in Chap. 14 for several
lithium batteries, the rate of loss tapers off as the storage period is extended. The data are also a
generalization of the capability of each battery system under manufacturer-rated conditions because
of the many variations in battery design and formulation. The discharge conditions and size also
have an influence on charge retention. The capacity loss is usually highest under the more stringent
discharge conditions.
The ability to store batteries improves as the storage temperature is lowered. Cold storage of bat-
teries is used to extend their shelf life. Moderately cold temperature, such as 0°C, was usually used
as freezing could be harmful for some battery systems or designs. As the shelf life of most batteries
has been improved, manufacturers are no longer recommending cold storage but suggest room tem-
perature storage is adequate provided that excursions to high temperature are avoided.

8.3.8 Cost

Consumer Reports conducts tests on different types of commercial primary and secondary batteries
for applications such as digital cameras. The results are compared on a basis of the cost effectiveness
of a particular type in the given application. The most recent study for digital camera is given in the
Dec. 2009 issue, but results are updated regularly. See also Chap. 32.