Curious: Common positive solar on a common negative van?

[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]

I mean the panels much be grounding to the body of the van, no?

No, most panels are floating and its up to the installer to decide where the cells are relative to ground (series panel strings... ).

[paulca]

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

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.