charging, no logo, and barely feel warm at lightning port

M8 i have an iPhone 5S that I found at online marketplace just for Rp 75.000. the owner said that the mainboard is okay but the screen is broken. So i want to charge and test the ring switch so I will say it's working when it vibrating.

But the reality, no, and the mainboard doesn't feel warm. I think the owner never turn the iPhone on for a long time. So I charge again n wait around 30 min and still... No. Then, I pull the lighting cable from the iPhone but when I touch the lighting male port, it feels warm and not the mainboard.

I still figure what's wrong with that iPhone. is the charging board? or something?

send help...

Thanks