Battery

I have Dell inspiron 7567 and lately my laptop battery just died. So i got the replacement of the battery which is fully functional and picks up as a DELL genuine battery with samsung SDI being the manufacturer. So what happened that whenever i charge the battery it never go past 70% and stays between 60-70%(I use my laptop in High performance mode and battery used to lasts around 3hr in 100%), and 70% gives me around 2hr of battery back up but also when windows battery indicator hits 0%, the laptop is still fully functional for like 1hr which accumulates the remaining 30% of the battery (which i dont know why windows or bios or anything doesnt want to pick it up). Does anyone know how to resolve it? aint a big deal but it still annoys me. I did that 15-30 second power button trick(nothing happened) and i drained the laptop battery twice now and started charging from dead 0(the state laptop doesnt want to turn it on.)(nothing happened) Please help me.