1. NEVER allow the battery to get that low - charge it when it's between 50% and 40%.
2. It sounds like a dendrite in the battery. It gets to the point at which the dendrite forms (it's a chemical thing with lithium batteries that no one's figured a way around yet), then it should burn the dendrite out (because it's a short across the battery) and go back to the charge it had before, or just under it. It seems that your battery formed a dendrite that won't burn off. Precharging it may fix that - but the battery has to be replaced anyway, because it's just going to keep getting worse. (And phones don't precharge - you need an external charger for that.)
The problem is so bad that most manufacturers don't even cover it when the phone is new. (But the alternative - a lead-acid battery - would make the phone much too heavy to lug around.)
10-30-2016 04:13 PM