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Old 02-10-2015, 11:21   #1
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Solar panel/ MPPT controller system design

Question, because I havent found a really good source on marine solar system design. I'm stuck on a solar system design issue.

I'm planning on installing approx 500watts of panels between the aft davits and the hard dodger. I've decided fto use 5 x 100watt panels to combat the inevitable shadowing issues with having a ketch rig. I've spec'd out the design 2 ways

2 arrays 1 x 300watt and 1 x200watt with 1 large 40 amp MPPT controller. this puts the combined output (with switches to isolate) at almost the max output of the controller.

2 arrays 1 x 300watt with 1 30amp MPPT controller and 1 x200watt with 1 20 amp MPPT controller. This gives me reserver space for potentiallty adding a bit more solar if needed but increases the cost and complexity.

what is the preferred way to set this up? The panels will be flat, permanently mounted and not tracking the sun in any way. Will the Controllers conflict with each other reading the battery voltage?
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Old 02-10-2015, 11:32   #2
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Re: Solar panel/ MPPT controller system design

I asked this question in the past and posted an article on how it works.

The TLDR version: There is no problem running 2 controllers, they will not interfere, but you should keep the same brand.

If it was me, I would also run your panels in series so you could get away with smaller gauge wire.

P.S. Running 2 controllers adds redundancy. If a controller dies, you only loose part of your array!
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Old 02-10-2015, 11:41   #3
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Re: Solar panel/ MPPT controller system design

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Originally Posted by travellerw View Post
I asked this question in the past and posted an article on how it works.

The TLDR version: There is no problem running 2 controllers, they will not interfere, but you should keep the same brand.

If it was me, I would also run your panels in series so you could get away with smaller gauge wire.

P.S. Running 2 controllers adds redundancy. If a controller dies, you only loose part of your array!

Thanks. I considered running them in series for that same reason, but if one panel gets shaded (in series) it drastically affects the output of the other 2. How have you handled this? Got a link to your article? I do like the redundancy idea ( just not the cost associated with it!)
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Old 02-10-2015, 11:59   #4
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Re: Solar panel/ MPPT controller system design

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Thanks. I considered running them in series for that same reason, but if one panel gets shaded (in series) it drastically affects the output of the other 2. How have you handled this? Got a link to your article? I do like the redundancy idea ( just not the cost associated with it!)
No thats not true for MPPT controllers. If one panel gets shaded, then the voltage drops and the MPPT does its thing to find the "Maximum Power Point". There is only a real problem when 2 panels get shaded and the voltage drops below about 14v or so.

Here is the article I posted on another forum.
Parallel Charging Using Multiple Controllers With Separate PV Arrays » Morningstar Corporation

P.S. I use new Tracer series controllers from China. They are well built and very affordable ($100/20A $130/30A). One has been on my boat all summer in +40-50 heat and is still pumping out the amps!
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Old 02-10-2015, 12:05   #5
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Re: Solar panel/ MPPT controller system design

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No thats not true for MPPT controllers. If one panel gets shaded, then the voltage drops and the MPPT does its thing to find the "Maximum Power Point". There is only a real problem when 2 panels get shaded and the voltage drops below about 14v or so.

Here is the article I posted on another forum.
Parallel Charging Using Multiple Controllers With Separate PV Arrays » Morningstar Corporation

P.S. I use new Tracer series controllers from China. They are well built and very affordable ($100/20A $130/30A). One has been on my boat all summer in +40-50 heat and is still pumping out the amps!

Thanks. Are you using the new Tracer BN series or the new, new A series? I haven't yet found anything online reviewing the A series.
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Old 02-10-2015, 12:24   #6
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Re: Solar panel/ MPPT controller system design

BN series. If you search my username, I posted a teardown.


I have 1 20a being driven by a 300W array. It has survived for months.
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Old 02-10-2015, 12:42   #7
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Re: Solar panel/ MPPT controller system design

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BN series. If you search my username, I posted a teardown.


