Long time ago QVC sold a shakeable Flashlight that had no batteries just a shakeable generator and a super capacitor. This flashlight uses a 5vdc 1.5a wall wart to charge the capacitors. To figure out how long it will take to charge the flashlight you use this equation $$T=5R_{currentlimit}C$$ And for total discharge time $$T=5R_{LED}C$$ …
