Rather strange...
okay though.
Power management is handled by the embedded controller, which runs
proprietary fimrware. It is possible that the problem may have originated
there.
Oddly enough it must have been an anomaly because I plugged it back in and
the problem hasn't come back since.
Probably a one in a million issue or less frequent.
My Libreboot X200 doesn't have this bug (20160818 released)
Don't ask here, ask on Libreboot mailing list/IRC.
It would seem that my x200 libreboot laptop when not plugged in beeps even
though it is at 80% battery life.
I know now it this bug has to do with low battery life, but this clearly
isn't the case.
Although oddly enough it has stopped but I don't know why...
Could be that anything under
