You can get 14+V at the battery posts with a good alternator and a marginal battery. What do you get an hour after the car has sat idle? What do you get when cranking?

Your alternator can charge even without the exciter wire being hooked up (the little red wire at the alt that is ultimately connected to the bulb in the dash). There is residual magnetism in the alternator that once it reaches X speed will self-excite (I always feel dirty typing that) the field coil and once it is excited it stays that way (again, I feel like a Viagra commercial).

You can read all about my soapbox item, the alternator ground wire, but I will just say that it is the most often overlooked cause of intermittent charging issues. There is not reasonable way to inspect it on the car but if you must, pull hard on the wire as if you are trying to pull the end off. Do it in both directions so that you test both ends. Then insure a clean tight grounding point where the chassis-side eyelet connector is bolted. By that point you might as well have removed it and inspected it off the car.

Mike