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DIY solar installation


 Jim McGarvie

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4 hours ago, Ivan K said:

Notice that the ones I bought tested a little higher than 200W, this is why I got them for few extra $ to hopefully get the most from our limited space. Otherwise the price is the same as your source for regular 200W panels, same thing. 

Ivan, from what I can tell, I'm thinking that the "+25%" are the panels with the transparent background (which gives you more electricity if there is scattered light from lighter colored surfaces).  It doesn't seem like they are panels have specifically tested higher.  But I haven't phoned to confirm this, just looking try to figure what the +25% means.  BTW: my panels are 180w with white background, from a couple years ago.

Continuous Resources also sells the +25% models, but they are sold out (and don't mention the price).  https://www.continuousresources.com/collections/solar-panels-and-hardware/products/200w-25-36-cell-12v-nominal-solar-panel-5-busbar

Ivan, do you know any more specifics on what the +25% means?

thanks,
Jason.

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Jason, I am not familiar with the test procedures but I think to remember seeing their YouTube video way back when I was looking at getting the first pair. Anyway, each panel comes with its individual test sheet and they all indicated a little over 200w. (I wish I knew where they got filed away...)I do not expect to get that in real life ever but thought it was worth the few dollars extra. There are 3 pairs for sale right now at his eBay store and you can ask him, he was pretty quick to reply to me in the past through eBay questions.

https://www.ebay.com/itm/2-200-25-Watt-12-Volt-Battery-Charger-Solar-Panel-Off-Grid-RV-Boat-400-25-W/264459865692?hash=item3d93094e5c:g:GMAAAOSwbWZacTa~

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I’ve got two of their panels, and I like them... but hightec solar doesn’t have some kind of advanced physics mojo that nobody else in the industry has. Mine came with test certificates that showed the test was run signIficantly colder than ‘standard’ conditions. 
The construction of the panels is almost identical to my other Grape Solar panels and I think folks buy components on the open market and then just assemble the panels in US. 

Maybe 4-vs-5 bussbars make a difference, but I suspect the mono crystalline cell wafers are a commodity product and all pretty similar. 
cheers

Walter

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14 minutes ago, Jim McGarvie said:

A new question: What are folks using for disconnect switches for their solar panels? Just like our battery disconnect switches?

Thanks.

Jim

 

I found a small battery disconnect switch on amazon that’s rated for 48v. 
Cheers

Walter

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12 hours ago, wamcneil said:

I found a small battery disconnect switch on amazon that’s rated for 48v. 
Cheers

Walter

A bit more info...   I’ve got the battery switch In between the panels and the controller, as a disconnect for the panels pos cable. These wires don’t need overcurrent protection because the panels can’t produce enough amperage to get the wire hot. 
The wires between the controller and the battery need to disconnect AND overcurrent protection, so I’ve got a 90a circuit breaker on the battery end. 
I like the idea of using an AC disconnect for the panels. That’ll break both the positive and neg connections. I believe residential codes for solar require disconnect of both + and  -. Even if the AC disconnect is not ‘certified’ for DC it should be more than adequate for this application. This option didn’t work for me because the box didn’t fit where I wanted the switch to be. 
Cheers

Walter

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11 minutes ago, wamcneil said:

A bit more info...   I’ve got the battery switch In between the panels and the controller, as a disconnect for the panels pos cable. These wires don’t need overcurrent protection because the panels can’t produce enough amperage to get the wire hot. 
The wires between the controller and the battery need to disconnect AND overcurrent protection, so I’ve got a 90a circuit breaker on the battery end. 
I like the idea of using an AC disconnect for the panels. That’ll break both the positive and neg connections. I believe residential codes for solar require disconnect of both + and  -. Even if the AC disconnect is not ‘certified’ for DC it should be more than adequate for this application. This option didn’t work for me because the box didn’t fit where I wanted the switch to be. 
Cheers

Walter

Thanks for the details, Walter.

Jim

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Thanks to help here, I now have the disconnect switch and most other hardware, and I think I have decided on the Hightec 200W panels from Continuous Resources.

But now I'm confused about controllers. I’m planning on four 200W panels, and want to leave provision to add a couple more if necessary. I think I want to wire them in series/parallel, to double the voltage and the amperage. That would give me about 48V and 20A. If I end up adding two more I would put them in series and then parallel to the first two pair, which would give me 48V and 30A.

I understand you can’t exceed the max rated input voltage, so I started looking at 40A controllers, which should be plenty of margin. But I just discovered they specify no more than 520W input from the solar array for 12V batteries. I don’t understand the reason for that and have yet to find the answer googling. Looks like I would have to go to a 60A controller (bigger, heavier, more expensive) to handle 800 or 1200 watts of panels (the 60A unit is supposed to be good for 1225W at 12V).

