Thanks for the feedback. Of course you are right. My theory is that Android is doing something in the background even with the WiFi switch in the OFF position and the LCD screen locked. And these background processes unnecessarily consume energy. I had my device in exactly that state (WiFi OFF, LCD locked). If the eDGe would only be driving an ePaper screen then a fully charged battery should last for days. But it does not. It lasts for less than one day. So therefore I am interested to know whether one could stop Android completely and use only the eBook screen.