I have been running my mac on the AC cord today, I had been doing some photoshop stuff on it, then I shut down photoshop. I left the room for about 1/2 to an hour, I come back & sit at my computer & see the charger light is orange for charging, notice my battery was at 7%. I did not unplug from the AC today, & the magnetic end of the cord had not come out, the last time I looked it was at 100% charge, at least the last time I remember for yesterday. I usually run off battery to about 90-70% to keep the electrons moving per instructions for notebook batteries from apple. But I had not unplugged & run off battery today.