I have 1 20a being driven by a 300W array. It has survived for months.
I'll have a look. isn't 300w over driving the 20a model? its only rated at 260w
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Old 02-10-2015, 13:44   #8
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Re: Solar panel/ MPPT controller system design

TravellerW what do you think of this new version : 12V 24V New Tracer 4210A 40 amps MPPT Solar Charge Controller 40A Boost EP solar made EPEVER brand-in Solar Controllers from Electrical Equipment & Supplies on Aliexpress.com | Alibaba Group
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Old 02-10-2015, 14:03   #9
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Re: Solar panel/ MPPT controller system design

You really can't tell until you actually take them apart and observe the engineering and component quality.

I'm guessing that due to the lower price, that controller is a completely different design then the BN series. I'm also guessing it has much lower quality components.

Thats what I liked about the BN. It uses all brand name components inside. Many of the components were made in Japan and USA.

It really depends how tight your budget is and how willing you are to gamble. I gambled on the BN when I bought it, and it has paid off. Now I own 4 of them!
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Old 02-10-2015, 14:04   #10
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Re: Solar panel/ MPPT controller system design

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I'll have a look. isn't 300w over driving the 20a model? its only rated at 260w
Yes.. and it has taken that abuse for over 6 months in the tropics.
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Old 02-10-2015, 14:18   #11
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Re: Solar panel/ MPPT controller system design

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Yes.. and it has taken that abuse for over 6 months in the tropics.
Do you have a link to where I can get that controller at a good price?
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Old 02-10-2015, 14:25   #12
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Re: Solar panel/ MPPT controller system design

I bought 3 from this seller...

Tracer2215BN MPPT 20A 150V professional grade die cast aluminum design for home system, outdoor lighting, signals, RVs and boats-in Solar Controllers from Electrical Equipment & Supplies on Aliexpress.com | Alibaba Group

I also bought one display panel from someone on AliExpress for $30. I can't find the seller now though!
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Old 02-10-2015, 14:29   #13
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Re: Solar panel/ MPPT controller system design

Thank you
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Old 02-10-2015, 14:57   #14
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Re: Solar panel/ MPPT controller system design

Your pannels will inevitabley be part shaded. If you wire in series you will loose a lot. Panels shoud be purchased if possible with multiple diodes internal to bypass partially shades parts of a panel. Panels in parallel will need diodes if they are not already so equipped. Only if you can guarantee no partial shading should you wire in series.

I found that I cold buy 2-pole breakers on Amazon that would double as switches. This eliminates fuses and switches. Each panel has its own 2-pole breaker with wires run from each panel to the interior of the boat there the breakers are located. The panels are then combined on a large junction block into two high amp lines to the charge controller. The charge controller output has its own 2-pole breaker. The 2-pole breakers let us isolate all of the solar stuff in an electric storm or for work.
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Old 02-10-2015, 15:26   #15
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Re: Solar panel/ MPPT controller system design

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Your pannels will inevitabley be part shaded. If you wire in series you will loose a lot. Panels shoud be purchased if possible with multiple diodes internal to bypass partially shades parts of a panel. Panels in parallel will need diodes if they are not already so equipped. Only if you can guarantee no partial shading should you wire in series.

I found that I cold buy 2-pole breakers on Amazon that would double as switches. This eliminates fuses and switches. Each panel has its own 2-pole breaker with wires run from each panel to the interior of the boat there the breakers are located. The panels are then combined on a large junction block into two high amp lines to the charge controller. The charge controller output has its own 2-pole breaker. The 2-pole breakers let us isolate all of the solar stuff in an electric storm or for work.
There are many many posts on here in regards to series vs parallel. Its a deep and complex subject.

The statement that you "will loose alot" in series with an MPPT controller simply isn't true. I tried both configs on my boat and did not see a significant difference either way. I tried shading the panels in both configs.

In the end, I prefer less runs of smaller gauge wire at higher voltage. My one array is running at 80V and this allows me to use a much smaller guage of wire.
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