The USB standard only allows 7.5W (5V @ 1.5A) of power. By negotiating over the data lines, the supplier and consumer can agree to higher amperage and voltage (up to 100W in USB3, 240W in USB3.1) - but you need data lines for this feature.
Some USB condoms include a chip to do this negotiation (with the other device) for you - but you still have to trust the chip.
You may very well have experienced this with a very basic USB cable (with just the power lines) - people call them cheap or bad quality, but because of the lack of data lines - only 7.5W can be delivered.
Some USB condoms include a chip to do this negotiation (with the other device) for you - but you still have to trust the chip.
You may very well have experienced this with a very basic USB cable (with just the power lines) - people call them cheap or bad quality, but because of the lack of data lines - only 7.5W can be delivered.
https://en.wikipedia.org/wiki/USB