Have you updated the firmware?
This is a known bug in a new firmware.
Connect the charger to the Reader while it is switched on then disconnect it. The battery indicator should display full charge after that.
Please remember, that even when you do not use the Reader it is still switched on. When you "Switch off" the reader you just clear the display and lock the keys.
Some of us are having problems with the battery indicator even though we have not upgraded the firmware. I read every day and I need to charge the reader every few weeks. So I am not concerned about the fact that one day my reader shows two bars (out of four) and the next day I have to charge it.