I am using the provided Micro USB cable to charge the RFD8500. After a full charge (almost overnight) the Power LED lights solid green.
I follow the instructions in the User Guide (rfd8500-ug-en.pdf, page 27) for turning the device on or off. When I hold the Power button for 3 seconds the Power LED is turned off, I get a sound from the device and then the LED is turned back on solid green. The device remains like that until the battery dies after a few days.