Battery voltage when engine running
 

So I have noticed that on cold start and for a few minutes, my voltage is good (14.4v-14.6v) but after a few minutes of driving, it drops to around 12.0v - 12.5v and doesn't really come back up until the next cold start....

Is this a 'normal' MB thing, or is my alternator showing signs of wear? It seems quite consistent though like it is intended to behave like this....I've always understood charging systems to stay strong throughout, but perhaps I might learn something new here :nix: