Cell phone charger. Works...and doesn't...

[bigone5500]

I just built a cell phone charging pack using 4 NiMh 2000mAh batteries. I connected them to the USB cable through a 7805 regulator. Works like a champ on my android phones but when I connect it to my daughter's iphone, it says the device may not be supported.

Wiring is like this:
Black wires from the batteries and USB are on pin 2 of reg.
red wire from USB is on pin 3 of reg.
red wire from batteries is on pin 1 of reg.
Green and white wires are connected together and soldered.

What could I do to get this to work with iphones?

 

[(*steve*)]

For an iPhone you need to encode some "values" on the other 2 pins. Without these, the iPhone won't know how much power it can draw.

You do this with resistors or voltage dividers.

 

[bigone5500]

What values are needed to allow 500 MA charging?

 

[davenn]

What values are needed to allow 500 MA charging?

some google searching on chargers for IPhones will probably get you the info

Dave

 

[bigone5500]

Ok. I have done some research and found the resistor values needed. I have the D+ and D- voltages to within .5v. When I plug the iphone into the charger, the voltages drop by .2v each. Could this be why it still does not work? Are iphones just that picky about the voltages on those two pins? I can plug an android phone in and it charges just fine.

 

[(*steve*)]

Yes iPhones are picky. Can you point us to the reference you found and mention again the exact model of iPhone you have.

 

[bigone5500]

I found this instructable and thought I would give it a try.
http://www.instructables.com/id/Modify-a-cheap-USB-charger-to-feed-an-iPod-iPhone/
I have an iphone4.

 

[(*steve*)]

This is a little more authoritative and gives you some background. Note how things keep changing.