You could also just have a bad connection somewhere in your system. I had a 71 Challenger. It would actually cook the battery. I chased all the wires under the hood and the dash. Finally one day I was laying under the dash just looking around and saw a black streak in the connector for the steering column to the main harness. It was the main (heavy) red wire. The connection was bad. I snipped the wire off on both sides and used a "butt" connector to make the connection. Solved my problem. Charging went back to normal.

Look at all your connections. Pull them apart. I could not pull that one apart. I was lucky it didn't burn the harness up.