Charging system problem

[Infiltrate2000]

I have a brand new alternator in my car. My battery is about 6 months old. After 4 days of putting my alternator in, my battery died. Jumped it, and it starts. 3 Days later, it died again.
I tested my alternator today, at the alternator, it putting out 13.9v but at the terminal, it gets around 12.6. Is 12.6 enough to keep the battery charged? I am thinking it is because the battery stay charged for a couple of days. Some has said shorts but i drive my car everyday, if there is a short, it would happen every single day, not every 4 days or so. Any help would be appreciated.

 

[luv2rallye]

No, 12.6V is not enough to charge the battery (normal is 13.6-14.6V at 68 degrees F). You say at the alt you have 13.9V but at the battery + terminal it's 12.6V. I assume this is measured at the same time with the engine running. That tells me you either have a bad alt to battery cable, poor connection (corroded, dirty, not tight), and/or a partial short. Check these. For shorts see: http://www.dsmtuners.com/forums/showthread.php?p=1496998#post1496998 (do the in series 12V bulb trick to see if battery drain/short).

 

[Infiltrate2000]

i changed my battery last night. I now get 13.3v at idle. I will see if it dies again and then follow your tips.