Pro Mini VIN Problems / can I use LI-ON 4s pack ?

Using Arduino Project Guidance
8

Not wise to draw power from a single cell in a battery stack, if that's what you mean.

As said...
"Might be wise to power the ProMini and the Neopixels with a 5volt micro-power buck converter."
Leo..

P.S. could use a car USB charger for that.