Why won't the battery charge an Iphone?

I have an Iphone 4 and I'm trying to make a portable solar charger. I just got a 4.8 volt 1800mah rechargeable battery. When I connected the usb to an old Ipod I have the battery was able to charge to Ipod. But, when I connected to to my Iphone nothing happens. All I did was connect the battery to a usb female which connected to the ipod. Why won't it charge my iphone?

Have a look at the iPhone pinout here:
http://pinouts.ru/CellularPhones-A-N/iPhone_connector_pinout.shtml

It looks as if there needs to be specific data connections for charging to begin. I suspect you need an original iPhone USB connector