How to Make Your Own Battery-Powered Gadget Chargers

With a few AA batteries and $5 worth of parts, anybody can cobble together an emergency cell phone charger. Here's how to do it, and how to extend your charger-building skills to work on digital cameras, laptops and even power tools.

There’s no magic to a cell phone charger. It’s really little more than a plastic-wrapped strip of copper wire designed to deliver power (stepped down in voltage and converted to DC, of course) from an outlet to your phone battery.

So if an emergency strikes and you find yourself without either your charger or a working wall outlet, it’s really pretty easy to MacGyver together a contraption that uses AA batteries to quickly give your phone enough juice to make a few emergency calls. The whole process, which is a lot like a miniature version of jump-starting a car, takes minutes and uses parts that can be found at Radio Shack for less than $5.

To do it yourself, you’ll need the following: a few AA batteries, a four-AA-battery tray, a metal paper clip and two alligator clips. That’s it, and the finished product should be able to charge just about any phone (with the notable exception of the iPhone, which does not have an easily removable battery) if you find yourself in the wilderness or waiting out a power outage.

Check the voltage

The first step is to check the voltage on your phone battery. Most clock in at about 3.7 volts, but you should pop it out of the phone and read the fine print to see for sure. This information will let you calculate how many AA batteries you need. The key is to use enough to barely exceed the phone battery’s voltage. Employ fewer and you won’t be producing enough juice to charge the battery, but hook up too many and you could burn out the whole thing. AA batteries are 1.5 volts each, so charging a 3.7-volt battery requires combining three of them for a total of 4.5 volts.