[P11GT]

I was wondering if anyone has come across the same problem.

Basically, the cars running two amp system off the original battery, and at night, when the cars running and the headlight are on, i can notice the beam of light flickering ever so slightly. Its more noticeable at idle. When i rev the engine, the light beam is brighter, but there still is flickering going on. Ive tried switch off all uneccessary electronics, like the sound system, heaters etc, but it still happens. I believe the battery is in good general condition as i tested it not so long ago, and the altenator to be working fine, as the battery light doesnt come on when im driving. Can anyone shed some 'Light' on this matter?