Right, but surely there is some level of use that is not high enough to make the USB charging necessary, right? I plan to use mine 1-2 hours for fitness a week, I expect it will replenish that from the solar panel alone.
It's not clear. It's possible that even if you don't use the fitness at all, you'd still have to plug in once a month. Or maybe your situation would work, i.e. it could regenerate an hour worth over the span of a week.