Picture of Modify a generic USB car charger to charge a 3rd gen iPod Nano
I have a 3rd generation iPod Nano. It detects it's connected to but refuses to charge from a generic car->USB charge adapter, but I didn't fancy buying an adapter cable or yet another charger specifically for the iPod, so I modified one I already had.

There's a chance that this could work for other USB devices (maybe an iPhone too, but I don't have one), but there's also a chance that this could fry your device, car, or perhaps eat all of the cheese in the house. If you're not confident, or not competent, you probably don't want to try this. I accept no responsibility for any bad things happening.

If you're vaguely interested in stuff like this, you should probably check out ladyada's MintyBoost! kit, which helped prod me towards actually doing this.

Step 1: Bits needed

Picture of Bits needed
You shouldn't need more than the fairly standard soldering tools, a multimeter, and a couple of resistors (not shown) -- I grabbed a couple of SMT resistors from an old CDROM drive.

If you want the very simple steps without any instructions, all I did was connect a 27k Ohm resistor from V+ (Pin 1) to D- (Pin 2), then another 12k Ohm between D- and D+ (Pin 3). Dead easy.

Leinho6 years ago
I am trying to do this with my iPhone 3G ... Cause the car charger does not charge.. I was about to do this with an usb extension.. rather than doing it right in the usb adapter.. I dont know which ammount of Ohms i need in every REsistor,.. i thought 100 ohms is fine.. Please tell me.. Regards
Stupid IPhone 3G, these are very picky about the charger used
davis65536 (author)  Leinho5 years ago
I think you probably want higher value resistors -- something in the 10s of thousands of Ohms range
chooper14 years ago
Can you tell me what the voltage measurements should be for the two data pins to ground? Cuz when I measure D- to GND and D+ to GND, i'm getting close to the full voltage that I get from V+ to GND, which doesn't seem right... but maybe it is.
davis65536 (author)  chooper14 years ago
Yeah, that sounds about right; you won't get a huge voltage drop across those resistors, but from your message it sounds like you've achieved success anyway!
h00ch5 years ago
Does anyone know if this will charge a PS3 controller?  "Normal" USB chargers do not work.
i think you should try it. because the ps3 is unknown what are the pullup resistors it needs to use.
danielemur5 years ago
does this work with ipod touch?
davis65536 (author)  danielemur5 years ago
Very probably.

I'd really be surprised if it didn't; it works for the iPhones and for every other iPod I've found.
mopk475 years ago
with 3 resistors added between 4 pins, works well according to simulation and actually test. the value of resistors would be: 5V-39k-12k-33k-GND. This config with produce a nice 2.7V and 2.0V.
acaz936 years ago
it works for the iPhone , too !
endolith6 years ago
iPods don't follow the USB-IF charging spec. They use voltages on D+ (2.0 V) and D- (2.7 V) to tell the iPod how much current it's allowed to draw. You can just measure the pins on a Griffin charger or whatever to test this.

Cell phones don't follow the USB-IF charging spec, either. I'm not sure if anything does. :)
khem23566 years ago
what is the resistor valua? in ohms
davis65536 (author)  khem23566 years ago
Errr... From step 1 of the instructable: If you want the very simple steps without any instructions, all I did was connect a 27k Ohm resistor from V+ (Pin 1) to D- (Pin 2), then another 12k Ohm between D- and D+ (Pin 3). Dead easy.
is this how it connects?
davis65536 (author)  khem23566 years ago
Well, assuming pin 1 on your diagram is V+ as it appears to be, then yes, that appears to be correct.
i did mod my usb charger, and it did work on my ipod vedeo classic. lol! thanks a lot!!!!
davis65536 (author)  khem23566 years ago
No problem. Glad it works.
gamer7 years ago
Thanks a lot!! Works for Sansa E2xx series! :D
davis65536 (author)  gamer7 years ago
Good news! Glad it works for you!
redlegoman7 years ago
This works for the ipod classic too. It's the resistors to the usb data lines which are important here.
davis65536 (author)  redlegoman7 years ago
Ah cool, thanks for the info.