Solar panels / charger doing what it is supposed to?

[Kevin D Pem]

Because you asked @Neal my system is based on 60 amp controllers.

Why you ask??
A 60 amp controller will handle 720 watts of panel at 12v, 1440w at 24v. This means I have back-up if failure occurs. I know that is my sailor mentality, but just the same! Sometimes controllers are a week or more away.

But there is a better reason to use smaller!!! Because he who dies with the most toys wins!!! OK, just kidding. Shading just one cell on a panel kills the power of the whole panel. Well I have more bad news. The complete system can be compromised. Imagine back feeding one cell with your entire 1800 watts!!!

So where a possibility of Shading is present, I have split the power between several controllers. I have 4 controllers in my system.

More directly because Shading is such a big issue on a RV, many smaller controllers are the way to go!!! And yes 100 amp Controllers would do the job, smaller will also do the job at a lower overall cost.

 

[Joe Hogan]

We had around 12-1300w of solar installed and mid day could generate 1100 or so watts to the battery. We opted for a higher voltage configuration to avoid overheating the pre installed Newmar solar prep wires.
As you can see we easily exceeded 75amps to the batteries.

 

[Kevin D Pem]

We had around 12-1300w of solar installed and mid day could generate 1100 or so watts to the battery. We opted for a higher voltage configuration to avoid overheating the pre installed Newmar solar prep wires.
As you can see we easily exceeded 75amps to the batteries.

View attachment 19104

Wow, those are exceptional numbers! Because I don't have the charts in front of me. A 100a controller is rated for ?1360? Watts of panel at 12v?

 

[Rich W.]

You can always run two with a second string of panels.

 

[Kevin D Pem]

You can always run two with a second string of panels.View attachment 19119

Yah, you can even run different sizes panels on the second controller with no issues.

 

[Rich W.]

Yah, you can even run different sizes panels on the second controller with no issues.

I hadn’t thought of that. I just run two 315s on one string and three on the other. I also ran 14ga for my panels and abandoned the factory 6ga “solar prep”. One of the benefits of residential panels.

 

[Kevin D Pem]

I hadn’t thought of that. I just run two 315s on one string and three on the other. I also ran 14ga for my panels and abandoned the factory 6ga “solar prep”. One of the benefits of residential panels.

Yah I use 10awg, with two panels in series. On the roof wires. Still running 6awg from the cargo panels. Less losses.

 

[Rich W.]

Yah I use 10awg, with two panels in series. On the roof wires. Still running 6awg from the cargo panels. Less losses.

Panels are 33v, 9a so not much loss. Another benefit of residential panels. I like the idea of filling in with a string of smaller panels on another controller (I have one more 150/35 in stock) - maybe some 200w or so panels where my 315s wont fit. I could probably add another 600w pretty easily.

 

[Kevin D Pem]

Panels are 33v, 9a so not much loss. Another benefit of residential panels. I like the idea of filling in with a string of smaller panels on another controller (I have one more 150/35 in stock) - maybe some 200w or so panels where my 315s wont fit. I could probably add another 600w pretty easily.

Like I said. I use 60 amp controllers. I can keep the numbers in my head for easy access. I have both 24 and 12 volt system. This means having the numbers in my head and consistent equipment keeps me from making as many mistakes. But a good understanding of the equipment makes for a mix and match environment.
I think you're on your way!!!

My panels are used 240 and 250w panels they are 60 cell panels as are yours. Mpp is 29.? Or 30.0 as I recall. That of course is charge voltage for lead acid, so no room for a cloudy day. So I run 2 panels serial to get 60 v mpp. My controllers will handle??? Higher voltage than the open voltage so that works reliably. The cavit is an mppt controller is a smart buck converter, and that means for efficiency the voltage in vs. out, should be limited to 2.5 times. 40 v in 15 out. So when I work on my 12 volt system the array is paralleled 30 in 15 out. Everything including wire needs to handle the loads at minimum loss. Because my system is built for redundancy in case of a failure, all such components have to work on 12 volts, reliably.

Did you know that if you have a house panel (affectionately called a 24v panel) and a 12v panel, if the cell size is the same on both panels you can tie them together in series??? Just gave you another answer for limited real-estate.

 

[Rich W.]

I toy with the idea, but for what I do my current system is basically enough - 1575w gives me a nice capable battery charger and on this rig thats all it is. On my Bay Star the solar was a little more involved and would run an AC all day and then on the battery bank (Li-ion) for around 8 hours after sundown. That was nice but in hot climates not enough, and to double that meant a much bigger battery bank. I chose to just stay out of hot weather and reduce my boondocking aspirations.

Pics are the inverter and battery in my Bay Star. Before that I had almost 2kw of solar on an old Class C (there wasn’t as much other stuff on the roof).

This was from the class C with all this equip stuffed below the two dinette seats (the other side was all battery). I charged the battery bank to 32.8 but the 24v inverter would only go to 28v so the balance could only be made up by solar. I enjoyed that system but these days I’d rather just keep it simple. Also the “quiet diesel” generator on my current rig is much more tolerable than the old Onan.

This is with an AC running while charging the battery bank at 17.9a on solar only - no grid power.