How to build a charger / power adapter for iPod

After several years of loyal service, the iPod nano, third generation of my son began to show signs of impatience: failed to light more even loading it with the USB adapter for PC (or Mac) except pressing reset for 10 long seconds  simultaneously   the middle button and the "Menu" botton.

 The problem was probably the rechargeable battery, now exhausted.

 For him thr next-generation iPod, but I wondered, why throw the old one?

I was reminded to build up a "doking station" to connect to the system for listening at home. Since the 220 V or 110 V network is always available, the battery problems should not give trouble.

 Actually, the connection of the iPod cable, terminating with a USB plug (fg.1), to a 5 V power supply was not without problems: Connecting the terminal 1 (red, 5 V) and 4 (black , GND) of the USB cable that will connect the iPod to a 5 V regulator (Fig. 2), the behavior of the iPod appeared somewhat unpredictable, unstable, and the battery gharging symbol was often no present on the iPod display.  

Analyzing the supply voltages for the (almost) original iPod, I noticed that the wires 2 (black) and 3 (green) were not floating, but related to potential, respectively, a little less than 5 V / 2 (green) and a little more than 5 V / 2 (white).

Having said that, I made a divider with 3 resistors 100K, 56K, 100K and I connected via points to white and green wires (see Figure 3). At this point, thanks to this iPod mysterious characteristic, all took to operate (and recharge) correctly.

NOTE: this operation is only recommended color who have a little 'familiarity with electronics. Not responsible for damage to the iPod!

Fig.1

Fig.2

Fig.3