Quote:
Originally Posted by DoctorM
Years ago I had someone at Radio Shack (if you remember those) tell me the opposite. That an adapter's amperage was more important than voltage. For example a device that runs on 8 D-batteries, which should be 12V can run just fine on 10V if the amperage is high enough. Maybe lower voltage is fine since batteries lose voltage over time, but higher is dangerous?
What is troubling is that the adapter has a list something like this:
5V : 3A
7.5V : 2A
15V : 1A
From a wattage standpoint that makes sense since Power (Watts) = Voltage x Current.
But does that mean a reader drawing 1A is getting 15V? That seems like an issue.
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USB specs are 5V, 500mA.
More voltage might kill your device (allowed voltages are usually from 4.x to 5.x but better safe than sorry)
More current won't kill your device because it is your device the one that draws current.
If the adapter comes with a knob to change voltage then it is regulable by the user and will use the voltage you setup. If not and it is a "normal" mains to usb adapter you'll get 5v (up to 3A) unless the power circuit of the device you're going to charge negotiates for more voltage.
In all the cases the specs of your charger is: xV (up to yA) and the one that decides the amperage is your device, not your charger.
Sorry about my english
