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Old 02-05-2021, 11:24   #1
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Solar Controller for 1200 watts

Planning to install 1200 watts of solar on my flybridge hardtop. My battery bank is a 12v system.

Looking for recommendations for the solar controller. Are people using multiple small/cheap controllers or 1 big/expensive controller? I see Victron has a 150v/100a for $785 on amazon. Are there any cheaper brandss in that capacity?
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Old 02-05-2021, 12:47   #2
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Re: Solar Controller for 1200 watts

For redundancy and ease of installation, re: wire size, I'd use multiple controllers with that much solar.

A lot depends on how far you have to run the wires from panels to controller, then from controller to the batteries, and wattage of the individual panels, but you could be looking at 4/0 wire size if you only use a single controller.
Amazon has this 40amp Mppt Controller for $145. You could put in 3 @ 400w each and save some $ over one much larger one, and use MUCH smaller wire.
For reference, I have 1 pair of 6 awg wires for my 380 watts, and it runs about 12 ft from the panels to the controller.
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Old 02-05-2021, 13:41   #3
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Re: Solar Controller for 1200 watts

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Originally Posted by ForeverDes View Post
For redundancy and ease of installation, re: wire size, I'd use multiple controllers with that much solar.

A lot depends on how far you have to run the wires from panels to controller, then from controller to the batteries, and wattage of the individual panels, but you could be looking at 4/0 wire size if you only use a single controller.
Amazon has this 40amp Mppt Controller for $145. You could put in 3 @ 400w each and save some $ over one much larger one, and use MUCH smaller wire.
For reference, I have 1 pair of 6 awg wires for my 380 watts, and it runs about 12 ft from the panels to the controller.
With a 150v/100a controller, i could series parallel 2 groups of 600w. It would be approx 120v/5a each. At that voltage I could use #16 wire from panels to controller. It would just be controller to batteries where I would need something like 2/0. So i'm not sure if there would be much savings on wire, but it would save about $300 for controller.

Are there any issues with multiple controllers confusing each other? Loss of efficiency?
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Old 02-05-2021, 14:03   #4
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Re: Solar Controller for 1200 watts

If you have any shading problems, multiple controllers will minimize the losses. They don't confuse each other.
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Old 02-05-2021, 14:19   #5
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Re: Solar Controller for 1200 watts

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With a 150v/100a controller, i could series parallel 2 groups of 600w. It would be approx 120v/5a each.

Are there any issues with multiple controllers confusing each other? Loss of efficiency?

My very limited experience with mppt controllers is they have a "range" of acceptable voltage inputs for each nominal output. For instance, 12v output will require 12v-20v input, and any higher voltages makes it "jump" to 24v nominal output. I expect the toroidal transformers aren't capable of stepping 120v all the way down to 12v. The controller you are considering may be different, though, but it's something to consider. Could you post a link for the controller? I'd be interested to see what it's capable of.

I've never used multiple controllers, but it's very common, especially with larger arrays like you have in mind. I don't see why there would be any loss of efficiency, amps in is amps in, after all, and as long as they have their settings matched, I can't see why there would be any confusion.
Using 3x40amp controllers @$145 each you'd save ~$350 over the 150v/100amp controller, and I'd be willing to bet you'd break even or possibly save on smaller wires with the triple setup as well.
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Old 02-05-2021, 16:27   #6
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Re: Solar Controller for 1200 watts

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My very limited experience with mppt controllers is they have a "range" of acceptable voltage inputs for each nominal output. For instance, 12v output will require 12v-20v input, and any higher voltages makes it "jump" to 24v nominal output.
Most definitely not true for the Victron MPPT regulators. The "150" in the nomenclature mentioned indicates the maximum input voltage. One can select 12 or 24 v output.

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Old 02-05-2021, 16:30   #7
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Re: Solar Controller for 1200 watts

for 1200w i'd be using at least 3 controllers. much more efficient, and they are not expensive

imho victon are the best brand, and have a wide range of sizes

definitely mppt

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Old 02-05-2021, 16:49   #8
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Re: Solar Controller for 1200 watts

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My very limited experience with mppt controllers is they have a "range" of acceptable voltage inputs for each nominal output. For instance, 12v output will require 12v-20v input, and any higher voltages makes it "jump" to 24v nominal output. I expect the toroidal transformers aren't capable of stepping 120v all the way down to 12v. The controller you are considering may be different, though, but it's something to consider. Could you post a link for the controller? I'd be interested to see what it's capable of.

https://www.amazon.com/dp/B07FCRZ3F6...ing=UTF8&psc=1
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Old 02-05-2021, 16:59   #9
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Re: Solar Controller for 1200 watts

Or, if shading isnít an issue, parallel the panels. Then the resulting 100-120V can travel on relatively small wires to your controller, which you can mount right next to your positive charge bus next to your batteries. Long run at 120V, very short run at 14V. This is what we have done with 3x 330W panels on our davits, 20m wire run to our house bank. We have a Victron 150/100 controller that spits out up 110A at 14.4V - no point having that travel very far.

The higher voltage of the paralleled panels also mean you are more likely to have an active controller earlier in the morning and later in the evening by keeping the panel output voltage as high as possible.

