battery light flickers on 2003 Ford Focus

My battery light flickers on and off at all different times. Never had an issue until I had the alternator replaced a week ago. I replaced the battery less than 2 months ago and when I had it tested it was reading at over 14. What could be causing this? It is the middle of winter and I don't want to get stuck somewhere. Every time I try to take it to a place like Auto Zone to have them check it the light is never on.

1 answer
Check that the battery connections and connections at the alternator are clean and tight. After that I suspect an internal alternator problem. Looking at the diode pattern on an an oscilloscope and looking at the pattern "loading" the alternator may show up the problem.