Inspiron 5570 i7 8th generation, battery draining in 1.5 hrs

I bought my notebook last year, and it's not even a year and the battery does not last more than 1.5hrs in normal working condition (browsing the net and working on MS Word or Powerpoint. 

it's a Dell Inspiron 5570

i7 - 8th Gen

8gb ram

125 SSD and 2TB HDD

I have even tried setting up different power plans but it still does not work for me. I think there is some problem with the software.  my notebook is still under Warranty.

please help.