BattV issue - alternator?

[m4ff3w]

Are the problems shown below indicative of a failing alt (or Voltage regulator, but I believe it is internal).
The car will actually run rough at idle with the headlights on at times. Turn them off, and it idles OK again.

 

[racerx]

re: BattV issue - alternator

What voltage reading are you getting with lights on vs. lights off .use a digital volt meter for this test? If it drop a half volt or less its ok 2 or 3 volts not as good. Put a known working battery on cheek voltage. Take your old battery out when doing this test.