You're a road warrior-complete with laptop, but your cell phone is running out of power. You need it on, but there's not a power outlet in sight. What do you do? In the post-K750i era, most phones will charge off their USB cables, but fret not if you have an older phone-if you've got a charger and USB cable to spare, you can make your own in 15 minutes! The method works with most phones that have a 3.6 Volt Li-ion battery (this is usually mentioned on the battery itself), but still may not work with some, so make sure it's a spare charger you're using. We've used a Sony Ericsson K508 for this, but most phones will do-there are supposedly cell phones out there that wouldn't work-requiring greater current than the USB port can deliver-but these should be very few, and you'd be really unlucky to have ended up with one.
1. Know Thy USB
The two extremes (pins 4 and 1from left to right) are the ones we're after-they're the negative and positive terminals for USB power respectively. Pins 2 and 3 are for data.
2. Hack 'Em Up
Use a wire cutter or just a blade to cut and open up both the charger and USB cable. The red and black wires in the USB cable are what we're concerned with-the white and green are for data, so don't bother with those. Your charger should have red and black wires too-we know of none that wouldn't have the colour-coding, but you never know.
3. Making Ends Meet
You've probably guessed this now-join the two red wires and the two black wires. If you have access to one, use a soldering iron and secure the connections using solder. This will keep it intact even if you use it a bit roughly. Insulate them from each other using electrical tape (extremely important), and you're done!
Voila! It works! The next time you have a battery emergency, just leech power off your laptop and make that all-important call!