When you’re away from home and your cellphone runs out of juice it can be a real downer. Sure, you could find a store and buy a wall charger, but wouldn’t it be more fun to build your own battery booster without using tools? [Spiritplumber] did just that, popping into a Radio Shack for the parts, then making his how-to video (embedded after the break) while standing at the checkout counter. You can see he hust set his camera on top of the battery display case and got to work.
He’s using four D cell batteries to provide 6 volts of power. Assuming your phone charges at 5 volts this is going to be just a bit too high, even though there’s some tolerance with most phones. To overcome that obstacle he added a diode to the circuit, taking advantage of the 0.7 volt drop that it brings to the mix. Grab a plug adapter for your model and then just hand twist the connections. [Spiritplumber] admits it would be better to solder these, but in a bind you can get away with it. We looked up some prices for this method and we figure this would cost around $18 (batteries included) depending on the price of the plug adapter for your phone.
Of course if you’re just looking for a way to charge your phone without paying consumer prices there are ways of accomplishing that as well.