1999 Holden Calais

Engine Performance problem
1999 Holden Calais V8 Automatic

I've had this problem for 2wks now hopeing it was the battery. The battery is fully charged, go to start car and all I get is a click click sound, it wants to start but dies down to just cliciking noise. Not sure if its the alternator, solinoid, or starter motor. I'll be driving for at least 20ks then battery light on dash board will come on for at least 3mins, then switch off, and back on again, then the dashboard lights will start going haywire and start flashing, then repeats the cycle again. What are my symptoms? Or what should I be looking at repairing first.
May 26, 2010.

Get the battery and alternator load tested

May 26, 2010.