Changed battery and charging port but still wont charge?

Hi there

I bought an iPhone (Just been factory reset) a few days ago and it seemed to be working absolutely fine once it ran out of battery I tried to charge it. Came up with flashing battery and plug with lighting on the screen when I tried powering up.

I do phone screen repairs so I changed the battery and the charging port however it still wont charge. I have tried different cable etc so it's not that. I have tried connecting to itunes and it says device is not supported.

I have seen that there is a small IC chip on the iphone 5 which controls the amount of charge and it the past these have been faulty. Although I have never seen one about a 5S.

Is there anything else I can do/Check?

Thanks

Matt