Is it draining the battery or overcharging it!!! Check the output at the alternator, and see if you have a short somewhere that is draining the battery.... Most parts stores have an inductive amp gauge that they can check the amperage output of the alternator. A simple check to see if you have something draing the battery is to have the key off, then remove the negative cable, when you get the negative cable almost to the negative battery post, is there a spark? If there is, you have something draining the battery.