I changed my alternator. But I dont know if its bad or not. Its daytime now. So I cant recall dim lights . But , when I remove my POS cable while the car is running, the car dies. Futher, the battery is slowly losing its charge after each use. The terminals are changed and clean. I changed those too. When I changed the alternator, it charged up the battery and the battery light went off, for about a half an hour, then started loosing charge again, and the battery light went back on. Initially It started out by the battery light coming on when the RPM"s were increased. Im confused.

Optional Information:
1998 Ford Ranger 4.0

Already Tried:
Changed the alternator, changed the Neg terminal, cleaned the pos terminal. Wiggled the wires. Recharged the battery at the Kragen store. They didnt tell me if it was bad or not though. I will find out in a few minutes. PUlled the POS cable while the car was running and the car died.