MPPT controller for 1000W panels

[monte]

Hi, just a quick question for recomendations for an MPPT controller. Im thinking of installing 3/335W sunpower 24V panels to charge my 12V system 840Ah. Best options? One controller would need to be 1000/12=83.3A minimum? or individual controllers for each panel would need to be 30A each minimum? Just wanting to check my math and make sure sizing is right.
Best options for controllers available easily in France...
Merci,
Monte

[colemj]

Controllers are rated by the input, not output, amperage. In your case, a MMPT controller would need to have 42A input (1005W/24V) - which should realistically be a 60A model.

Can't help you with availability in France.

Mark

[Atraxia]

Hi Monte,

We installed individual controllers for each panel (2x250w in our case).
It works great and gives a maximum output. It's worth the extra investment (in my opinion).

[CAELESTIS]

The Midnite Classic 150 would do the job. It handles 96 amps. MidNite Solar Inc. Renewable Energy System Electrical Components and E-Panels

[monte]

I just checked the specs on the panels and they are
Rated Voltage (Vmpp) 54.7 V 54.7 V
Rated Current (Impp) 5.98 A 5.86 A
Open-Circuit Voltage (Voc) 64.9 V 64.8 V
Does that mean the max input is 1005/54.7 = 18.3A ?

I used the morningstar MPPT 60A string calculator and it came up with this (it didnt have the 335W panels so I put in the 315
String Sizing Tool Calculation results

PV Module: Sunpower Corporation - SPR-315-WHT
Morningstar Product: TriStar-MPPT-60
Print Close
System Information
Minimum Battery Voltage 12.00 Vdc
Maximum Battery Voltage 12.00 Vdc
Record Low Temperature 10.0 °C
Record High Temperature 30.0 °C
Configuration
1 Module in Series Per String
3 Strings in Parallel
945 Watts Total
Maximum Nominal Solar Input Power exceeded for this controller. Controller output current will be limited, reducing power harvest below Maximum Power Point levels. Full output of array will not be realized. No risk of damage to controller in this configuration.
Click here for more information
PV Module Specifications
Module Name Sunpower Corporation - SPR-315-WHT
Pmax 315.00 W
Voc 64.20 V
Isc 6.14 A
Vmp 54.70 V
Imp 5.76 A
Voc coefficient -0.280 %V/°C
NOCT 45.0 °C
Array Information
Max. Operating Voc 66.90 < 150 Max. Vin
Min. Vmp 49.31 > 12.00 Vb Max.

Max. Vmp 52.90
Morningstar Product Specifications
Product Name TriStar-MPPT-60
Maximum Battery Current 60.00 A
Supported Nominal Battery Voltages 12V, 24V, 36V, 48V

[monte]

This information sheet is very informative!
http://www.morningstarcorp.com/wp-co...ogy-Primer.pdf
So it would seem I can use the tristar MPPT 60 without cooking it. Probably the best option as I cant imagine seeing 60A going into the batteries very often anyway.
Im sure my last system with 3/180W panels rarely showed much over 30A going in with the same controller...

[monte]

ok, doing some homework before bed, I found the string calculators for the victron 150/85 and it accepts the configuration just, if wired in parallel, but not in series. I guess that shouldn't be a problem.

[downunder]

Have you looked at Outback MMPT controller.

[noelex 77]

Normally solar controllers are rated for the greatest current and voltage that their internal circuitry will manage.

Thus you cannot use a 60A controller with 12v batteries if the solar output is 20A @ 60v, because while the input is lower than 60A the output will be greater.
Therefore with controllers you need to look at the maximum output current at your battery voltage and the maximum input voltage of the solar panels and make sure the controller is rated for more than these numbers. It is the maximum, input, or output that counts.

It also pays to download the manufactures handbook before you finally decide on the model. Sometimes the ratings are only nominal and have to be adjusted for temperature etc. (thus an 80A model can be 80A @20C, but only 70A with an air temperature @35C)

For these large solar arrays the best controllers are from Midnite and Outback.


