1996 Chrysler Van my car doesnt wanna start some times

i used battery tester in shop ..its said battery and alt also i replace them both,,,everything was ok when i got home and at morning it didnt start i jump it to get my work i put the battery on charge and then i test it ,,it's said battery and alt again ...i order new battery and alt again i put'm in car 2 days after ,,same problem again ..it didint wanna start ....its drive crazy this car...what you think guys the real problem????