I’ll certainly spring for the 60A if necessary, but seems like overkill. Is that input wattage limitation really a thing?

Thanks for the help!

Jim

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In ideal conditions, your 800W would produce 57A down to the batteries at roughly 14V charging voltage. That's more than 40A controller should do. Having said that, I have this setup but in series and no ideal conditions expected. Might have to upgrade eventually.

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35 minutes ago, Ivan K said:

In ideal conditions, your 800W would produce 57A down to the batteries at roughly 14V charging voltage. That's more than 40A controller should do. Having said that, I have this setup but in series and no ideal conditions expected. Might have to upgrade eventually.

Thanks for the reply, Ivan, but I'm a bit confused. I was planning a series/parallel install. Two sets of two panels in series, sets connected in parallel. The panels I am looking at have a Voc of 24V and Isc of 10A. So each pair of panels in series would be 48V and 10A. The two pair paralleled would be 48V and 20A. Right? What am I missing?

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I wish I was wrong but the controllers amperage size applies to the downstream current after conversion from PV (solar) power to the 12V (or whatever charging stage voltage) down to the batteries. Like your 800W PV expectation will convert to 66.6A at 12V from controller to batteries, in theory. In other words, you would feed the batteries with 66.6A as opposed to the controllers 40A rating. 66.6A x 12V ~ 800W.

It does not matter parallel or serial, it's the total power (W) that converts to amperes at battery voltage.

Maybe it makes more sense to say that the Amp rating is referencing max output current of the controller?

Edited by Ivan K
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18 minutes ago, Ivan K said:

I wish I was wrong but the controllers amperage size applies to the downstream current after conversion from PV (solar) power to the 12V (or whatever charging stage voltage) down to the batteries. Like your 800W PV expectation will convert to 66.6A at 12V from controller to batteries, in theory. In other words, you would feed the batteries with 66.6A as opposed to the controllers 40A rating. 66.6A x 12V ~ 800W.

It does not matter parallel or serial, it's the total power (W) that converts to amperes at battery voltage.

Maybe it makes more sense to say that the Amp rating is referencing max output current of the controller?

OK, I think I understand. Thanks Ivan.

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Keep in mind, the 200w panels will not actually produce 200w except on a really bright, clear and COLD day with the sun at 90 deg to the panels. You’ll probably get more like 40-45 amps out the controller with 4 panels. 
You’ll need to check the controller specs, but it should be ok to have more capacity in the array than the controller can output; it’ll just throttle back to its rated output whenever the panels exceed its capacity. 
If you’re wanting to add 2 more panels, I’d go for a 60+ amp controller now. Dual controllers are certainly an option, but will require running more wire down from the roof. 
Cheers

Walter

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1 hour ago, W7BE_Bob said:

If the specs don't allow you to over panel for watts or amps then don't. 

A future second controller is a option. 

Good advice in general I think, Bob. I've admired your installation in the past. I looked up your controller and it appears to be rated at only 800 watts input, versus the 1225W of the Epever Tracer I'm considering. But the specs on yours say: "*Input power can exceed Nominal Operating Power. Controller will limit and provide its rated continuous maximum output current into batteries." And I don't see that statement on the Epever. Maybe that's why yours costs twice what the Epever does.

I wonder whether all MPPT controllers have that over-panel capability

10 minutes ago, wamcneil said:

Keep in mind, the 200w panels will not actually produce 200w except on a really bright, clear and COLD day with the sun at 90 deg to the panels. You’ll probably get more like 40-45 amps out the controller with 4 panels. 
You’ll need to check the controller specs, but it should be ok to have more capacity in the array than the controller can output; it’ll just throttle back to its rated output whenever the panels exceed its capacity. 
If you’re wanting to add 2 more panels, I’d go for a 60+ amp controller now. Dual controllers are certainly an option, but will require running more wire down from the roof. 
Cheers

Walter

Thanks Walter. Makes sense to me. I will go for a 60A controller.

Jim

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40A is the output to the battery. Choose a battery charging voltage like 14.4V. 800/14.4 = 56A to the battery. This is ideal sun and no losses. What will your 40A controller do with 56A?

Voc is only used to insure that the panels don't exceed the max input rating of the controller, it's not used for power calculations. 

MPPT = Maximum Power Point Tracking. For MPPT controllers use the panel spec Imp and Vmp (maximum power).

