Why dont generic USB chargers work?

apple uses a proprietary usb adapter that will only work with their cables. other cables will not match up with the pins in the iPod. i don't see what the big deal is with using the apple cable though? you are supposed to use the manufacturer cable with most mp3 players anyway; it's not a thing exclusive to the iPod.

apple uses a proprietary usb adapter that will only work with their cables. other cables will not match up with the pins in the iPod. i don't see what the big deal is with using the apple cable though? you are supposed to use the manufacturer cable with most mp3 players anyway; it's not a thing exclusive to the iPod.

The problem I'm having isn't with the cable; I'm fine with carrying the ipod cable. It's just that the ipod (and cable) will charge from my laptop USB port but not from a generic USB charger or even a powered USB hub (if it's not connected to a PC). Every other USB-powered device I have works with any USB charger as does every MP3 player I've owned in the past (except those than ran on AAs or AAAs). I don't have a shuffle or older ipod, but I was under the impression that those *do* work with generic USB chargers. Correct me if I'm mistaken.

Also, the pins on the ipod cable do match up with standard USB cables, at least externally. I don't see how it wouldn't if it can plug into a standard PC USB port.

I'll have to experiment later. I'm going to try plugging my nano into a PC without iTunes. If my nano refuses to charge up on an iTune-less PC, then there is some communication that the nano is looking for before it will accept a charge. If that's the case, my suspicion is that there is some sort of chip or IC in the Apple-brand charger that sends the same verification code as the driver software. In other words, a dumb (power-only) USB port won't work.

If I had an Apple-brand charger, I would test the two inner USB leads with a digital multimeter. Power for USB is supplied on the two outside pins (1,4), data on the two inside pins (2,3). A power-only port should either be missing the two inside pins or else (I'd imagine) not have them connected to anything. I should see infinite resistance across pins 2 and 3 on a dumb port. I suspect an Apple-brand USB charger will register some kind of activity on the two inside pins and/or a non-infinite resistance.

The other thing I may try is to put a piece of paper or tape over pins 2 and 3. That will allow power but no data. My brother does that with his Sansa so he can listen to it while charging (otherwise it goes into synch mode). If my ipod refuses to charge with those two pins covered, then there is definitely data that starts the charging. Shoot. I could have easily tested that theory in the time it took to write this. It's late. I'll test it tomorrow.

If the nano requires communication from the charger, then I'll just have to bite the bullet and buy an Apple charger or some other name-brand that guarantees compatibility. Or return the nano to Costco. But if it's just some funky wiring shenanigans, maybe I can rig a cable or an adapter or something.

I'd appreciate any definitive info on this. If there is a verification chip in the Apple charger, I'd love it if someone came up with a cable that contained the chip so I could just use any generic power-only USB port. I'm also hoping that there is a good consumer-friendly reason Apple chose to make the nano 3g not work with generic USB. I hope the reason is not just a desire to make everyone pay $30 for a charger with >50% profit margin. I thought the days of Jean Louis Gassee were done.

Sorry for the long, thinking-out-loud post.

Nope, doesn't work with the external batteries. Damn!!

G26K, thanks for you input! Curious, but your results are different than what I'm seeing. My Dell laptop USB charges my nano just fine but quickly shuts down when trying to run my external 2.5" hard drive. Laptop USB ports are notoriously stingy with power. In contrast, my Belkin USB 7-port powered hub with it's massive 2A power supply, much more than the 1/2 amp (500ma) you mention, fails to charge my nano unless connected to my laptop.

I also tried my Monster USB car charger, made and marketed for the 1st-gen Shuffle. It doesn't work either. I've been too busy to run any other tests, especially since I'm watching the Sox game right now. Hopefully tomorrow.

RJ, Let me know how you come out. I have seen the nano 3g over current the USB on my Clevo Laptop, but only rarely and not since I added the wall wart for the 7 port hub I am using. I re-checked the others I mentioned to ensure I had it straight ( I am getting to that age!) and they work as mentioned. Good luck...K

My experience is very similar to that of RajaJaja, except that I have not even tried a generic USB charger -- was going to make one, but that's now on hold.

Attach cable to nano but leave USB end of cable not connected to anything - nothing :) (duh)

Attach cable to nano and dumb USB power (no data) - display light comes on but no charging
I did this with a machine with no RAM, but +5.05 Volts coming from the USB port

Attach cable to nano and desktop "A" USB without iTunes installed - initially same as dumb power until Windows installs drivers and/or service - then charges and says "connected"
On this one when I ejected the drive it stopped charging (lightning bolt went away)

Attach cable to nano and desktop "B" [I]USB without iTunes installed - Windows already had drivers it needed, connected and charged and continued charging after drive was ejected. On this machine also booted up Puppy Linux and it connected and charged.

Attach cable to nano and different desktop "C" USB with iTunes - charges and says "connected"

I also noticed that on Desktop "A" from a cold start there was no charging until after Windows booted. On Desktop "B" from a cold start there was first charging, then it stopped partway thru the boot process, then began charging before Windows had booted and continued to charge.

