Boston Stenny

ok i am usually pretty good at figuring out and fixing problems with cars and trucks but i can't get this to work right. i have changed starter, alternator, and battery. i also ran a new wire from battery to alternator thick wire that goes to battery. so i run truck it runs ok then i shut it off and battery won't have enough of a charge to start again. now i put a new battery which is 800 cca in yesterday, along with a new alternator. i just can't figure out what is wrong. i figure someone may have a test or may know what could be going on here.