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There is some misconception about the
word "memory". Memory is commonly blamed for all
battery failures known to man. Originally, the word memory
was derived from cyclic memory, meaning that a
NiCd battery can remember how much discharge was required
on previous discharges. Improvements in battery technology
have virtually eliminated this phenomenon. Tests performed
at a Black & Decker lab, for example, showed that the
effects of "cyclic memory" were so minute that they
could only be detected with sensitive instruments. After the
same battery was discharged for different lengths of time,
the cyclic memory phenomenon could no longer be detected.
The problem with the modern NiCd battery
is not the cyclic memory but the effects of crystalline
formation. (When memory is mentioned we refer to crystalline
formation.) The active materials of a NiCd battery (nickel
and cadmium) are present in crystalline form. When the memory
phenomenon occurs, these crystals grow, forming spike or tree-like
crystals that cause the NiCd to gradually lose performance.
In advanced stages, these crystals may puncture the separator,
causing high self-discharge or an electrical short.
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