Background: A while ago I noticed that my iPhone was crashing a lot. And I don't mean freezing, I mean the screen would go black, with a "CRC ERR!" kernel panic in the log next time I'd boot it up. After several days, I deduced that this was being caused by the battery emptying without the phone registering it as being empty. The error was caused by the battery genuinely running empty, so that instead of going into its semi standby mode when the battery is almost empty, the phone would simply turn off instantly at the moment of no battery power left. This explained not only the panics, but also the fact that until charged, the phone would get as far as the Apple logo before crashing again. What I have is a battery which is not reporting its status correctly to the OS, resulting in a false battery readout and consequent crashes when it runs out of juice while the system *thinks* it still has plenty left. This problem is strangely intermittent. For example, last night the battery went down to around 2% normally and then automatically shut down, the way it's meant to. Charged up normally as well. However, today, the battery has been stuck at 85% for several hours, meaning I am now charging it because I don't know how much it actually has left - it could well be almost empty given how much I've been using it. Turning the phone off and on again will fix the battery indicator, but carries the risk of sending the phone into a state in which it will randomly have these CRC crashes consistently until the next time it's charged - empty or not. This whole situation is incredibly irritating as you can imagine. Can anyone tell me specifically what mechanism is likely behind this? I'm posting here rather than Apple Discussions because I'm sick to death of "take it to a store" every time someone asks a technical question. I'm interested in devices and I'd like to know for myself what the issue is here instead of the stock "get it replaced" which seems to pervade a lot of Apple communities - for instance, if it's likely to be the battery itself that's broken, I can replace that myself for about €7 instead of sending it to a repair place for €50 and not getting it back for a week. I'm in Ireland so there are no actual Apple stores or genius bars, only authorized service places - as I say, not knocking on Apple but I really detest this "give it to an expert and let them handle it" ideology which seems to accompany Apple forums, I want to know how things work and do it DIY if I can Can anyone shed any light on what's going on here? NOTE: It's an iPhone 4S with iOS 6.1.3, haven't upgraded due to the god-awful layout my unfortunate father has been stuck with since he upgraded his! Been using this iOS since the day it came out with no problems though so I doubt that's contributing to whatever issue I have.