So, coming home from work still without a single flicker after charging the battery last evening, I went and connected my voltmeter to the battery terminals. Steady 12.75 when not running. Idle without lights was the same, but at times undulating between 12,5 and 12,9. Switching the lights on dipped the voltage appr. 0,2 Volts, undulation as well. Steady 13,9 V at 3000 rpm, 14,2 at 4000 and up with lights on.
I think it's best to go and buy a small digital voltmeter and put it somewhere in the dashboard so I'd be able to watch the voltage when riding.