Is it better to ground to the chassis or the battery? I know everybody says to ground to the chassis, but I think that's because the battery is under the hood and we don't want to run a +12V and a ground cable all the way from the amp in the back to the battery up front. I have seen it mentioned though (grounding to the battery), but I can't find where right now. Anyways, my dilemma is that I have a BMW and the battery is in the trunk anyway, so it's just as easy for me to do either... so which is better or does it matter?
It is best to have a ground wire about 18" long or so. It is always better to ground to the chassis. Corrosion builds up easier on the ground terminal on the battery. If you ground it to the chassis, you are less likely to have this problem. Where does the ground wire from the ground post on the battery go?... To the chassis