Nokia 2160 Owner's Manual page 14

Leaving the battery in hot or cold places, such as in a
closed car in summer or winter conditions, reduces the
capacity and lifetime of the battery. Always try to keep
the battery between 59 F and 77 F (15 C and 25 C). A
phone with a hot or cold battery may temporarily not
work, even if the battery is fully charged. NiMH battery
performance is particularly limited in temperatures
below 14 F (-10 C).
The battery is a sealed unit with no serviceable parts.
Do not attempt to open the case.
Do not dispose of a battery in a fire! Dispose of used
batteries in accordance with local regulations. Recycle!
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