If you're going to rely upon only a frame ground, make sure you take a wire wheel on a drill to the area you are going to bolt the ground, and clean it down to bare steal. Many frames already have a lot of holes you can take advantage of, so no need to make a new hole, but DO make sure you clean the frame coating off.
I would not run a ground wire smaller than my positive wire between two batteries. If you've run 4 gauge wire for positive, and want to run a ground between, then that ground should be 4 gauge as well, nothing smaller... ever. Your ground from the aux battery should be 4 gauge or larger. With this solid ground point, it is unnecessary to run other ground wires in between.
Some people think it is necessary to run your ground from the rear battery to the front battery and avoid the frame ground. This is to avoid ground loop issues. I tend to think this way, but I have installed them both ways.
Anyway, i ordered the "cheap" solenoid off amazon. In the diagram, he uses the "good" solenoid. My question is, the cheap solenoid has two terminals on top and the good solenoid (used in the diagram) only has one. Should I run a 12gauge wire from each of the two top terminals on mine and splice them together prior to plugging it in to the fuse box? or do i only need to run it from one? thanks.
