Science Buddies: "Ask an Expert"

There is a black out and all of your devices have gone dead. Build a device using household materials (except preconstructed motors and battaries) to charge your smartphone.
i have done research and tried alot of experimenting but i cant seem to build anything that would give enough power to charge a smartphone.

it's not a good idea to cobble together power supplies that aren't regulated unless you want to fry your cellphone, but you can just make batteries out of acidic fruit and different metals, or stack nickels and pennies together with paper towel soaked in salt water. You need a lot of fruit or pocket change though.

http://www.thenakedscientists.com/HTML/ ... th-lemons/

It's a bad idea and you'll likely damage your phone if you manage to get it to charge at all, but that's how I'd do it if I wanted to. You may need to do a bit more experimenting and I'd suggest you have a meter handy to check voltages & current, and experiment with an old phone you don't care about.