My phone is dead, charging light is the only thing responding

[Android Central Question]

Hi. I have a rather old phone that does some funny things once in a while. It's a Sony Xperia E5 lite, and it has always frozen sometimes, even when it was new.
However this time I can't do anything. It was not charging overnight due to a bad charger, so when I woke up this morning I made sure it charged. It showed me the first charging screen with the red battery, then turned to white Sony screeen and on to the green battery charging screen and said 0%. I guess that's a pretty normal chain of screens when charging a flat battery.
Now it's been charging all day, and nothing has happened. The charge light is supposed to go from red to yellow to green, but the only thing it does is light up in red when plugged into a charger. I can't get it to show any screen whatsoever, I can't reboot it using the power/volume up reboot or any other combination of buttons that I know of.
I've tried plugging it into my computer hoping to be able to recover anything from the internal drive, but it doesn't see it at all, although the phone charges.

I suppose the battery is dead? It's not removable, so I can't replace it myself. I want to hand it in as there's still warranty on it and I want them to do something about the many, many things that's wrong with this thing, so I don't think I should get anyone to open it up and change the battery.
Does anyone know anything I can do to get just a little more life out of it so I can get my files? Or even better, how to get it to turn on?

 

[B. Diddy]

Welcome to Android Central! It looks like that phone was released some time in 2016 -- are you sure it's still under warranty? Is it a 2-year warranty, or did you buy the phone new within the past year?

If the battery is dead, there's not much you can do. Try leaving it plugged into a wall outlet for 12 hours straight, undisturbed, then try powering on again by pressing and holding Power for 20 seconds.