Some iPhone users (especially those with devices that've been in use for a while) encounter a problem where the device crashes once the battery gets low. For example:
"After updating to iOS 7 my iPhone 5 has been doing something strange. When the battery gets low (usually around 20-30%), iOS will shut down completely, and when you try to power the phone back on it flashes on the screen telling you to plug the phone in to charge it (saying that the battery is almost completely dead). The phone refuses to power on until you plug it in, but once I plug the phone in and power it back on, the battery life shows the last percentage it was at before it crashed (20-30%). This has happened to me more than once, so I know it's not just some crazy fluke." https://discussions.apple.com/message/23587500#23587500
"I have a 3GS that is almost 2 years old now and had a hard life. It has now developed a tendency to crash when the battery gets below 25%. it will restart using the top button ok but as soon as you put any strain on the battery it crashes when at this low level. When the phone is charged it seems to work fine." http://forums.macrumors.com/showthread.php?t=1139488
"I have a weird problem with my iPhone 5. My phone switches off when the battery is low. I was at 23% charge and just browsing facebook when my battery died. The other day I was at 13% charge and it switched off. Last week 17%.. It refuses to switch back on until it was plugged into the wall. I have tried restoring the phone and set up as new but I still have the same problem. It just seems to switch off when the battery is low at different percentages." https://discussions.apple.com/message/22284705#22284705
It seems to happen on various model iPhones and versions of the OS; it's currently happening to me on a heavily used two year old 4S running iOS 6.1.1.
TidBITS suggests that:
"The common element in these crashes is low battery life, usually under 20 percent, although one crash occurred at almost 30 percent. When I give the iPhone power, it restarts immediately and shows the expected amount of battery life remaining. So it’s not that the battery is actually running out; instead, [iOS's] power management code is freaking out once the battery level falls to around 20 percent. I do see a number of LowBatteryLog files in Settings > General > About > Diagnostics & Usage > Diagnostic & Usage Data, though their contents don’t reveal a smoking gun. Letting the battery run down completely and then recharging entirely to recalibrate it made no difference."
(NB. TidBITS writes about this as it pertains to iOS 7 only.)
So, my question:
- Do we know, technically, what is causing these crashes beyond simply "the power management code is freaking out"?
- Are there any software hacks, fixes or usage habits (beyond usual battery saving/care techniques and "just get a new battery/don't let the battery get low!") that might help avoid these crashes?
(I'm interested in general answers, but in case it's of use here are the low battery logs from my two most recent crashes.)