I hadn't noticed this till recently when I made a few journeys in the car. While I thought it was charging the whole journey whilst using the sat nav, I was confused when I unplugged it at my destination to see it was 50% drained. When I looked in to it further, I noticed that when I plugged the cable in, to start with the battery charging indication symbol that appears top right would be the usual battery with lighting bolt. However shortly after it would change to battery icon with what looks like a plug. Anyway, instead of using the USB in car charger thinking maybe it wasn't powerful enough, I switched to an inverter and used the iPhone AC adapter and lead. This seemed to work. Anyway, tonight I just noticed that the same icon is now appearing whilst plugged in to the AC mains at home. You can see it in the image attached. Why is this icon different to the usual battery with lighting bolt!? Thanks. EDIT: Ok since learned the symbol means its fully charged, however that doesn't explain why it kept appearing in the car, when seemingly it wasn't fully charged, as reaching my destination it was at 50%.