Don't disconnect the battery. You need to figure out why this light came on in the first place. Read the code from the computer. The connection is on the drivers side up by the fire wall. Get your book out on how to do this. It is pretty simple and should give you feedback in a few minutes. If you have a code the book does not have, bring that code back to the brickboard and someone will be able to tell you what it means. My car was having the same problem. I finally figured out what it was trying to tell me and I just replaced the alternator...

John