- Fully charged LiPo 3S battery voltage is 12.6V (nominal 11.1V)
- Fully charged LiPo 4S battery voltage is 16.8V (nominal 14.8V)
- Your NUC can be Powered from 12VDC - 19VDC Power Supply (nominal 19 VDC)
- So, from the above data the choose should be in favor for 4S (the 3S has to low voltage range).
I agree. I would also recommend that you use a DC-DC "buck" converter to ensure that a clean and consistent supply is made available to the NUC. Here is an example of what I am talking about: Mini-Box.com: DCDC-NUC, 6-48V automotive power supply for NUC, 12V or 19V output.