Full Charged Capacity E7470

Hi, i bought this laptop a few days ago used, and i had no problem with it, except from battery. The first day the battery showed its condition as "Excellent" but now its says "Fair" so i checked it with the html report and each day it was losing 2000mWh of its full charged capacity. It also drops from 30 to 7%. I already tried to manually calibrate the battery but nothing solved, i even lose like 4000mWh from the process. My question is, if i replace it will be solved? because maybe theres some problem with the pc and not the battery, maybe the new one its gonna do the same. (Sorry for my english).
Ask me if u guys need anything else.

Thanks!!