Google translates the important bits as
"The device itself is at first sight only from cable, the mini-USB connector, three brass tubes for connection to the rest of the bike electrics and a switch. The actual charging electronics with green status LED is hidden in a piece of heat shrink tubing in the middle of the cable. The shrink tube with adhesive filling ensures a watertight seal of the electronics. The total weight is 27 grams with a sensational low. Because it is so easy, can be dispensed with an elaborate fortification. Of delivery are a couple of cable ties in the assembly. It works. But not everyone will want it, allow the unit to constantly on the bike.
Switch and connection are designed to manually switch between light operation and charging. Feasible but is also a separate connection to parallel to the light system with the option, switch the charger from the lighting system.
When operating without loads connected to the hub dynamo is already at a comfortable ride that the electronics are pretty hot. This is due to Zener diodes, which limit the input voltage to approximately 15 volts to protect the switching regulator. If the temperature exceeds a certain level, a protection circuit, the device completely. The green "Power Good" LED turns off for a few seconds. With connected consumers have to be relatively sporty way to feel a significant warming."
Looks like a neat solution at €39