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11 minutes ago, W7BE_Bob said:

40A is the output to the battery. Choose a battery charging voltage like 14.4V. 800/14.4 = 56A to the battery. This is ideal sun and no losses. What will your 40A controller do with 56A?

Voc is only used to insure that the panels don't exceed the max input rating of the controller, it's not used for power calculations. 

I will probably never see the full 800 watts. For one thing, I live in North America, and I will not have tilting panels. I "assumed" the controller would handle excess power from the panels much as it treats excess voltage over and above charging voltage. But you know what they say about assumptions.

And yes, I understand Voc.

Thanks so much for the continuing education!

Jim

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1 hour ago, Jim McGarvie said:

Thanks for the reply, Ivan, but I'm a bit confused. I was planning a series/parallel install. Two sets of two panels in series, sets connected in parallel. The panels I am looking at have a Voc of 24V and Isc of 10A. So each pair of panels in series would be 48V and 10A. The two pair paralleled would be 48V and 20A. Right? What am I missing?

Jim, I think other people have stated it as well, but just to reiterate that the MPTT controllers will take the 48v/20A going into the controller will still convert to 12V/40A going to the batteries (technically 13.6v and whatever amps, but you get the gist).

Look at controllers that can be extended in parallel.  I've got one of the BlueSky 3024i controllers (also purchased from Continuous Resources), and plan to add a second controller with new panels.  They can be networked together so they can manage and report together.  That also gives you the option to mix and match panels in your overall system (my first install has 180w panels to the first controller, the next one will have 200w panels).  If you go with one big controller (60A or larger) you may run into challenges trying to figure out how to best combine mismatched panels.

Many ways to solve this problem, just adding another option, hope this helps,

Jason.

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The stated 540W limit helps to ensure that the controller specs are not exceeded over a wide range of light and temperature. And can also limit warranty claims. 

I generally use 67% of the panel watts for 4-5 hours for planning purposes with my flat panels. 

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Jim, I'm sure you are going with an MPPT controller.  That said, running running 40+ Amps off the roof for 800 Watts is ridiculous in my opinion.  Maybe that would be acceptable with the old tech PWM controllers.  In you case I would run 3, or even 4 in series.  I believe that Open Circuit Voltage (the absolute voltage that could be produced with no current draw - a design parameter more than functional) is 24.335 Volts.   That is only 97.34 Volts absolute maximum that you controller could possible see in a theoretical situation.  The voltage you'll see is more likely 24.052 or less (Voltage-Max Power).  So that would be 96.208 Volts.  Most all MPPT Controllers will handle at least 100 Volts - if they don't, move on to the next.  By running all 4 in series, the current in the wire from the PV array on the roof down to the MPPT controller would be max 9.87 (short circuit current) and more likely less than 9.5 on a clear, cool day with the sun directly overhead.  You are familiar with the current vs wire size tables, and I'm sure you can see that you'll be able to use a much more manageable size wire off the roof.  Remember the beauty of the MPPT controller is it doesn't care what combo of voltage/current you hit it with, it will use what it gets to the maximum benefit.  An additional benefit is that you don't have to wait until the sun rises high enough to produce 15-16 volts before charging can begin.  By wiring in series you get that when each panel is only producing about 4 volts each, not near enough to charge a 12 volt battery.  The down side is that if you got old panels without blocking diodes, shading on one panel can adversely affect the total system.  But, and reputable manufacturer in the last 5 -10 years has automatically built this diodes into their array.  As far as future expansion, you and over-buy now, and then if you add 2 more panels, run two runs of 3 down from the roof (74 Volts @ 9.5 Amps each) and input each to it's own controller.  That would require you to buy a second controller in the future.  Or, you could parallel the two - three panel runs, and make sure you plan on wires from the roof to your big controller that would handle 19 Amps.  Of course, this means you'll have to purchase a larger controller off top.

Regarding controller power, as other have said, it's the power going to the battery that the ratings are based.  You really don't need to care what the combination of voltage/current that makes up the power - the controller doesn't care - as long as the overall specs are not exceeded.  Many controller will do exactly what you hinted at.  I'm not sure if it is the controller in my current Exec (the Red coach) or the one in my previous Dynasty (the Blue coach), but I called and talked to the engineers, and was told that one the max power was reached, the controller would simply discard the potential addtional current.  Remember you don't force current, it is based upon what the load will draw.  You can't put more current into the controller than it wants.  That is NOT true with voltage.  So, if you ended up with a great day of sun and clear skys in the middle of the summer, as long as the voltage didn't exceed the max for the controller, it would just us the current up to the power it's rated at (I'm not sure if that rating is before or after internal losses, but who really cares?).  I think I used Renogy for my controller in the Dynasty, and I'm using two Victron MPPT 100/50 (100 Volts/50 Amps) in my Exec.  One reason is that the previous owner had already installed one.  So when I added more panels, I wanted to keep the system intact so my Battery Power Meter would register all the solar.  Note that the 50 Amps (@100 Volts) is only good if you have 24 Volt system.  On a 12 Volt system, it's only rated at 700 W.  

