Can I use a common negative in a simple solar system?

[anoccasionalyachtsman]

I'm putting together a system for a dayboat, and for various reasons it's distributed between two boxes a couple of Metres apart. It would be really simple to run the +&- from the panel into box 1, where the -ve can be used by loads there, then the two run on to box 2 that contains the controller, battery and another load. (Box 2 sends various switched +ves up to supply box 1's loads).

The initial design allowed for separate to and fros with a 5 core cable, but I've subsequently nicked one of the conductors for another load.

The instruction sheet that came with the cheap controller shows everything as having separated -ves.

This is a similar unit.

 

[VicS]

With no information about your controller, other than a picture of something similar, its difficult to offer any advice other that to wire it according to the instructions supplied.

Maybe you could open it up to see of all the negative terminals are interconnected.

 

[anoccasionalyachtsman]

With no information about your controller, other than a picture of something similar, its difficult to offer any advice other that to wire it according to the instructions supplied.

Maybe you could open it up to see of all the negative terminals are interconnected.

Doh. Why didn't I think of that?

Problem solved, thanks Vic.

 

[anoccasionalyachtsman]

Oops. Not solved. It's the positives that are common. Need to look at my sketch and see if I can make that work...

 

[cherod]

common thot is to use an MPPT controller , the cheap one is only £15

 

[PaulRainbow]

If i understand the suggestion, it won't work.

A sketch of the proposed connections would help though.

 

[anoccasionalyachtsman]

Hi Paul, no, it'll be fine. All I need to do is reverse the loads in box 1 and I'll be using common positive and switching the negatives. Vaguely unconventional, and nobody who open it up will understand it, but isn't that what previous owners are for?