Modify a Generic USB Car Charger to Charge a 3rd Gen IPod Nano




Introduction: 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

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.

Step 2: Open the Charger

You need to disassemble the charger (actually you could probably do this in a USB extension cable, but I didn't want any more clutter).

Take the fuse and cap out. Then you need to split the charger open. Mine was welded together so I had to saw through both sides of the case and then lever it open. Don't cut too deep with the saw or you'll end up going through the components of the charging circuit.

Step 3: Add the Resistors

You need to add two resistors. You should do a continuity test first to determine if your two central pins are connected to any others. If they are, you've likely got a different charger and this probably won't work.

According to the USB charging and power spec I should be able to simply short the two central pins (the data lines) and the device will detect that it's connected to a charging device and start charging.

I tried this first of all, but it didn't work (the iPod detected it had been plugged in to something, but refused to charge). I knew the iPod charged from my MintyBoost!, and after a quick look at the schematic and some playing with the multimeter, I decided it would be worthwhile adding a couple of pull-up resistors.

I don't think the values are that vital (the USB spec is quite forgiving), but I decided to try matching roughly what the MintyBoost! was giving, apart from the V+ to D- resistor, which was guesswork.

Don't forget to check that you've got the correct resistance between the pins, and that they're not connected to anything they shouldn't be!

Step 4: Test (and Rejoice)!

After reassembly I tested the charger with a device I didn't care about -- in this case a broken DG-100 GPS datalogger -- to check nothing (useful) exploded.

Next I tried all three iPods I could get my hands on. Success!

I wrapped the charger with duct tape to complete that "finished" look.



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22 Discussions

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

2 replies

Stupid IPhone 3G, these are very picky about the charger used

I think you probably want higher value resistors -- something in the 10s of thousands of Ohms range

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.

1 reply

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!

Does anyone know if this will charge a PS3 controller?  "Normal" USB chargers do not work.

1 reply

i think you should try it. because the ps3 is unknown what are the pullup resistors it needs to use.

Very probably.

I'd really be surprised if it didn't; it works for the iPhones and for every other iPod I've found.

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.

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. :)

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.

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!!!!