Have you ever noticed that one moment your iPhone or iPad is reading a certain battery percentage, then all of a sudden it drops 5 or 10%? Have you noticed that it sits at 1-2% for a very long time? Have you noticed that as soon as you plug it in that it suddenly jumps up by tens of percent?
All of these symptoms give an indication that your device is no longer able to accurately predict the amount of juice that it has in its battery. This doesn't necessarily mean there is anything wrong from a hardware point if view, more that you need to teach it to present the correct level of power to you - this is called recalibrating the battery.
You can recalibrate your iPhone and iPad battery with a few simple steps:
- Use the device until it powers down of its own accord
- Leave the device off over night or for at least several hours
- Plug the device in and wait for it to start of its own accord
- As soon as it has started up and you are at the iOS home screen, power off your device
- Leave the device off whilst it charges to 100% and let it charge for a good few hours after it is full
- Unplug the device
- Power the device on and monitor how the battery percentage fairs, if it still isn't quite right, repeat these steps again. If several attempts fail to resolve the issue then a clean install of iOS (not a restore) would be an appropriate step before you have to admit that it is an actual hardware issue
Why does your battery get like this? I'm not sure, but I would assume that plugging the device in for partial charges doesn't help. It would be helpful to carry out these steps on a monthly or bi-monthly basis.