Voltage

Get voltage status

sudo /opt/vc/bin/vcgencmd get_throttled

The bits on the returned number mean

Bit Hex	Value	Meaning
0	1	Under-voltage detected
1	2	Arm frequency capped
2	4	Currently throttled
3	8	Soft temperature limit active
16	10000	Under-voltage has occurred
17	20000	Arm frequency capping has occurred
18	40000	Throttling has occurred
19	80000	Soft temperature limit has occurred

A value of 0x50000 means 16 & 18 -- from the boot moment up to now Under-Voltage has ocurred at some point as well as Throrrling has occured.

Source: https://github.com/raspberrypi/documentation/blob/master/raspbian/applications/vcgencmd.md