question

chyk101 avatar image
chyk101 asked

What is the maximum number of 300watts solar panels in series on a victron 250/100 Smartsolar Charge controller?

Hello,

I am about to change my charge controller to a victron 250/85 smartsolar charge controller. I would like as high a voltage as possible going into the controller. I intend to connect 6 300w solar panels in series on the charge controller. 2 strings will then be connect in parallel for 12 panels in total. VMP of the panels is 38.80V, VOC is 44.16 and ISC is 8.93A.


Is this a safe arrangements or should I reduce panels in series to 5?

smart solar set-up help
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4 Answers
JohnC avatar image
JohnC answered ·

Hi. 6 is too many. 5 should be ok, but check the Voc temp characteristics of the panels for your climate.

If you're really set on 12x 300W panels, 4 strings of 3x into a 150/100 would work fine.

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chyk101 avatar image chyk101 commented ·

Thank you

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Pat Davitt avatar image
Pat Davitt answered ·

I assume you are feeding a 48V battery system. So at 3600W you will be feeding about 75A to the batteries. Six of the panels in series at 44.16VOC is about 264V, beyond the capacity of your controller. To maximize power production I would use 3 strings of 4 panels in series. This will keep your voltage within limits.

Pat

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Mikael avatar image
Mikael answered ·

I use this to calculate. Just add your modules under under the modules tab.

(v3.1) - VE MPPT Calculator


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chyk101 avatar image
chyk101 answered ·

Thank you everyone. If I go as high as 20 panels, can I comfortably do 5 panels in series for a total of 4 strings? The idea behind having a 250V charge controller is to go as high as possible in series so the charge controller wakes up early and goes to sleep late. I will also be feeding a very large bank and fully off grid.


So, is 5 panels in series a good idea?

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JohnC avatar image JohnC ♦ commented ·

Yes. It should beat your local roosters..

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Pat Davitt avatar image Pat Davitt commented ·

Think we need to slow down a bit. If you go to 20 300W panels, that is 6000 or more (depending on the temperature),Watts of power. Now you are exceeding the amperage limitation of your controller. Not on the PV side but on the battery side.


For this large of a system I strongly recommend that you consult a Victron Certified Installer to assist you in designing and installing the complete system.

There are life safety issues, not to mention the financial impact if it is done incorrectly.

Pat

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JohnC avatar image JohnC ♦ Pat Davitt commented ·

The 250/100 will simply limit itself to 100A into 48V nominal. In practice that may reach (say) 58V, so 5800W. 20x of those panels would rarely reach that, and would just 'clip' if they did.

We've discussed max string Voc, but the other thing to watch for is total string Isc. In this case, 5x 8.93 = 45A (My bad, edited to 4x 8.93 = 36A). Well under the 70A spec of that mppt.

'Overclocking' pv W is often standard procedure, and quite safe providing those other constraints are respected.

Not saying a Victron installer shouldn't be consulted/commissioned, but all should be sweet.


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Elimac avatar image Elimac commented ·

Yes, strings of 5 panels. Voltage is within acceptable levels. 15 panels divided by 3 strings would match the controller well, the 4th string may be left out, unless you don't have much sun for lengthy periods of the year.

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chyk101 avatar image chyk101 Elimac commented ·

Thank you

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