I lost the wallwart charger for my Motorola V188 cellphone.
So I made a USB->cellphonepower cable and now I charge my phone from my computer's USB port.
This is all a bit ironic, because the phone already has a USB port on it, but is only for data.
It can't charge the phone due to evil suits needing to sell overpriced wallwarts.
WARNING: you probably want to put a fuse in series with the +5V wire and be somewhat careful so you don't fry your computer or cellphone if you accidentally short something.
Step 1: Wire It Together
I happened to have a dead cigarette-lighter-charger with the right power connector on it. I cut that wire and stripped the wire ends.
I cut a USB cable in half and stripped the red and black wires out of that. They are thicker than the others. Black is ground, Red is +5 volts.
I connected red to red and "other" to black. Be somewhat careful, you don't want to toast your computer. I covered my bare wires with packing tape. I didn't have any solder handy.
I plugged my phone in and it charges just fine.
I've been using this setup for a couple of weeks now.
The original charger supplied 6 volts to the phone. Only. The battery management circuitry is all built into the phone.
The battery in the phone is only 3.2 volts, so I figured 5 volts from a USB port would work.
It works fine. Eventually I'll solder and clean up the wiring like this.