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I have a converter for my cellphone that converts to 5V, 650mA. I guess the voltage (5V) is the same used in USB, but the amperage is 150mA higher. Is it unsafe to charge my iPod at the higher amperage?

Aurast
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    see here: http://electronics.stackexchange.com/questions/34745/choosing-power-supply-how-to-get-the-voltage-and-current-ratings/34746 – stanri Feb 21 '13 at 04:03

2 Answers2

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In Short, yes, you can charge your iPod touch with a charger that can deliver 650ma.

It is safe to use charger with higher amperage but make sure the voltage is 5V regulated.

Another point to note is that iPod will only charge if the USB D+ and D- signals are brought to a certain voltage level. Generic charger not made for iPod may not charge your device.

Chetan Bhargava
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As @ChetanBhargava pointed out, you should be able to charge your iPod without a problem. I'm not sure if the statement, "iPod will only charge if the USB D+ and D- signals are brought to a certain voltage level," is correct. It may be that the iPod tries to communicate with the charger and negotiate/figure out, how much amperage it can provide (like a standard USB host.) And if there is no data, ie. D+ and D- are floating/not present, it just assumes the charger can only supply 500mA. (I think 500mA is the minimum for USB, but once again, I didn't double check.) [See @Passerby's Comments]

Is it unsafe to charge my iPod at the higher amperage?

No. FYI, the charger can supply up to X amps, in your case, 650mA. It is the current draw of the iPod that could 'pull' too much current, causing the charger to overheat or fail. This wouldn't happen in your situation... I just used it as an example.

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Garrett Fogerlie
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  • I'm 100% sure that you have to bring up D+/D- to a certain level to charge an Apple device. If the apple doesn't charge, it is safe to eat the apple! – Chetan Bhargava Feb 21 '13 at 06:20
  • @ChetanBhargava is it that they just need to be tied to ground so they don't float? Or does one need to be at +X thus the other at -X? – Garrett Fogerlie Feb 21 '13 at 06:22
  • No! They can't be connected to ground to charge. I have tried them myself!. I would have made a lot of money at Apple if I designed that proprietary charger. I don't know the PD that they have to be at. One thing I'm sure of that is that they have to be at a certain PD to begin the device charge. – Chetan Bhargava Feb 21 '13 at 06:32
  • @ChetanBhargava Very interesting! I just brought that up in [chat..](http://chat.stackexchange.com/rooms/15/electrical-engineering) – Garrett Fogerlie Feb 21 '13 at 06:39
  • Cool! an iPod won't charge if D+ and D- are not at a certain PD WRT ground. – Chetan Bhargava Feb 21 '13 at 06:42
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    Apple uses a voltage divider (resistor pair) on each line to signal on the data pins. It uses it to determine what type of charger it is (Supported or unsupported) and how much current it can pull (low, normal, high). There is no public name or standard for this type of signaling, but many manufacturers have started using, while many still use floating/unconnected d+/d- usb charging. The PS3 Sixaxis is weird because it requires usb enumeration before charging. – Passerby Feb 21 '13 at 06:42
  • So, no, the ipod/ipad does not enumerate with a charger. And the Ipod will not work on a dumb usb charger without the resistor-divider. – Passerby Feb 21 '13 at 06:45