Ian G
Active member
The only requirement for an earth is that it can reciprocate the current draw of your most demanding accessories and you are both right - it must be "good" in terms of having a low resistance at those loads.
Wire all the way from the back to the engine bay should be "good" if you choose thick enough wire, less so on longer runs with thinner wire at which time it becomes an interior heater. But suitably specced, it's fine and also you can predict the conditions far better, you know for example that 4awg wire will offer about .25 ohm per foot and go from there, voltage drop from a charged battery over that distance will certainly be within tolerance.
However, the shell itself also can provide sufficient current, problem is it's more difficult to measure and less predictable, and often requires more ingenuity to get a good contact point. Hence why many people prefer running a wire. Personally I would have no problem with a local earth, in fact would prefer this option - it's more simple, less expensive and lighter. And done properly, just as effective.
Wire all the way from the back to the engine bay should be "good" if you choose thick enough wire, less so on longer runs with thinner wire at which time it becomes an interior heater. But suitably specced, it's fine and also you can predict the conditions far better, you know for example that 4awg wire will offer about .25 ohm per foot and go from there, voltage drop from a charged battery over that distance will certainly be within tolerance.
However, the shell itself also can provide sufficient current, problem is it's more difficult to measure and less predictable, and often requires more ingenuity to get a good contact point. Hence why many people prefer running a wire. Personally I would have no problem with a local earth, in fact would prefer this option - it's more simple, less expensive and lighter. And done properly, just as effective.