Have you sorted the way to get your cables off the roof and to the controller?  BTW, the controller should be located as close to the batteries (or inverter) as possible.  That is because you may see well over 40 Amps on that cable, and running big cable is not only expensive, but a real task to just route and bend.  If you are still looking for examples of getting the cable from the roof to the basement, let me know and I'll try and take some pictures of mine.  It has 1-1/2" PVC running from the basement all the way to the roof.  On the roof is a 8x8 or maybe 10x10 PVC Junction box, where all the panel cables, along with WiFiRanger antenna come together.  Those that are paralleled are done so inside this box.  Then they drop all the way to the compartment where my electrical and water hose are.  From there, they run across the basement ceiling, under the plastic ceiling sheet, to the bay where the inverter is connected to the batteries with the huge cable (00 or 0000, not sure).  I used the same terminal strip to connect the controllers.  My rationale is if that cable can supply enough current for the inverter (mine is 3000 Watt PSW), then it can handle the current from the solar.

Let me know if you have any questions.

 -Rick

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Rick - Some Comments

Voc increases with decreasing temperature. My panels are about 8% higher at 32F. A controller with a 100V limit would not be wise for your example of 4 panels in series. For bulk and abosrb charging Imp is used. The controller may default to Isc for absorb charging. Your text is referring to bypass diodes not blocking diodes. All controllers prevent panel drain at night which was the purpose of blocking diodes. Lots of good information in your post.

My 3 series panels have 62' (includes panel pigtails) of 10ga UV wiring. Wiring is held in place with dabs of Dicor. Monacos inside cabinet panels are cosmetic, connected with brads and glue. I removed some to run the vertical solar wires and reattached with some screws - Out of sight. The wires got to a A/C 240V disconnect switch and then the controller. The controller has a short run of 4ga wire to the inverter which has a long run of 4/O wire to the batteries another poor electrical choice by Monaco.

 

 

 

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2 hours ago, waterskier_1 said:

Hi Rick, good to hear from you!

Jim, I'm sure you are going with an MPPT controller. 
Absolutely!

That said, running running 40+ Amps off the roof for 800 Watts is ridiculous in my opinion. 
I would agree. But I wasn't planning on doing that; I was planning on two sets of two, series/parallel. Unless my calculations are wrong the four 200W panels wired that way would only be 20A. Even if I add another parallel string of two in series, that would be only 30A. Right?

Maybe that would be acceptable with the old tech PWM controllers.  In you case I would run 3, or even 4 in series.  I believe that Open Circuit Voltage (the absolute voltage that could be produced with no current draw - a design parameter more than functional) is 24.335 Volts.   That is only 97.34 Volts absolute maximum that you controller could possible see in a theoretical situation.  The voltage you'll see is more likely 24.052 or less (Voltage-Max Power).  So that would be 96.208 Volts.  Most all MPPT Controllers will handle at least 100 Volts - if they don't, move on to the next.
Your comments make me think I should consider wiring all 4 panels in series. The top controller on my list (so far; I am still open to suggestions) is the Epever Tracer 6415AN, a 60A controller with a max input of 138V, so that would easily run 4 or 5 in series. And as you say I think just about any controller I would consider could handle that. I was initially concerned with the affect of shadows with an all-series arrangement, but as you pointed out, any panels I would buy now have the bypass diodes to help compensate for that.

Have you sorted the way to get your cables off the roof and to the controller? 
I need to check a little further, but I think I can run mine the way I've read a few others have wired their Monacos: down through the rear cap. I have a junction box with a terminal block I plan to secure to the top of the rear cap with a hole through the bottom of the box and roof of the rear cap. The wires will go from there directily into the rear curbside compartment, which is where the inverter/charger is located.

BTW, the controller should be located as close to the batteries (or inverter) as possible.  That is because you may see well over 40 Amps on that cable, and running big cable is not only expensive, but a real task to just route and bend. 
My controller will be mounted a few inches from the inverter/charger, and connected to the inverter/charger battery terminals by just a couple of feet of 4ga.

Thanks for all the input, Rick. Hope to see you and your dad at Quartzsite again in January.

Jim

 

 

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