My Portable Ipod Charger or Any Gadget

I'll assume a standard USB1 & 2 type connector. The reason I can answer your question for the step-by-step is I did this same thing about 6 years ago.

1. Buy or find a four AA battery holder (or a small 5 V AC to DC converter)

2. I'd use NiMH batteries to keep the voltage below 6 V USB ~ 4.8 - 5.2 V, NiMH batteries can be as high as 1.33V/cell X 4 = 5.32V

3. Find a USB port from some dead computer or whatever

4. Wire the + side of the battery to the pin # 1

5. Wire the - side to pin # 4

6. Tie pins # 2 and # 3 together, THIS IS IMPORTANT I'll explain later

7. Plug in your standard iPod charging cable.

OK, first if you use Alkaline batteries you'll get voltages above which small USB charging devices may not be able to handle the heat & the device may end up being damaged. Since NiMH are good rechargeable cells these should ;last a good long time charging something as small as an iPod. I do NOT know at what voltage an iPod won't charge even if the source can supply the needed current, but that shouldn't be too difficult to find out with an adjustable power supply taking the place of the batteries.

#6 - The reason that I tie these pins together is to indicate to the device being charged that the power source is a high current source. It turns out that most USB charged devices use these pins both as data pins and if they require high current then probably just one of the data pins as an indicator of hi current charging capability. Something has to be on that pin, some voltage. The reason I think that connecting these pins together works because the device will sends a signal on the pins to see if it is connected to a computer, this signal goes nowhere BUT it sets a voltage on the pins which the device then interprets as the high-current source voltage and happily charges at its high current rate.

I tried this about 6 years by modifying a USB extension cable in this way. Without connecting the two data pins together the device would not charge, connecting the two data pins, # 2 & 3, together on the device side (not the computer side, leave those two unconnected) "fooled" the device into being able to charge at full current. I could then plug this extension cable into my computer to charge my devices BUT NOT have them connect to the computer. For an iPod this allows it to charge and play at the same time. I made other power sources and was able to use them as well to charge my iPod or other mp3 players and have them play as well.

I later found a USB standard reference that said that one of the data pins had to have a voltage on it to indicate to the device under charge that it was connected to a high current charger. I don't remember which pin but connecting the two data pins together seems to work for everything I've tried to date.

PhilKE3FL

Reply 10 years ago on Introduction

I forgot to include:
To see the USB standard go to Wiki: https://en.wikipedia.org/wiki/USB
and Step #3 can be done by cutting a USB extension cord and using the port side, the one we plug our USB cables into.