Theres an Easy way to figure this one out. Take the starter out and a proven-good battery and test it by placing the ground on the body and the positive on the lead-in terminal. If it flings free and easy, chances are its not the starter. However, if the starter heats up, or the wires get hot, theres resistance inside the starter motor. Finally, the easiest way to see if your battery is good is replace it for a few minutes with a good one. If it turns over with no problem, the batterys the culprit. However, dont rule out the positive lead to the starter solonoid. You replaced the battery terminal, but did you replace the 2nd half?