why is my phone not charging?

I started this phone  not charging infrequently at first after one and a half year after using BV8000Pro. Occasionally my phone would charge ok but sometimes it wouldn't just detect the charger at all. Sometimes it would charge too slowly like 5% in an hour or two. I bought new cable thinking that it would solve my problem but it didn't do any good. At times I would have to set the charger plug at an angle to charge my phone. Now recently It stopped charging at all and the phone is now totally dead. In its dead state when I connect charger it shows Charging icon but charges upto 1% only. Now I don't understand where does the issue lie: the charger, the battery or the Charger port. 

Please help!