Typically in bicycle dynamos the current is limited by internal impedance. A bike dynamo typically seems to top out in the .6 Amp range maximum regardless of the voltage reached. Above minimum speed pretty much a constant current source.
At higher speeds the voltage on an unregulated unit can get quite high but the current is self limiting per graphs I have seen. Some lights such as the Supernova E3 Triple use this to draw more total power. Per an email I received from Supernova the Triple does not reach full light output until about 25 MPH when run off of a hub dynamo. I suspect that it would never reach full output if run off of a bottle dynamo such as the Dymotec 6.
Again per the graphs I have seen a 3 watt rated bottle dynamo can reach about 6 to 7 watts maximum actual power out while a hub dynamo can get closer to 12 to 14 watts out. Of course the input to achieve this hs to come from the rider.
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Gear Hubs Owned: Rohloff disc brake, SRAM iM9 disc brake, SRAM P5 freewheel, Sachs Torpedo 3 speed freewheel, NuVinci CVT, Shimano Alfine SG S-501, Sturmey Archer S5-2 Alloy. Other: 83 Colnago Super Record, Univega Via De Oro
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