Rapid battery drain Galaxy A5

A friend of mine has the A5. And has had problems of rapid battery drain. Litterally 1% every minute or two. So I advised to wipe it and start from scratch incase there was something glitching?

Same thing happened again, so he sent it off to EE and they said there was water damage. And it needs a new charging port? He seems to think it's been no where near water, so I asked if it's been left anywhere with high humidity, or been on holiday recently, which he said no.

So I thought I'll change the port for him, which I thought was strange, but done it anyway. (Yes I managed to get the screen off in one piece)

Still the same thing.

What I have noticed, is the top back of the phone gets quite warm?

I was thinking a new battery, but with this part getting warm, I want to hold off and see what you guys could have in mind?

Many thanks.