it is only charging to 2%

I have used all types of different plugs and cables. I have another ipad mini 2 that charges fine. but i cant get my ipad mini 4 to charge past 2% then it only last about 20 sec once unplugged. i have tried multiple batteries too. my question is how do i diagnose if it is something like the tristar chip or if something else is wrong. i also have a spare mini 2 and was wondering if i could get any parts out of it. Thank you