Originally Posted by KC8QVO

Dyno hubs run around 6v AC. That, and they produce so little power. I'd say the vast majority are under 10 watts - at 6v. As soon as you transform that voltage (you can do so with a step up transformer, for example) you loose so much power in the transformation process you only have a couple of watts left.

That reason is why I don't yet have a dyno hub on any of my bikes. I have a 17+w solar set up that I charge a 12v battery from when I stop on my long rides. The battery is not used for drive, only powering accessories.

Back to my edited comment in my last post, also - E-bike drive systems can get up pretty high in voltage, also (48v on some, I'm sure there are a lot of other voltages). The larger the difference in input voltage and output voltage, in a step up transformation, the less efficient the transformation is.