The incident that occured with laptop being left with charger is an unfortunate one. But also, i would say that its an isolated one. Thing about Li-ion batteries used in todays laptop are that they are controlled by smart circuit. Every battery has a charge bit assigned to it.Usually when your laptop battery is <95% the bit is set to 0. This tells the charging circuit on laptop to charge the battery. once the battery is again charged back to 100%, the charge bit is set to 1. This tell laptop to stop charging. This bit remains 1 until battery level falls below 95- 97%. Yes, even if your battery shows 100% , it can be at 95%- 97% and still wont charge. This safeguards the battery to prevent charging of battery all the time and also prevents over charging. in short, you can think of this as an auto charging cut off feature. Its been there since long time in laptops. If you want to check for it, leave your computer shut down, connect power adaptor and leave it there for 3 days or more if you like. check periodically and you will see that whole laptop will be cold as steel. No overchaging. besides, try this on your phone and see how hot it becomes. That is over charging. so you dont have to worry about it. Plus, most of the internal batteries that come in high end laptops are called smart batteries . they have this protection built right into them and they dont have to rely on your laptop circuit to protect from over charging and such.
