I accidentally discovered a good diagnostic test for swollen batteries: (1) Remove phone from case and place on a very flat, smooth, hard, clean surface. (Gran

I accidentally discovered a good diagnostic test for swollen batteries: (1) Remove phone from case and place on a very flat, smooth, hard, clean surface. (Granite countertop, glass coffee table, etc.) (2) Give the corner of the phone a sideways flick with your finger. (3) Does the phone spin around and around and around like a top? If so, it may have a swollen battery. This probably doesn't work for every model of phone, but on mine, I noticed the phone's newfound ability to spin much earlier than I could easily see visually that the back of the phone was bowed.