Sure looks to me like the computer needs to exchange some minimal info with the nano to initiate charging. If it's using a similar charging controller chip as the mini, this wouldn't be hard to implement. Can't account for what G26k is seeing, though. Maybe he got an unlocked one! :)

Attach cable to nano but leave USB end of cable not connected to anything - nothing :) (duh)

Ok, I should have explained that note was to show that just plugging the cable in didn't turn on the display -- the cable had to have power in order for the display to come on. However, as the other tests show, having power is not sufficient to initiate charging.

Digging further, I discovered that there used to be no official spec for USB charging. An official spec was added in March of this year:
http://www.usb.org/developers/devclass_docs/batt_charging_1_0.zip

There are now detailed specs for dedicated chargers, in particular, any dedicated charger must short the D+ to the D- line. This is one way a device (like an ipod) can immediately tell if it is attached to a charger, a host, or a hub. Sure enough, the working Griffin charger has pins 2 and 3 shorted together while my older (pre-2007) USB chargers do not. Mystery solved?

In short, it looks like the only thing going on is that Apple is following the new USB spec and is looking for a shorted D+ and D- pin. Older, non-compliant chargers simply will not work. Pull up resistors appear to *NOT* be at issue. According to USB specs, pull up resistors on the D+ and/or D- line are there only to identify a device as high-speed or low-speed.

The final test would be to short pins 2 and 3 (D+ and D-) on my generic USB charger. I think I have a conductive pen somewhere. Alternately, I'll have to open up a charger and solder a wire to the leads inside. If a shorted charger works, then the mystery is definitely solved.

Far from doing something proprietary or anti-consumer, it looks like Apple is just following the new official battery charging USB spec. .

The boxwave adapter, then, probably just has the 2 pins connected. I could easily make the same thing with a quick solder job or conductive pen. However, it may just be time for me to get newer USB-compliant chargers for all my devices.

RJ, thanks for the USB charging spec. It explains a lot, and I think you have sussed out correctly what is going on with your chargers. It also explains why the unit won't charge from a USB port until the port is enabled or configured (according to the USB 2.0 spec, the data lines before then are in a high impedance state--basically open-collector, I guess).

Interestingly, it also appears to indicate that depending on what method Apple is using to detect the charging device, the nano could possibly charge from a dedicated charger and from a host or hub, but not from a "host charger" or "hub charger".

I agree that Apple is probably not doing anything nefarious here, just following the existing spec which is best practice and hopefully, part of their corporate standards to do so.

Thanks again for the info and discussion.

I'm not sure but I think Griffen Technology offers a charger that will work for apple and other Mp3 players

I have a generic charge and that is the only thing I have ever used to charge my 3g 8gig Nano since the day I bought it. A USB charger is a USB charger is a USB charger. They all use the same pins for voltage input. Cost me $9.99 at Walmart. Completely charges the Nano in a few hours. The Nano runs all week on one charge.

How much is your listening time per day ?

I bought a generic 2x usb charger from walmart for $15. it takes ANY USB input so you can use whatever wire you want so long as one end fits standard USB and the other fits the device. we got one before going to mexico because we wanted to charge our nano 3g without lugging the laptop or paying $30 each ($60) for 2 chargers with the apple icon. $15, we got one charger that charges 2 usb devices at once. Works flawlessly we used it for our cameras and our ipods. So much nicer than 4 adapters for travel.

RajaJaja,

Not sure if you have had a chance yet to execute your plan...
"The final test would be to short pins 2 and 3 (D+ and D-) on my generic USB charger. I think I have a conductive pen somewhere. Alternately, I'll have to open up a charger and solder a wire to the leads inside. If a shorted charger works, then the mystery is definitely solved."

I bought an older - very cheap USB charger - that would incidentally charge an iPod Mini and a 4GB iPod Nano 3G (Silver). I have an 8GB iPod Nano 3G (Red) which would not charge off this charger. The lights come on - but no lightning-bolt.

So, I took the charger apart - and soldered 2 x 100 ohm resistors between the D+ and D- pins. Checked the impedence on my multi-meter and it read close to 200 ohms - as stated in the new USB spec.

No luck, however. I even went so far as to trying a single 100 ohm and then direct connecting the 2 pins (as the USB charging spec indicates that 200 ohms is the MAX)

Just wondering if you had any luck either?

i have built a wall charger for the iPod Nano 3G, which converts 9V to 5V (usb standard) using a 7805 voltage regulator,and soldered the D+ and D- pins together. It does not charge the ipod, but did work on one of my friend's sony mp3 players. Funny thing is : the display lights up when i plug in the usb , but no lightning bolt .. darn..

Now, the 7805 can handle 1A current. That's double than the specification of usb 2.0 .Also,the data pins being soldered together, as required by the usb charging capability, yelded no results.

Rajajaja, sorry to burst your bubble :(