As additional light quite well

For the price you can naturally expect a high quality product.
But for the winter time as additional lighting, especially if the Dynamo again fails adequately.
It is true that no StVZO, but if you set continuous lighting, instead of the flashing functions, security is enough done.
The holder can be relatively simple and well secure. What I can not say looks at consumption.
But this is likely to be also dependent on the quality of the batteries and temperatures.