This is completely unnecessary.
All batteries packs have a something called a battery protection circuit which is designed to disconnect the battery from the charging source once it reaches full capacity and disconnect from the load once it drops to a certain voltage. Below is a photo from a (circa 2007 MacBook) battery that has been disassembled.
When you overcharge a battery, you could damage it and cause it to burn. Without this protection circuit, at minimum you would be drastically shortening the life of your battery and at worst, starting a fire (thermal runaway).
There is an excellent YouTube video that shows how a protection circuit works through building one. There's also an excellent article on HowStuffWorks; Can your laptop battery be overcharged?