The Apple 8's original charging cable supports fast charging, but the maximum output is 18 watts instead of 20 watts. Apple has introduced a technology called \"Fast charging\" that can fully charge a device in a short amount of time while reducing charging time. The Apple 8's original charging cable supports this technology, but its maximum output is 18 watts instead of 20 watts. Therefore, the Apple 8's original charging cable can achieve fast charging, but the maximum output power is 18 watts.
This is not possible, because the maximum charging capacity of the iPhone8 is only 18 watts.