Mixing common positive and common negative DC equipment.

[paulca]

I have two solar chargers.

One is common positive the other is common negative.

If I draw the schematic of these in parallel with the same battery and different panels, in my head, I can't see a problem.  I mean if either the positive or negative between the two should touch there could be a short, but... that's always the case anyway.

The common positive controller will "float" relative to the battery positive.  However that is the same positive that is connected to the common negative controller anyway.  So they share the same - and the same + potentials.

Solar panels do have metal frames, however I'm not exactly sure that makes a difference.  If it's galvanically connected to one or the other and it's the same on all panels, the only current that could flow would be the differential voltage between those particular panels floating potential and ... that's always going to be the case of independant strings anyway.

Where is the gotcha?  Assuming you don't do anything stupid like not verify the earth is always - on both and don't connect the + and - to Earth reference at the same time!

EDIT:  I tested the common positive controller.  It's completely isolated from it's case and earth on both + and -.

[Terry Bites]

Share your schematic?

[paulca]

What I have so far.  Tried to show the common-ing through the blocks.