Originally Posted by Adamphl
no, that's entirely wrong oswald. draining the batteries actually harms them. lion batteries perform best when receiving "small" discharge-charge cycles.
Actually, completely draining the "smart" li-ion batteries once in a while (say once a month or two) has one positive effect - it recalibrates it and keeps the "charge level" indicator in Windows accurate. I have experienced this on several batteries used on Latitude CPX, C610, D600, D800, Inspiron 8000/8100/8600 that I've used personally and at work. I have noticed that as the batteries got older, they would jump down from about 20%-10% to 3% in a matter of several seconds and hibernate somewhat unexpectedly. Eventhough I have set Windows to hibernate at 3% battery level, I did not expect it to jump down from 15%/10% to 3% in such a short time span. However, the batteries recalibrate themselves if you drain them completely. To drain completely, turn it on and go to the BIOS(setup) leave it on until it dies. However, like the gentleman said above, don't do this very often as it could shorten the overall life of your battery.
Although I don't have scientific measurements to support this, in my experience, rapid discharge cycles shortens long term battery life as well (probably due to the heat generated). So, try to keep your notebooks plugged in when gaming or other high power demand activities.