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Curious: Common positive solar on a common negative van?

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paulca:
So I was watching this:

I have the same charge controller, though a smaller model and a different brand.  (Mine is EPEver).

The thing is, mine is "common positive".  Automotive electrics are common negative.

My thoughts where, how could you have wired this up to a van at all?  I mean the panels much be grounding to the body of the van, no?

And when they connect the "LOAD" - and + to the van 12V system, surely that then forces the charge controller to float at -12V?

Surely this is unwise and could potentially (bad pun) been what cause the unit to combust.


thm_w:
Are you saying the case of your MPPT controller is electrically connected to +12V?

Solar panel cells are completely isolated from the aluminum frame. Usually you would ground the frame for lightning/safety reasons.

Someone:

--- Quote from: paulca on August 17, 2022, 07:57:22 am ---I mean the panels much be grounding to the body of the van, no?
--- End quote ---
No, most panels are floating and its up to the installer to decide where the cells are relative to ground (series panel strings... ).

paulca:

--- Quote from: thm_w on August 17, 2022, 09:07:36 pm ---Are you saying the case of your MPPT controller is electrically connected to +12V?

--- End quote ---

That's a good point.  I don't know.  It says it's common positive and I believe the 3 DC terminals (panel, battery and load) all have a common bus for +.

I never tested if the case was connected to either. 

thm_w:
If the case is isolated, and you run proper wires to each component instead of using a chassis as return, I'm not seeing what the issue would be.

Even if its not isolated, it could go into a large plastic enclosure.

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