How can you make a larger current from a dynamo?

A dynamo is different than an alternator in the fact that the rotor is a fixed magnet rather than an electro magnet as used in an alternator. This makes a dynamo a constant output device. Usually the output is connected to a relay that opens when the battery is fully charged and the current is wasted. the only way increase output is to rewind the stator with more coils of wire. It is usually not possible to fit any more wire in the iron core of the stator as they are designed to be full at the designed output current rating.