Nokia 2135 User Manual page 48

If a battery is being used for the first time or if the battery has
not been used for a prolonged period, it may be necessary
to connect the charger, then disconnect and reconnect it
to begin charging the battery. If the battery is completely
discharged, it may take several minutes before the charging
indicator appears on the display or before any calls can
be made.
Always switch the device off and disconnect the charger
before removing the battery.
Unplug the charger from the electrical plug and the device
when not in use. Do not leave a fully charged battery
connected to a charger, since overcharging may shorten
its lifetime. If left unused, a fully charged battery will lose
its charge over time.
Use the battery only for its intended purpose. Never use
any charger or battery that is damaged.
Always try to keep the battery between 59°F and 77°F
(15°C and 25°C). Extreme temperatures reduce the capacity
and lifetime of the battery. A device with a hot or cold battery
may not work temporarily. Battery performance is particularly
limited in temperatures well below freezing.
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