I flip the switch on the back of mine to toggle from USB charging to light. USB port in the mount under the light grey weather cover.



I previously used a dedicated light and I was trying to build a USB charger with my soldering iron and electrical components. But when I went down hills I would blow out circuits, finally gave up and bought a new light/charger combination. At 25 mph with no load on the electrics, my hub would put out 34 volts AC.