Page 413 - Lindens Handbook of Batteries

14.78 PriMAry BATTerieS

activates, its resistance increases sharply, with a corresponding reduction in the flow of current and,
consequently, internal heat generation. When the battery (and the PTC) cools, the PTC resistance
drops, allowing the battery to discharge again. The PTC will continue to operate in this manner for
many cycles if an abusive condition continues or recurs. The PTC will not “reset” indefinitely, but
when it ceases to do so, it will be in the high-resistance condition. The characteristics of PTCs (or
any other current-limiting devices in the battery) may place some limitations on performance. These
are discussed in more detail in Sec. 14.10.3.

14.10.3 Performance

Voltage. The nominal voltage of the Li/FeS system is given as 1.5 V and the open-circuit voltage
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of undischarged cells is approximately 1.78 V. The voltage on load drops within milliseconds, as
shown in Fig. 14.77.

FIGURE 14.77 On-load voltage of Li/FeS AA-size cells. (Courtesy of Energizer Battery Co., Inc.)
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Discharge. Li/FeS batteries typically have a higher operating voltage and a flatter discharge pro-
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file than aqueous zinc/alkaline manganese dioxide 1.5 V batteries. This is illustrated in Fig. 14.78
which compares the performance of these two battery systems at relatively light and heavy constant-
current discharge rates. These characteristics of the Li/FeS battery result in higher energy and power
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output, especially on heavier drains where the operating voltage differences are greatest.
Performance characteristics of AA Li/FeS batteries under constant-current and constant-power
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discharge modes are Figs. 14.79 and 14.80. The improvement to performance with time on an ANSi
digital still camera (DSC) test is shown in Fig. 14.81.
Operating Temperature. Li/FeS batteries are also suitable for use over a broad temperature range,
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generally -40 to 60°C. Service life is improved at elevated temperatures. in some applications there
may be further limits on the maximum discharge temperature due to current limiting, which are part