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I've got several devices with a mini-B USB receptacle - including my mobile phone/PDA and some headsets. Each came with its own AC adapter. I'm wondering if I can charge any of these devices from any charger with a mini-B USB plug - (1) AC adapter (2) car charger (3) computer USB port with A-to-mini-B cable.

With wall warts I know you've got to match voltage, polarity, DC plug, and the charger must supply enough amps to power the device. But if the charger has a mini-B USB plug, does that take car of the voltage (+5V) and polarity?

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Yes it does, in terms of polarity and voltage, but not current. Some chargers short pin 5 (iirc) in order to tell the device that "hey we're breaking the USB standard here and you can draw more current."

Motorola phones will happily send 750 mA down the line, Blackberries 800 mA (that may be reversed). Usually extra current is just extra capacity and you're fine--it won't hurt a device. Under-current, however, will most likely fail to charge. Poorly designed devices may malfunction.

The USB 2.0 standard is for a device to draw 100 mA--and then ask for more current; most devices don't follow that part of the standard. (I have a device that does...and it has a mode that says "draw 500mA no matter what")

USB 3.0 will increase the currents allowed to 900 mA, and allow 150mA inital draw.

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  • In addition: you can short the data pins (2 & 3) to indicate you're a charger and then the device can draw 500mA without issue.
    – Broam
    Jun 14, 2011 at 20:16
  • The USB-BC 1.0 spec came out in 2007 to define how devices that needed more than 500mA to charge should act. In 2009 this was updated to USB-BC 1.1, and to 1.2 in 2010. These updates increased allowed current to 1.5A and then 5A. There were many devices made then and still devices made now that do not comply with USB 2.0 and USB-BC on voltage and/or current. The claim that by using mini-USB the voltage will always be the same is not true, that was a problem then and continues to be a problem still. Because of better enforcement of the spec the problem has lessened but it is not gone.
    – MacGuffin
    Jun 28, 2021 at 7:47
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I have had a problem with our GPS. It and my blackberry have a mini-usb connection, yet the GPS does not work on that charger. I would have said no for sure before I saw this with my own eyes, as I would think the very nature of USB would require the same size to work the same way.

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Check the Voltage/amperage:

  • If they match then there shouldn't be any reason why it wouldn't.
  • If they don't match, I wouldn't bet my equipment on it.
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  • I realize this is an old question and my comment is in that context. There were many devices that used the mini-USB connector with non-standard voltage and current so care should be taken when mixing and matching power supplies. Early micro-USB devices had this problem too. At some point some big name companies like Apple, Google, Amazon cracked down on people that violated the USB charging spec and put an end to most of the problem. As I write this there does not appear to be near the problem as there once was but care should still be taken when mixing up USB chargers.
    – MacGuffin
    Jun 28, 2021 at 6:55
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I think if it's the mini USB plug it's a standard connector and can be used on any device.

So far my HTC Hero hasn't had any trouble with the wires I got for other devices.

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