Im also dealing with this issue. I replaced my battery and 2 days later, battery died at my college. Get a 20 min. charger to get home, Alternator picked up slack until i got home. Ended up taking the alternator out of the van earlier today and got it tested at autozone. Alternator passed all 3 tests. Battery was a bad battery again. So I got another one. Put the alternator on with new battery, drove for 20 mins. to see if it was fine. After getting gas, the battery light and brake light kept going on and off at random times until i got home. Before i went on test drive, the battery was at 12.88V while out of car. On start up, jumped and stayed at 14.4V. i rechecked at home and ot dropped to 12.68V. I actually don't have any clue why this is happening if my alternator is fine. Also checked the connecters and grounds and Alternator relay. All seemed fine. Didn't check the fuses on the positive battery cable. I'm in automotive classes at my college so I'm going to ask my instructers tomorrow to see if they can shed some light on this trippy K.I.A.