No, it is not possible to force Photos to curate the photos Library while on battery power. But you can let the Mac connected to a power source over night, when you are not using it and let it run then. We can use Photos without problems, even if the curation has not finished. It is only necessary for a nicer layout of the Days, Months, Years.
How large is your library? For my main Photos Library with more than 50000 photos and videos it took several months to finish the curation. I did not mind, as I am rarely looking at the Days, Months, Years, as it is hard to recognize the photos in the tiled view, because they are cropped and only a curated subset is shown. I prefer to seem photos as I have cropped them in the correct aspect ratio in All Photos or my albums.