Lightening bolt doesn't change to a two-pronged plug. How can I tell If my iPod Touch 5th gen is fully charged with iOS 7?
Other users have reported the same. you can just look at the indicate and guess. You can also turn on the Voice Over Accessibility feature and then tap the battery icon and it will speak the charge.
iPad: Configuring accessibility features (including VoiceOver and Zoom)
You can also get a third-party app.
Retrieving data ...