hi i was just wondering: if my macbook is plugged in then does it use the battery power while it simultaneously charges it? or does it directly use power from the plugged in power source and not use the battery at all. i was wondering cause i read a lot of threads where if you use your macbook battery for a certain number of cycles the battery life goes down dramatically. i was hoping that if for the majority of my ownership i have it plugged in i could avoid this problem. thanks for any replies!