Transfer from Singapore to Tokyo at Beijing Capital Airport

Hi I need to transit using AC from Singapore to Tokyo. It said that the arrival terminal and departure terminal will be at T3. Based on you article above, I don't need to go through immigration is it?

But do I need to take my checked-in luggage?

Some more, will there be any issues if I put my power bank to checked-in luggage? Or is it better to put it in hand carry bag? Thanks