I run my Hani Mandl on a Heltec board via USB power supply. Sometimes I use a power bank as power source. That's why I thought about a litte soft- and hardware addition:
use one of the A/D pins with an appropriate voltage divisor to measure the "5V" voltage
test for the voltage every 60 seconds and
warn, if the voltage droppes below 4.5 V
close the servo and stop operation with appropriate screen message
This would prevent running low on battery while the servo is open.
I run my Hani Mandl on a Heltec board via USB power supply. Sometimes I use a power bank as power source. That's why I thought about a litte soft- and hardware addition: