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Hi! I would like to make a hand crank cell phone charger....

Hi everybody, How would I make a hand crank cell phone charger from scratch (meaning, not just taking a hand crank flashlight and rigging it to charge a phone). I would really like to understand the electronics behind it all. I think this would be extremely useful if my phone died and I had no outlet available. I know I'd have to use a small motor, but how many volts? amps? etc. Thank you so much! patti :)

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csh267 years ago
I was just watching a video on youtube recently about that. Here it is.
orksecurity7 years ago
It will take a fairly obscene amount of cranking; cell phones draw a lot of juice. For comparison: Fifteen minutes of cranking on a commercially-made (Eton) emergency light/radio/phone-charger may only charge a phone enough to make a one-minute call, according to the user's manual. If that doesn't put you off: The motor acts as a generator, hopefully producing a voltage higher than needed to charge the phone -- if not, you need to put it through a transformer to get that higher voltage, at the cost of losing some power. The voltage is then rectified and put through a regulator circuit to smooth it out (typically at 5V, for USB-charged phones), and you then hook that up to the phone as usual. Theoretically any permanent-magnet motor can be used as a somewhat inefficient generator; the differences are in how fast you'd have to crank it to get a given amount of voltage out and how quickly you'd destroy the motor in the process.
mckywer (author)  orksecurity7 years ago
Wow - a lot of work it seems like, but awesome. Thanks for the answer - VERY informative!!!
jj377 years ago
as for the volts check the back of your phone battery
mckywer (author)  jj377 years ago
thank you!