Zte R621 User Manual page 12

Battery Use
 Do not short-circuit the battery, as this can cause the unit to overheat
or ignite.
 Do not store battery in hot areas or throw it into fire. Otherwise, it
will cause explosion.
 Do not disassemble or refit the battery. Otherwise, it will cause liquid
leakage, overheating, explosion and ignition of the battery.
 Please store the battery in a cool dry place if you don't use it for a long
period.
 The battery can be recharged for hundreds of times, but it will eventually
wear out. When the operating time (talk time and standby time) is
noticeably shorter than normal, it is time to replace it with a new one.
 Please stop using the charger and battery when they are damaged
or show evidence of aging.
 Return the worn-out battery to the provider or dispose of it in accordance
with environment regulations. Do not dispose of it in household rubbish.
 Please use original batteries or batteries approved by the phone
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