update: Well i got the thing wired up. Testing it on a car battery i have hanging around. Having the extra ground attached to the 12V- does not seem to do anything at all. It functions with or without it attached. Seems like a good unit so far, but have not hooked it up to speakers, only tested the video in. VGA does not seem to function, only RCA, don't know if this will be a problem for me, we will see.