In article , Danny D.
wrote:


probably what it consumes, not what it outputs.

It can't be the input because 100-220VAC times the maximum stated
800mA input current is 80 Watts (give or take) input, which would
be about right assuming 50% efficiency.

true.

note that the charger itself doesn't say 40w
https://i.imgur.com/8bl7ypU.jpg

usb devices initially get 100ma and then request how much power they
really want. the charger responds with how much it can supply.

That is interesting. So, when I plugged in the iPad, it "asked" for
100mA, and then it asked for more, so the charger gave it more?

100ma is guaranteed without doing anything.

if a device needs more (many do), they need to request more power, and
must do so using less than 100ma.

standard usb ports should be able to provide 500ma. a bus-powered hub,
such as a keyboard, can't supply 500ma to downstream devices (it could
only supply 500-whatever it takes) so it will decline any request,
which is what causes the 'this device uses too much power' warnings.

recent usb ports can source more current because of usb hard drives
that need 500ma to spin up the drive as well as phones and tablets
that want more to charge faster.

But, then, why did the cord melt?

it's hard to say without looking at it.

one possibility is a defective cord but there could be other reasons.

if you have a continuity tester, try checking the cable for shorts.