Elitegroup A900 (V2.1) - Manual (Page 46)

Battery Capacity Check Button
When the battery power reaches the "Battery Low Low" status or the
battery temperature reaches to a certain degree, a beeping sound will
accelerate. Save your work and turn off the DeskNote, or connect the
AC adapter.
Small Battery for the Real Time Clock
There is a small built-in battery that supplies power to the system in
order to maintain certain system information while the power is off.
WARNING:
Danger of explosion if the battery is incorrectly
replaced. Replace only with the same or equivalent type
recommended by the manufacturer. Dispose of used batteries
according to the manufacturer's instructions. Never remove the
battery pack wile the power is on as this may result in data loss when
the system loses power.
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