Typically, all notebook batteries are built to handle a certain number of usage cycles, around 500, and often more. Each cycle of use decreases the battery’s capacity, so the less you drain it, the longer it’ll last.
If you leave your battery plugged in for long time it will cause heating issue. Letting a battery charge to 100 percent all the time does tend to wear the battery out more quickly, while letting it fall too lower in the other direction too often can also be bad news. The happy middle ground is, according to Battery University funder and Cadex Electronics CEO Isidor Buchmann, is somewhere between 40 percent and 80 percent battery life.
So the best thing you can do for your battery is charge when it reaches 40 percent, and unplug it when it goes past 80 percent.
Read more: http://www.digitaltrends.com/computing/how-to-care-for-your-laptops-battery/#ixzz3mzxbc073