The electrical experts are all in violent agreement with one another
. Me: - I changed the spark plug leads and caps on The Duchess, my old R80RT, and went for a ride. I have been too busy enjoying the nice weather to play with the other pedants today.
The Duchess has an HID headlamp, which has a constant-current power supply that will operate quite happily from a supply at anywhere from 9V to 24V DC. The brightness does not change at idle, even though the voltmeter typically drops from around 13.4V to around 12.2V.
Same thing with my R1100GS. However, on my GTS, which has a different model of HID with higher output, the headlamp will sometimes dim very briefly (more like a flicker) when at idle and the brakes are applied.