200 watt system recommendations for camper

[CascadeOffGrid]

Does it make a difference if i get Controller with negative or postive ground?

Some solar panels perform better when a positive grounded connection to avoid surface polarization which can reduce performance. A positively grounded charge controller will operate the PV panels at a negative voltage with respect to ground.

 

[Dzl]

If this is the case, do you have any insight why 'high side switching' seems to be the default for charge controllers? Are there advantages that justify the cost?

Not sure what you mean?

They are usually buck DC/DC converter so the only switching happening is internal.

So this is the question that started this discussion:

Does it make a difference if i get Controller with negative or positive ground?

So what I'm wondering is, if its true that 'positive ground' = low side switching, and this is cheaper to produce, why would this not be the norm for charge controllers?

 

[BiduleOhm]

Oh ok. Well it's simple: most systems use negative ground so most SCC will have a negative ground too as you can't really use a positive ground component on a negative ground system (well, in some cases you can but it opens a bunch of problems, it's a bad idea...) even if it would be a bit less expensive to manufacture.

 

[Bob142]

So this is the question that started this discussion:


So what I'm wondering is, if its true that 'positive ground' = low side switching, and this is cheaper to produce, why would this not be the norm for charge controllers?

Based on BiduleOhm's response in post 24, I went back to the original thread again and realize that the whole conversation there was started by someone asking about a positive ground PWM SCC, not an MPPT. The low-side switching discussion makes sense in the context of PWM because of how it operates, but I suppose not for MPPT.

So now I'm back to all of my original questions and confusion about positive ground SCCs.

Edit: BiduleOhm responded again while I was typing this post. I'm less confused but still want to know how and when PG SCCs can be used safely.

 

[CascadeOffGrid]

Positively grounded systems are common in the telecom industry where the battery positive is actually grounded. I believe this is the main application of these charge controllers. If you were building a system from scratch, you could certainly choose a positively grounded system design and use these charge controllers. There is no problem in operating a system in a negative state with respect to ground if the system is designed that way. I have worked on a few older Sunpower 600V commercial Grid-tie PV installations that were positively grounded as well.

You could even integrate a positively grounded system into a vehicle as long as you did not tie into the factory vehicle negatively grounded system. I would not recommend this though as it could certainly create confusion and safety concerns for someone working on the vehicle in the future.

 

[tictag]

Positively grounded systems are common in the telecom industry where the battery positive is actually grounded.

Interesting, I mean from a physics perspective, this is actually 'more correct' when considering the 'real' flow of current i.e. electron flow, rather than hole flow.

 

[BiduleOhm]

I'm less confused but still want to know how and when PG SCCs can be used safely.

Simple: on positive ground systems.

If you chose to do a positive ground system then please put a sticker on said system to warn about it being a positive ground system. It'll avoid a lot of headaches for the next guy (also, that guy might be future you...) as we usually assume systems to have negative ground as it is for 99 % of them these days.