Chevrolet: electrical problems, 350ci, charging system

Question
i've recently bought a 442 with a chevrolet 350ci in it. Approx. 2 weeks ago i left the car at a shop for a week and got it back and the battery was dead so i got a jump got to my destination and returned to my car and it wouldn't even turn over. So i ran new wires under the hood replaced the altenator yesterday and the car still would turn over tested my battery, it was dead put in a brand new one and it fired right up so i came to school its about a 15 mile ride from where i live and i cut the car off and just to check i cut it back on to see if my problem was solved and the car began to turn over but its not enough juice to start the car if possible please give me an idea of where to start or what the problem could be thank you

Answer
Dante;
 Hea- well it sounds as if you have a poor charging system,
you will end up with the new battery dead. I would get a meter and see what the alt. is putting out. also if the battery is getting over 13+ volts charge.    do you have any acc. that might be running when you turn the car off, raido, stereo fuel pump? its draining or its not charging.  ok
Roger