A:Answeryou can use 18 watt or higher will work and when the battery gets 100% charged and it will stop charging on it own because they did a lab testing to make sure it won't fail to stop charging so they do pass all of the test that will stop charging when reached to 100% and thats it
A:AnswerFrom Apple's Question/Answer web site:
"Unfortunately not. You must have an iPhone 8 or above to get the fast-charging feature."
https://www.apple.com/shop/questions/product/MU7T2LL/A/18w-usb-c-power-adapter
A:AnswerNo, you need around 65 to 85 Watts for a MacBook Pro, depending on which model. This works best on iPhones. In fact I would recommend even higher wattage chargers for iPads. 18 Watts is quite low for anything but the iPhones.