[GTP Dad]

There are a couple of ways to check the battery. If you have an inexpensive volt meter check across the terminals. You should read at least 12 volts. If you have less than that you will need to recharge the battery. As far as the battery light coming on when you have the CD on, do you have a set of base speakers? If you do you may be draining too much power from the battery while using the CD. If not you could have a short in the CD player that is causing an extra drain on the battery. There is an easy way to check the alternator to see if it is charging. I would suggest that you recharge the battery and check the belt. If the belt is worn and slipping replace it. If not then you need to check for a short in the CD player. If nothing is found check the grounds on the remainder of the car to make sure they are good. Also check the battery terminals and make sure they are clean this can cause the battery not to take a charge from the alternator. Hope this helps!