@thor
I have a charger of an older Nokia model, and it says it outputs 3.7v at 355mA. But I also know those phones have a standard lithium-ion battery. And you need about 4.2v to fully charge those. So not entirely sure I trust the label. In fact, I don't trust it so much, that I tested the charger with a multimeter, and it says it outputs about 8.4-8.5v, which is double of what I expected.
I'm guessing there's some trickery involved and when the charger and the phone actually shake hands, that voltage gets halved to what it actually needs.