How do i bake,or render, from one normal map into another?

Hi! the idea is to build and export a normal map of a brick wall texture…so i sculpted one brick and started duplicating it in front of a plane to bake the whole texture…but it gets very slow to work with sculpt duplicates…so i baked this one brick into a lowpoly mesh. it works, now i have all the lowpoly bricks with nice normal maps aligned…but how to go about baking this info into the final normal map since it is not a highpoly mesh anymore? i’ve searched the forum and tried using the normal map node in cycles…but it gets a weird result with the light info all wrong. any ideas guys? thanks in advance