It has an internal lithium-ion battery that's fully charged. It has a multicolor LED that indicates when it's becoming discharged by flashing and turns red when the battery is depleted.
I've undone everything that I've done so far during this adventure, including un-pairing the keyboard and starting over from the beginning. The keyboard battery is supposedly good for 60+ hours on a charge, and it has a standby mode that engages after 10 minutes of non-use. One exits standby mode by pressing any key and waiting 3 seconds. I've never seen the LED flashing, so I'm not sure it's ever been run down.
Online research into troubleshooting this model keyboard has me wondering whether the original pairing occurred normally, which is why I've redone that from the beginning. All's working well at the moment, but it will take a couple days of correct operation before I'm ready to believe that it's really fixed.
