Reddit mentions of HUABAN Hand Crank Generator High Power Charger for Outdoor Mobile Phone Computer Charging 30W / 0-28V with USB Plug (Green Generator + DC Regulator)

The thing is, this waterlily actually does work about as good as you could expect something this size to work, the problem is that it doesn't do enough. The storage capacity of say, your iphone's battery at ~3,000 mAh is barely budged with the piddly output of the waterlily. It will eventually charge a phone battery given enough time but that time is impractical.


It's easy to understand the principals at work here, turbine generates electricity, make it small and compact and you can charge your phone on the go. It's easy to trick yourself into thinking this should or could work. The problem is the vast difference in scale of what a portable turbine can do compared to the incredibly power dense batteries we carry around. So it really isn't very close.


Even the hand crank on this thing is useless because the turbine is geared to move at even a light breeze, which means your cranking doesn't require much force, which mean not very much work is being captured which means you have to crank it a million times to get anything useful out of it.


For an idea of what is realistic,check out a hand crank like this. You strap it to a tree and crank the thing which has a fair bit of resistance at a pace of about 80-90 rpms consistently for a half hour and you can maybe expect 10-15% of your phone's battery to charge off of that.