Save only Light Cache as a png

[Archaine]

I am trying to get a 4000 frame animation to render before the sun goes supernova. I noticed that the light cache image is actually good enough quality and takes 60 seconds to generate. How do I save out just the light cache image and move to the next frame. When I set the subdivs to 1 it renders in a few seconds after the cache stage, but it makes it look worse than the raw light cache.

Image on left is light cache only (saved after canceling render stage) image on right is final render

[Archaine]

Solved - Checking don't render final image still saves the image with just the light cache.