How do I keep CPU off when charging?
Long press on the power off switch while plugged in, next tap on the power off prompt.   When it powers off make sure the charging light remains on.    If light is not on press power on quickly just so that the battery percentage shows in the center, it should blank screen again and the charging light come on and remain on.  You can retest battery charge percent again anytime.  When ready to use  long press on power on/off to on and watch or wait for rebooting to take place.