Battery or Alternator?
 

I was driving today when my battery came on. Now, my car is only 3 years old, but I'm running an 800W and 400W amps in the back on my stock OEM battery. Also, when I get my revs high enough, the battery light goes off, but when I continue to drive, it comes back on. The car starts without a hitch, but my dashboard lights are a bit dim, even with my system off. Now, is it my battery that's not charging properly or could it be my alternator? I know, bring my battery to get checked, but I would like some input as to whether or not it could be the alternator. Thanks a lot guys!

sounds more like a problem with the alternator
Clip a volt meter onto the battery with the car off, you should get 12-13v then start it up and you should get around 14v. Rev the engine a little bit and it should stay steady around 14v

It could also be loose/bad connection somewhere. Check your engine grounds and the connections at the battery and alternator

monsoon is correct, but leave the multi meter on the battery for a minute while the car is running... if the voltage slowly drops your alternator is no good.

altenator.

make sure your belt is on tight too

wow altenator gone and its only a 03

Yes, I know, it's a bit odd, but I spoke with a few mechs and audio guys, and they each said that it's probably due to me running 2 amps without a capacitor, so it's really taxing the alternator itself, or something along those lines. But I got it replaced, changed my battery as well, so here's hoping less problems. Also looking into getting a cap as well...

it's probably to your 2 amps?

It's definately because of your two amps man.

Haha, yeah, I know :p