If the Apple Lightning data cable is not working well. Generally, the fifth contact from right to left on the data cable interface is black. Because PIN5 is a power PIN, the material of the contact is copper (gold color). The copper will slowly oxidize under normal temperature + humidity and turn into green copper rust, but if it is under high voltage and high current conditions, it will become black copper oxide. During our daily use, when the electric contact port is exposed to sweat or dust and impurities in the mobile phone socket, a large surge during charging will cause the contacts to become black.
At this time, don’t throw away the data cable in a hurry. Take a knife or alcohol cotton to clean the blackened area, and it will be ok.
Tech leakers 
Jason