USB Charging from mains
 

Is it a safe assumption that any item that is normally charged from a computer USB port that also has a mains charger (with a USB socket) to connect the charger cable to ...... will also be safe to charge any other box/gizmo that is also normally charged from a PC USB. It would seem so as they all use the same PC output .... but thought I'd double check ....

Thanks.

I'd say generally yes, but you'd want to check what the output of the wall/mains charger is as compared to the device. If it's 5 watts or less it's likely safe for most things (iPods, iPhones, Bluetooth headsets, etc.) Older iPods use less but generally are OK with chargers that have more wattage. Keep in mind that if you use it for something like an iPad which requires 10 or 11 watts to charge that it will take longer to charge one of those devices with a power adapter that has less watts.

Yes, it's all 5 volts DC, per the USB spec.

The only difference is that different versions of the USB spec support different power levels out of that USB port. The standard limit in USB 2.0 is 500 mA, and 900 mA in USB 3.0. Some modern smartphones and devices (e.g., Kindle Fire) need closer to 1000 mA. The iPad needs 2000 mA, which is not in line with the USB spec, but Apple does what it wants.

The device you plug in will signal to the charger or PC USB controller how much power it wants. If you plug in a device (e.g., an iPad) to a charger that can't provide enough power, the device will either charge more slowly or give a warning that it can't charge from the connected power supply.

If you plug in a device that needs less power than the connected supply can provide, the device will charge normally and draw only the power it needs.

In short, feel free to mix and match USB power supplies and devices. You won't break anything. At worst, your device may not charge from the connected supply.

Many thanks.

The adapter for the iphone and ipad supplied with the UK stuff charges at different rates, as mentioned up thread. You can use the iPad charger for both devices and charge at "high" power, but if you use the iPhone charger for the iPad it does it only charges at "half" power.

When travelling I therefore only take the iPad charger.

iPhone/iPad will complain that they do not charge (sth like: charging device not supported; not charging) - but they do charge! It just takes forever. IIRC the official charger (and the MacBook) recognise the iDevice and switch to higher amps, a neat trick that prevents regular USB devices from being fried.

This isn't actually true - it is the device connected to the port that draws power, up to a certain number of amps. The ability to deliver more power does not cause a device to draw more power. In other words, other devices connected to the port would work perfectly well, and would only draw up to the typical 500mA from the port.

Right -- the USB power specifications are only to protect the power source, not the device. A device demanding 500mA from a port that can deliver 2000mA is fine. A device demanding 2000mA from a port that can only deliver 500mA is not.

Many thanks for the replies. To double check that I've not misled myself from the detail ....... no harm will happen ..... stuff will either charge or charge slowly but nothing will blow.

Correct -- it will either charge, charge slowly, or not charge at all. You won't break anything.

Now if only they could make it so foolproof for plugging stuff into power outlets in other countries. :)

They already do for the most part. Most devices these days run on multi-voltages so all you need is a plug adapter for the country you are in.