I used 2 li-ion rechargeable batteries in series, an LM7805, some resistors, a capacitor, a switch and a green led to build this simple emergency charger. This charger will power any USB device including Iphones and Ipods with a maximum current demand of 1A. Apple devices (Iphone/Ipod) will charge properly without maxing out the 1A limit. The next stage is to build a “step up” converter to recharge the batteries via usb.
Majority of the components, except for the batteries can be found in ATX pc power supply :).
All the electronics and the batteries fit nicely in a tin can (I have to optimize the space to close it properly, I didn’t think of that during the built)
As you can see the emergency charger is “on” and the phone is charging (little red light on the top left and thunder symbol on the battery level of the phone)
Here you can see the rocker switch to power on or off the charger.