It will be very slow as the USB power output standard is not large.. and you have to be moving . (Bring your Mains Chargers too)
Tablet battery may take days of riding..& may never catch up .. so ask to plug in while having a nice luncheon ..

The Plug III and The https://www.sinewavecycles.com/produ...cycles-reactor are competing products offering the same idea.


Last year a touring cyclist, as many do, left their bike for boxing and shipping back @ the LBS..
She had a German Made wired head & Tail light which does not blink,

and a USB internal battery one that did blink, and a power cord running up to it..




....