Learnt thanks to English section of German product leaflet. This B&M Classic dynamo light simply days reverse polarity if running DC power to the AC dynamo light. I am setting it up on my Basman Project 346 Luna stretch cruiser with metal bottle friction dynamo.
That answers my desire for changing my e-bike headlight, on 2014 Bosch Performance Line that iirc supplies 6V DC (need to check it, I only measured my A2B Metro gen1.2 light feed i think).
It also means I can test the different dynamo lights on the ebike hopefully easier with more plug and play. The standard ebike light is an AXA iirc and decent straight path beam but i am hoping for the more natural feel of some peripheral lighting to remove the “night tunnel” feeling that detracts from dark night riding.
Ebike headlights from major suppliers are not common, so high power spotlight examples from China are the usual option.