Black Market iPhone Charger

Note: most of this post was written months ago. Since I'm getting more and more into electronics tinkering, I decided to finish it up and publish it.

Have you ever tried to charge your iPod or iPhone with something other than the included charging cable? Then you might have seen this dreaded message:

How does it know? What's special about the Apple USB charger? Doesn't the U in USB mean Universal? Well, yes it does. But for some reason Apple doesn't want just anyone making (or making money from) an iPod/iPhone charger. That's why recent versions of their products don't work with any old charger.

Well fuck them.

Actually, I really like Apple and their products, except for the "non user-serviceable" attitude they have. You can't swap your own battery. You can't modify the hardware in any way without voiding the warranty. Well, I never use warranties anyways.

So here's the deal. I needed a charger for my car. I already have a 5V power supply that is providing in excess of 1A. I just need to be able to put the iPhone into high amperage charging mode and trick it into thinking there is a legit Apple charger doing the charging. The way to do this is kind of sneaky.

USB has only 4 wires. Two for power (a 5V and a ground) and two for data (D- and D+). With any standard USB device, you should just be able to power it with the two power wires. You can leave the data wires unattached.

But with a newer Apple device, if there is nothing on the data wires, then nothing happens! It won't charge! The power is there on the power wires, but your stuck up little iPhone scoffs at it. It can tell that you are using a non-Apple charger because Apple chargers sneakily put a small charge on the data wires.

To fake an Apple-supported wall charger, put 2.0V on D- and 2.8V on D+. To fake an Apple-supported computer charger, put 2.0V on both the D- and D+ wires. The distinction here is that the wall-charger will draw a full amp or more, whereas the computer charger will only draw half an amp, to adhere to the USB spec.

So I went to Fry's to get some resistors and a female USB port and was in business.

Materials used
- 24 hour fitness membership card
- 2x 51K Ohm resistors
- 1x 47K Ohm resistor
- 1x 75K Ohm resistor
- solder
- electrical tape
- female port from a usb extender
- wire

Tools used
- drill
- soldering iron
- wire cutters/strippers
- voltmeter
- The Internet

First, I drew out a schematic. It's not very complex, but it was fun flashing back to high school AP physics!

Then I drilled a bunch of holes into my 24 hour fitness card and started soldering and taping. Here's the finished product:

This is now tucked away behind my dashboard, powering my iPhone every time I plug it in, without having to buy a special charging cable.

USB connector pinout
iPhone dock connector pinout
Resistors on the D-/D+ USB pins for iPhone
MintyBoost! (provided much background information for these types of hacks)
MintyBoost! video teardown of charger
Resistor band color guide
Apple's own documentation regarding power through USB