Nexus One - Artwizz charger not okay?

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I've bought a AC Charger for my Hero. It works fine.
Now I took it to load my nexus. With this charger, the Battery is in 4 hrs full!!

I looked at the screen and it says: Charging over USB. With Stock Hero Charger there is "Charging with AC Adapter"

Could anybody tell me, whats wrong? why can't this load correct?

It's this from Artwizz:
http://www.artwizz.de/product_info.p...PowerPlug.html

same here, i think there have to be a certain voltage on the data pins.