Battery Light?

was drivin home last night and the battery light came on, stayed on till i got home (like 15 mins) than this morning when i started it (it started fine) the light was still in and stayed on for about 45 mins and now it's off. It's starting fine, any idea's what could have happened, i havent had any battery problems before, i don't use sub woofers or anything.

OH MY F'ING GOD, well i found out why the late had come on. so I'm drivin to pick up a friend prolly about 10 miles away from my house, I step-on the gas it kinda like sputtered/ the light flashed on again and stayed on and i smelt a weird smell. I pull over and the wires connecting to the alternator are on fire. I blew them out, so ya the plastic that the connects the wires to the alternator is just melted, the wires and melted. So i taped up the wires and drove home and now it's parked here. Gonna have to go buy a new alternator and see if I can get the wires from pick n pull or somethin. I can't believe this ****.