How to Make a DIY Car USB Charger

USB (Universal Serial Bus) has become a standard for not only computers, but for most gadgets and electronics, which have USB cables that allow them to either connect to or simply charge from a computer. The same USB cables and ports can charge a wealth of devices. However, travelers and drivers don't always have access to USB ports on the road. But an electronics hobbyist can easily whip together a simple USB car charger.

Old Materials

If you have a car charger for an old cell phone, and any female USB cord, you may think you have already got most of the materials for the charger. However, it's not necessarily that simple. Make sure the old car charger puts out exactly 5 volts (V) at 500 miliamps (mA), because that's the standard voltage and amperage for USB devices. Any higher or lower, and you risk burning out or damaging the device in question.

If you don't have a female USB cable, you could use a USB port from an old computer. You will need to take care to ensure you don't damage the board you're removing the port from. If you're taking the part from a cable, you only really need the USB port end.

Testing the Car Charger

If you have an old car charger and aren't sure whether its voltage and amperage are correct, look on the transformer end of the cable for a sticker or some embossed text. Most chargers will have the current information printed on them. If there is no sticker, use a multimeter to check these measurements. Plug the charger into the car's lighter port and use the multimeter's leads to verify the electrical current. Once again, it needs to be exactly 5 volts at 500 miliamps. If the charger doesn't meet those criteria, you will need to find a different one.

USB Ports

If you look into the female end of the USB cord, you will see four contacts. Hold the port so that the contacts point downward. The charge comes from the first and fourth, which are the outermost contacts. When attached to a computer, the inner two are used for data transfer. When putting the charger together, connect the positive wire (usually the red one) to the back of the USB at contact 1 and the negative (usually black) to contact 4. Soldering is the best way to ensure the contacts work.

Aesthetics

While putting this together is fairly simple, you may want to take a few seconds to make the cable look nice. Electrical tape that matches the old phone charger looks convincing enough. If you have a little extra time, you can use a heat-shrink tube to give it a much more finished look. Be sure to slide it on before you attach the USB end of the cable, however, or you will have a hard time adding it later.

References

• How to build a USB Car Charger: Modd3d