Mustek Power Must 400 LCD User Manual page 8

3).When in battery mode, it will display as below. And the mark
will flicker every 1second.
Note: If I/P-V<40V input voltage will display "000"
4).When in off charging mode, it will display as below.
Note: the output voltage always is displayed as "000" in off charging
mode.
5).When in fault mode, it will display as below. "FAULT" character and
the reason of fault only.
Note: the fault code will be showed in fault mode.