u/EasyDelight

Hi! So i bought one of this keyboards no so long ago, and i'm running into a little issue.

Is there any way to see if the keyboard is actually fully charged? I can use the FN+DEL combo but's that's more just an estimate, and the LED when disconnected the manual says Green is +80%. But when the cable is connected the battery LED just turns red. Never any other color. I tried leaving it plugged in overnight and it was still red. So i went to work for about 12 hours and now I came back and it's still red. Is it an issue with my unit? Or is it just like that?