Aygo Headlights Dimming with Aircon

[MikeB444]

I was temporarily car less today so borrowed my son's Aygo (2011 vintage) to get to work.

When on full beam the lights seemed to dim a little when the aircon kicked in.

Is this an indication of something not quite performing (alternator???) or is it normal for the Aygo.

I did put some new Osram nightbreaker silvers in it a while back. I don't think they draw any abnormal levels of power though.