Of course, if shading is an issue then panels in series or individual are more efficient and you can use smaller and relatively cheaper controllers. When we put panels on our new bimini we will split them by side, and parallel them on each side, so two more controllers.

Iím not sure the redundancy argument holds water as multiple controllers add multiple points of failure, but with name brand equipment failure over time is not that big a risk.
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Old 02-05-2021, 18:47   #10
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Re: Solar Controller for 1200 watts

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Originally Posted by Jim Cate View Post
Most definitely not true for the Victron MPPT regulators. The "150" in the nomenclature mentioned indicates the maximum input voltage. One can select 12 or 24 v output.

Jim
Good to know! I'll definitely keep this in mind for future endeavors.

My bad, sorry for the incorrect info! Looks like the controller will do as you expect.
So if redundancy isn't important to you, and shading isn't likely to cause much trouble, your plan ought to work.

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Or, if shading isnít an issue, parallel the panels. Then the resulting 100-120V can travel on relatively small wires to your controller, which you can mount right next to your positive charge bus next to your batteries. Long run at 120V, very short run at 14V. This is what we have done with 3x 330W panels on our davits, 20m wire run to our house bank. We have a Victron 150/100 controller that spits out up 110A at 14.4V - no point having that travel very far.

The higher voltage of the paralleled panels also mean you are more likely to have an active controller earlier in the morning and later in the evening by keeping the panel output voltage as high as possible.

Of course, if shading is an issue then panels in series or individual are more efficient and you can use smaller and relatively cheaper controllers. When we put panels on our new bimini we will split them by side, and parallel them on each side, so two more controllers.

Iím not sure the redundancy argument holds water as multiple controllers add multiple points of failure, but with name brand equipment failure over time is not that big a risk.
Unless I misunderstand completely, I think you mean series the panels to be able to run smaller wires from the panels. Series increases voltage, parallel increases amps. But regardless it sounds like you've had good experience with a similar set up.
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Old 02-05-2021, 21:05   #11
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Re: Solar Controller for 1200 watts

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Good to know! I'll definitely keep this in mind for future endeavors.



My bad, sorry for the incorrect info! Looks like the controller will do as you expect.
So if redundancy isn't important to you, and shading isn't likely to cause much trouble, your plan ought to work.



Unless I misunderstand completely, I think you mean series the panels to be able to run smaller wires from the panels. Series increases voltage, parallel increases amps. But regardless it sounds like you've had good experience with a similar set up.

Yes, series increase voltage and parallels increase amperage. I got that backwards on our panel setups - our davits panels are series wired.

Parallel wiring is better for shading issues.
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Old 03-05-2021, 13:25   #12
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Re: Solar Controller for 1200 watts

1200w ? You don't say how big is your battery bank.
Better be very big otherwise you're wasting money not only on cables as said before but also on MPPT and solar panels !

You need to balance consumption, production and storage.
Consumption:
How much energy you need for a day ?
How many days without sunshine do you want to survive without cranking the engine or the generator ?
Do you have other sources adding to the production ?
These give you how much storage you need.

How quickly you want to charge your battery bank gives you the size of your panel array.

Personal rule of thumb, for a 1200w solar array you need at least 1200 Ah of battery bank.
If you don't, it will be full sometimes during the day and the MPPT will shutdown the array but you're may be still lacking energy before the night is gone...
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Old 03-05-2021, 13:49   #13
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Re: Solar Controller for 1200 watts

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Originally Posted by SKMT View Post
Planning to install 1200 watts of solar on my flybridge hardtop. My battery bank is a 12v system.

Looking for recommendations for the solar controller. Are people using multiple small/cheap controllers or 1 big/expensive controller? I see Victron has a 150v/100a for $785 on amazon. Are there any cheaper brandss in that capacity?
I built my own MPPT for $9 but it's 10 amp maximum. It would cost about $16 to make it 30 amp.
http://github.com/seandepagnier/mppt

The idea is to use multiple controllers, however with enough solar that mppt advantage is not needed, you can just plug your solar directly to the battery without a controller.


This works just fine, as the battery BMS cuts off the charging input when the voltage is high enough. This is ok and good for most lithium battery systems to use solar without a charge controller.
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Old 03-05-2021, 13:53   #14
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Re: Solar Controller for 1200 watts

No charge controller? You doing that right now?
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Old 03-05-2021, 13:56   #15
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Re: Solar Controller for 1200 watts

When I built my Solar panel array, 2 x 300W panels, both the supplier of the panels and the electrician who did the final work adamantly insisted on Victron mppt controls, one for each panel. Reasons: keep the wire size down to reasonable levels, had to fish the wires through the Arch/Davits structure, and for total reliability, one side goes down, the other is still working till you can get parts to fix.

I am very pleased with the performance of the Victron mppt controllers over 2 years now, and the panels live up to their reputation for quality production in less than ideal situations, partial shading and cloudiness.

As noted above you must run an electrical load calculation and battery sizing calculation to insure you have enough capacity to last through a normal night.

Hope this helps,

Apollo Wayne

PS. I would never recommend running panels w/o controllers, very high risk of battery harm & fire hazard.
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