Phone screen turns black, worked at ifix but not at home.

So.

A while ago, my phone was half charged, but when I went to pick it up from the dresser, it was black screen. I tried charging it in every way I could, both computer and in the wall. I changed plugs. I tried restarting. Nothing appeared on screen and the computer didn't recognize it being in.

I take it to an ifix stand and he takes it out, and when he puts a new battery on top of it, it turns on again. He says my battery and everything works fine, he doesn't explain to me why it did that. The phone even still has the half charge it did when it went out. I have the battery changed, and go home.

It runs out of energy on the ride home, so I buy a new plug on the way and try charging it, and it's doing the same thing! Won't charge and computer won't recognize it, just a black screen.