budweiser.junky

hello all. having an ongoing problem with my zj, it keeps killing my battery. i have gone through 3 batteries but when i took my alternator to autozone to get it checked out, they said it was in good working order so i had them check it twice to be on the safe side. nothing in the zj stays on and i even unplugged the sound system and the alarm system. i did however notice this morning as i was coming home when i was at a stop light the charge gauge was very low. any ideas, any and all help is much appreciated.