I did leave my head lights on about a week or so ago for about 5 hours while I was at work. I've driven my car every day since though, shouldn't the alternator have re-charged my battery completely by now? or does what i'm saying not make sense?
Ah, more clues. Telling the doctors everything makes it easier, ya know... ;)
Yes, it should have recharged by now, IF it were working properly. On the other hand, an alternator is NOT a battery charger, it's designed to merely top off whatever the starter depleted. Trying to use it to top off the effects of leaving headlights on for 5 hours shouldn't be that hard, but may have been the last straw if it was on its last legs. The alternator may now be working only partially-- not enough to keep up with a week of daily driving. If so, you're not going to see 13.8V when running, and yes, putting a battery charger on it for awhile should change the symptoms.