I'm using 2010 MBP and now it seems at the most I can get from a single charge is 2-3 hours of use. I want to know if there is way to know health of battery as well as if I need to get it replaced ? Within 2 years of use the battery drain feels bit more unusual but is there a way I could calibrate it or improve it ? Most of time is it simply web surfing and light weight computing.