Is it possible to charge a smartphone from a non-native power supply?

Question

Batteries

I recently bought a laptop and it came with a fairly powerful and weighty power supply. Now I want to charge from all available devices: smartphone, wireless headphones and laptop. Is it possible to do this, because the minimum specified output power is 15W (5V 3A)?

Here is a photo of the BP

Answer 1

Not the minimum, but the maximum. This means that when you try to connect something that consumes more than 3A to the power supply, it will either go into protection or, after a while, fail, possibly with special effects.
A laptop power supply usually outputs 18V, so it will not work to charge anything other than a laptop directly from it, a device designed for 5V will simply fail. The laptop itself will also not be charged from 5V, it is not designed for such a low voltage.