If power source can handle the NUC's power brick consumption, and has the proper capabilities regarding power, that shouldn't be a problem, this hasn't been tested as far as I know and could fail.
I cannot assure you it is going to work properly.
Power brick specs:
Input: 100-240V~1.5A 50-60Hz
Output: 19V 3.43A 65W max
If you require any further information or support, feel free to contact us back.
I heard people used NUC + portable powerbank to make a mobile robot. So I believe it should be possible. but the powerbank might be not too cheap.
That could also be possible, as long as the power source is enough to handle the NUC's power requirements.