Fast charging and slow charging are not applicable.
The fast charging port is compatible with the slow charging port, but the slow charging port is not compatible with the fast charging port. So if it is slow charging, which charging port can be used, if it is fast charging, only fast charging port can be used.
To achieve fast charging, three conditions must be met: First, the charging head supports fast charging; Second, the charged device supports fast charging; The third charging cable supports fast charging; The fourth fast charging head, the charged device, and the charging cable support the same fast charging protocol.