Take a look at the two screen segment captures from my iPad 2 space two minutes apart. Notice that the battery level was reported at 95% at 7:24am. However, two minutes late, the iPad 2 reported 98% battery level despite the fact that I had not plugged it in to any power source to recharge the battery. So, what happened?
Battery level reports are only slightly less mystical than cellular signal reports (the ones customers see, not the detailed field test mode information). And, it in a way, it is a bit more complex because batteries slowly lose the ability to attain a maximum charge over time.
I’ve noticed my iOS devices fail to report a 100% charge after being given, for example, overnight to be recharged. Or, it sometimes seems the battery level is a bit off after use during the day. I’ve found that a soft-reset usually results in the battery level report being bumped up a bit. In the case of doing this after an overnight charge, it is generally bumped up to 100%. I do not know whether or not this modified charge level report is accurate, But, if it makes you feel better to see 100% after an overnight charge, you might want to consider a soft reset. I’ve found soft resets fixes a number of iOS problems. Shades of Ctrl-Alt-Del for Microsoft Windows.