Controller Location

[pappi49]

Just when I think that I amstarting to understand this all a little better I get to conflicting answers. That part does not surprise me but who they came from does.

Gizmo tells me to connect in series with a an MPPT controller while Ex-Calif tells me to connect parallel.

I was leaning to series as I understand this would allow me to run a little smaller wire for a greater distance. Fortunatly I have not yet purchased any of the components so I will just soak in more information and try to make an informed decision when I get ready to buy. I am leaning towards putting the system together myself as opposed ot a ready made system as that way I can customize my wire gage and length for whatever location I decide upon.

 

[Ex-Calif]

Both answers are correct.

MPPT controller can more effectively use higher voltages of series connections, especially when you get past 2 panels. Assuming 12V panels. 4 panels gets you up to 48 volts. That's where MPPT really starts to do some "good." Not that it won't be "some good" at 24V.

MPPT also can have better charge profiles.

However at 2 panels you can get away with a cheaper PWM controller so that's why we wired 2 panel systems in parallel. Call it the "budget" conscious solution.

Beyond 4 panels you pretty much have to have an MPPT controller. Also if you start with 2 and plan to go to 4 panels and beyond, you may want to start with an MPPT controller.

 

[Frank B]

Fortunatly I have not yet purchased any of the components so I will just soak in more information and try to make an informed decision when I get ready to buy. I am leaning towards putting the system together myself as opposed ot a ready made system as that way I can customize my wire gage and length for whatever location I decide upon.

It is good that you are gathering information BEFORE installing. That is what I did as well. Sadly, many come here saying "I already bought this and this, now how do I connect it." In many cases, the initial purchase could have been better.

Have you considered buying residential style solar panels? So-called RV panels are 18 volt 36 cell units, and work with PWM controllers. If you want to eventually add more solar, then please consider an MPPT controller to begin with. Yes, they are more money. But no one ever says that they have too much solar. Our 'needs' grow very quickly.

So-called 'residential' panels are usually 72 cell, and typically output near 40 volts, which is just about right for an MPPT controller WITHOUT having to put ANY panels in series. Want more solar? Just add more panels - even an odd number of them. Done. Residential panels are also often a better buy with regard to dollars per watt, simply because of the volume they are made in. There is zero issue putting them on a trailer. They are robust.

Now, 'residential' panels can be very large, which might make mounting them on some RV's problematic. HOWEVER. While most residential panels have their cells made from 6" silicon ingots, making them at least 39" wide, some are available using 5" ingots, making them about 32" wide. I found these to fit on either side of our a/c quite nicely.

You might want to go through my installation which is detailed here:

1230 Watt Solar Install

The price of residential solar panels is coming down as the popularity of home solar goes up. Residential panels are often 72 cell operating near 40VDC. The more common ones use 6" ingots to produce the panel, making them about 39" wide. A few use 5" ingots, giving a panel that is about 32"...

www.rvforum.net

Frank.

 

[pappi49]

Frank, actually the panels I looked at are residential. From what I can figure they are rated at 275 watts,37 volts and about 7.5 amps. These may not be correct since I tried to find them on the mfg. web site but I think they are close.

I have not yet pulled the trigger on the purchase yet since I am comparing them to some other sites and they seem to be a little high priced. Fortunatly I am in no hurry to get this doen so I can wait.

I am currently putting a list together of components that I think will work and getting some feedbackfrom some of the mfgs.