Bottom; Battery Pack - Asus N551J E-Manual

Bottom

NOTE: The bottom side may vary in appearance depending on model.
WARNING! The bottom of the Notebook PC can get warm to hot while in
use or while charging the battery pack. When working on your Notebook
PC, do not place it on surfaces that can block the vents.
IMPORTANT! Battery time varies by usage and by the specifications for
this Notebook PC. The battery pack cannot be disassembled.

Battery pack

The battery pack is automatically charged when your Notebook
PC is connected to a power source. When charged, the battery
pack supplies power to your Notebook PC.
Notebook PC E-Manual
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