[SOLVED]Need help interpreting the serial output of a sensor

The Pico also has a VBAT pin which provides somewhere in the region of
4.5v when from USB or battery voltage when powered from battery, so I would use that: https://www.espruino.com/Pico#pinout

I'll try this tonight !

There's even a self-resetting fuse in there so if you draw too much
power (>500mA sustained) from USB it'll just temporarily cut out
without breaking anything.

didn't know that, it's cool