Avanti and jmole I admit that I misspoke by referencing the differences in "conductivity" between steel and copper.
I will also concede to my lack of higher education that it appears that both of you clearly have, that's cool! I rely on my well fed curiosity and intuition based on extensive travels and life experiences including the purchase/operation/and maintenance of several million dollars of various types of equipment and vehicles over the years. I also frequently mention my reliance on my brilliant 41 year old adult son assisting me with my often complex project ideas. (Fatherly plug,
www.SensorPush.com)
So please accept my apologies for swerving off course in this discussion that I will continue to push for the dedicated second conductor for these high output auxiliary alternators. Please refer to something that Einstein apparently said....."
If you can't explain it simply, you don't understand it well enough."
^^^ that's me! I get over my head pretty quickly at times, but I keep going. Haha
My concerns with this big alternator have always been based on seeing the many various problems that Roadtrek owners were having with there early use (mid 2013) of their GU option or "Underhood Generator" or auxiliary alternator. Some of the problems were issues with the early MB N62 PTO drive, those were mostly solved over the years. They also had what seemed to be a higher incidence of wheel speed sensor and possibly other sensor issues. (Before you ask, I have no data, but it was a big deal.)
I figured for the relatively small cost of adding the additional 2/0 copper conductor, twist it and place it in a tinned copper shield grounded only at the alternator I would have one less thing to worry about.
To the point of actually being surprised by how few people choose to not use a second conductor, but to argue against the need for it.
Maybe you think that it's "just DC" and not a concern? But the amount of EMI created with 4000 watts (up to 8000 watts in my 48 volt system) flowing through a single conductor and then using the chassis to complete that circuit is worthy of concern on any modern vehicle with sensitive electronics from end to end. And the issues go beyond that, the potential for frequency fluctuations and the noise associated are to be expected. (Going beyond my full understanding here)
jmole, you had it correct in this post you made back in march.
jmole
Active member
Mar 18, 2021
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45Kevin said:
"Any grounds to the body become common, whether they are all stacked on the same bolt or are on separate bolts.
This is true in theory; in practice, high amperage loads will cause voltage differences at different bolts across the chassis due to the resistance of the chassis itself, spot welds holding different pieces of sheet metal together, etc.
If you have something like an inverter grounded near a sensitive component, inductive voltage spikes from things like A/C turning on and off can possibly disturb the component. Automotive components are usually designed to take this kind of abuse more than consumer electronics, but it can be problematic."
Another point that I will re-iterate is that while this topic is being called "Grounding" we are really talking about using the chassis as conductor for this large amount of current. And yes, it clearly has the "ampacity", but along with that flow comes the EMI and associated noise, but now you don't even know where it is actually flowing. And it might even change based on changing conditions, wet vs dry, salt who knows?. Electrons always choose the path of least resistance. Plus you do know that the single positive cable is live with large amounts of EMI and noise.
For a small price I addressed all of this.
Here is a pretty good article in support of my decision to do what "I thought best". (A little poke, but please understand that I just want to help, learn more myself and in the end be friends. I truly do enjoy not being the smartest man in the room!)
Grounding for EMC is very important. It is not the same as grounding for safety and it is not the same as current return.
learnemc.com