Charging circuit for P40

Hi, I have a Allison V1710 that is not airworthy so have mounted it on a trailer for static running and would like to have it charging the batterys. What I have is the generator and one other component but I am sure ther are some others so If any one can help with the drawings for the charging circuit for a P40 or even a C47 it would be much appreciated. Thank you Laurie.