Why does it take longer to charge with usb than a regular charger?

A. 1

This is because the charger has more current.

Gentleman 8 years ago 0

OK

A. 2

Chargers have a lot of current, so they can supply about 1A or 2A of current.
However, in the case of usb, it does not supply such a high current because it is originally for communication purposes, not for charging purposes.

Gentleman 8 years ago 0

OK

A. 3

USB was originally developed for the purpose of data transmission.
At the same time, it can operate while supplying light power.
It wasn't designed to be used for smartphone charging purposes that require as much charging as it is now.

You might think that it's okay to charge it up now,
Then, it is not possible to increase the amount of current because over current may flow through existing USB products.
We could develop a completely different standard of ports.

Gentleman 8 years ago 0

OK