Its mentioned there that one should start charging as soon the battery reaches 20%.
If one uses battery care option ,the battery charges for upto 80 % there by eliminating overcharging which usually occurs after 100%.
This function was there in my previous laptop Sony vaio. believe me it did no good.
I just lived with 80 percent of charge all my life while i used it.
3 years it ran on same 80percent function and later when i tried the to utilize 100 percent it delivered only 1.5 hours.
with my electronic knowlledge the biggest enemy of battery is heat , sulphation(or ionisation) and overcharge.
1. Never let batteries overheat anything more than 35 degree is detrimental to battery pack gases inside expands and it start to leak and such anomalies and aggressive chemical reactions et al.
2.Ionisation - long time storage without charging will commence corrosion inside which is a slow poison.
3.Overcharge- i think most of the present day technology is equiped with overcharge prevention technique which allows batteries to be charged upto 95-97 percent only. so 80 percent theory is kind of redundnt here.
4. Do not unplug or plug the charger when it is charging .Either you switch off the PC or wait until it gets 100 percent charged.
ps:- Accidents cannot be avoided always , a voltage spike can prematurely kill battery . so try not to plug in anywhere you find sockets like airports,cafes , etc.