Might not be a bad battery. I would get that battery picture, but I had an application which reported the voltage directly, and it always gave reasonable numbers. The app was called something like GPS Data. Later, my phone failed. Don't know if that's related or not but the old battery works just fine in the new phone!
You could try measuring the voltage with a voltmeter, but I don't know if you can do that without opening the case. Maybe some of those little tiny holes go to battery voltage? Or maybe can see it with a micro USB plug or whatever that is?
Of course, maybe it's your charger?
Caveat: I'm not much of a phone or computer guy. Be skeptical.