Joined: Jan 2009
Posts: 44,338
Likes: 6,637
From: New York, NY, and High Falls, NY, USA
Bikes: 1962 Rudge Sports, 1971 Raleigh Super Course, 1971 Raleigh Pro Track, 1974 Raleigh International, 1975 Viscount Fixie, 1982 McLean, 1996 Lemond (Ti), 2002 Burley Zydeco tandem
A dynamo hub produces about 3 watts, maybe more. That's not enough to charge even an iPad, much less a laptop. An iPad needs about 10 watts. And that's not even getting into conditioning the current and converting it to the proper voltage, which will reduce the amount of available power.