Hi, a newbie here So I got an old LG Optimus L7 from my cousin. It worked really great at the first two week but few days ago, black screen came up several times each day, and follow automatic shutdown. I told my friend using same model, then he lent me a mpj extended battery which he quarantee worked fine to see any difference. But unfortunately, the problem still appears. Now sometimes it can be turned on but soon shuts off after the logo comes out. Help please!