You probably know your battery is best served by shallow discharges and regular top-offs, but calibrating your battery occasionally is important too—otherwise the display that shows you how much charge is remaining can be wildly inaccurate.
If you've ever seen your battery zoom from half-full to near empty in what seems like an instant, or plugged in your charger and then unplugged it only to see what you thought was 100% is really only 95%, your phone or laptop battery may not be reporting the correct charge—which means it may not be properly calibrated. Over at How-To Geek, Chris Hoffman explains that regular top-offs are important, but a good calibration is important too:
We'd suggest making it part of your regular PC cleaning ritual, maybe every year in the spring, or every six months or so. Calibrating your laptop battery isn't hard—it's essentially the process of running your battery down to near-empty and then charging it all the way back up to full, and some PC manufacturers even have utilities that will do this for you. If you'd prefer to do it manually, the full post linked below will explain how to do it. (Note: If you own a Macbook made in the past few years, Apple says you don't need to worry about calibration at all, as OS X handles it for you.)
Reposted from Lifehacker.com