The Midnite is newer and has some great features, such as a removable display and user software updates.
The Outback is a little more conservative, but very well proven and reliable.

I think you can get slightly more leeway in current handling above 80A with the Midnite model and that would be helpful. It would therefore would be my choice although the Outback will protect itself if the current goes above 80A and in reality you are very unlikely to ever see this.

The Outback 60 is only suitable for a maximum solar array of 800w with 12v batteries, but the Outback 80 will go up to 1250w. (From their handbook). Outback have also released a totally waterproof model which would be great on a boat but I don't know the details and it quite a bit more expensive.

I am less familiar with the current Midnite model range, but if they make a 96A model that would give you a little extra buffer. However check they meet these specifications at higher temperatures. If there is any suggestion that you might increase the solar array in the future go a bit bigger.

The other option is two 60A controllers. This gives you redundancy and slightly better tracking, but the costs of 2x60A models are usually considerably more than one 80A model.

[colemj]

One thing to consider - has anyone ever had their solar array produce the stated output in practical usage? Consistently? Ours sometimes hits that for a short time with low batteries, a clear cooler day and direct overhead sun. Another $600 to meet those rare occasions may not be worth it.

Mark

[SVNeko]

If you want to go with only one controller, you will need one that can handle 3 x the open circuit voltage. The only one I am aware of is the Midnite Classic 200. It is a good one - I know because there is one humming away on my boat right now.

[colemj]

That is only true about the voltage if he is connecting them in series. In parallel, the combined voltage is only that of a single panel.

If your controller is humming, you should get off the boat now…

Mark

[noelex 77]

Originally Posted by SVNeko

If you want to go with only one controller, you will need one that can handle 3 x the open circuit voltage. The only one I am aware of is the Midnite Classic 200. It is a good one - I know because there is one humming away on my boat right now.

Only if you want to wire them in series.
There is a lot of dispute, but the consensus is that parallel connection is better.
(I will run for cover now )

The Voc of the three panels would be 194v which is too close if the maximium voltage rating is 200v (like the name suggests). Unlike current, controllers are usually instantly damaged by voltage over their specs and panels can put out more than Voc on rare occasions.
I seem to remember Midnite advertising that they have some reserve on Voltage damage, so they may be happy with this, but check carefully and don't cut it that fine on most controllers. (Terrible internet at the moment so I cannot download the handbook for the Midnite. Is it 200v?. Do they comment on protection above 200v?)

[noelex 77]

Originally Posted by colemj

One thing to consider - has anyone ever had their solar array produce the stated output in practical usage? Consistently? Ours sometimes hits that for a short time with low batteries, a clear cooler day and direct overhead sun. Another $600 to meet those rare occasions may not be worth it.

Mark

Yes it is only going to happen rarely (although you can briefly exceed the specs in perfect conditions).

This is why an 80A model should be fine (providing there is protection for over current which most models have), but a single 60A model is way too small.

[noelex 77]

I still cannot download the manual,(it is too large for my slow internet) but did manage to find this:
http://www.midnitesolar.com/pdfs/whyHyperVOC.pdf

There is some extra voltage protection on the Midnite range they call it HyperVOC, but my reading of the brief documentation suggests that the 200 is not safe with three panels in series even with this added protection, at least at colder temperatures. The good news if you really want to connect them in series is that there is also a Classic 250 model which would be OK.

I liked this warning in the document. It is tongue in cheek, but it does emphasise the importance of of being very careful about the max voltage to avoid damaging controllers.

"Go to the section of the instructions for your normal (other than MidNite) controller that deals with PV input voltage. It will read something like this regarding voltages above 150V. “Voltage above 150VDC will cause the controller to explode into a huge ball of flames leaving a smoldering crater. This condition is not covered under warranty.”