lods and billboards lightmap problem

Hi everyone.
I have a problem with trees and objects that combine lods and billboards plus ligthmaps.
Everything has its mapping on its channel 1, but the billboard map of the billboards do what I do comes out dark and does not look good … it has fried me …
If someone knows how to solve it or knows of some magical tuto or I know, please share it.
Thanks in advance.