Charging the iPhone by connecting it to a computer VIA the USB to Lightning adapter is awfully slowly. Just get a wall charger adapter (the USB connects to it and it directly to the wall. Two posible problems you can find even if using the wall charger are:
* The charging dock is dirty or lousy, or both things at the same time. The solution is cleaning it.
* The U2 IC Chip is faulty. It can degrade within five years of use. years. if you’re not familiar with the battery and U2 IC Chip replacement, just find a service that can work with both. The Chippy replacement will be quite expensive, so my advice is to do the work only from the iPhone 5s and over. Talking of the 5s, I bought one in Jan 2014, and it keeps working. No battery problems, and the Chippy is still sound