thank you for the replies
It is the FI version, bought here in Europe, I have no idea what power the stator is and unfortunately the importer is not as helpful as CSC. But it is slightly face-lifted version, already coming with USB and cigarette lighter plug. So maybe, just maybe it's 300W
Anyway I'll plug the lightbar I have on the car into the circuit and measure the voltage on the running engine, as per @Working_ZS suggestion. It is drawing around 6.5A @ ~14V (measured on the car) so it'll give me an answer on what can I purchase for the bike