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christiaan avatar image
christiaan asked

Smart Solar Charge Controller Maximum Permitted PV input

Good Day All.


I would like to know, if using a Smart Controller 250/100 It states the following in the datasheet:

1605098885336.png

Taking a look at the "Nominal PV Power, 48V" it states that 5800W should be used. I am using 425W panels and have made 5 strings consisting of 5 series panels each , not exceeding the Voltage rating and not coming close to the input current limitation of 70A(Please confirm I understand the input current correctly or not?).


Adding these I get 425*5=2125W/String thus 2125W*5=10 625W input power into my charge controller, now I know it states a "Nominal PV Power" but my panels configuration does not exceed the 250V or 70A input characteristics. Does this mean that the charge controller will only deliver the rated charging current 70Ax48V=4800W (in ideal conditions)?


My last question is, if I over panel more than 20%(Compensate for shading etc) will that charge controller still only output the rated charge current, will I waste the additional over panels then?

Greetings

Christiaan

MPPT Controllerscharger
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4 Answers
JohnC avatar image
JohnC answered ·

Hi @Christiaan

Let's say your panels are rated 10.0 Isc. Any number in a string will still give 10A, so the 70A limit covers 7 strings.

The 100A output limit at a nominal charge V of 58.0V = 5800W. That doesn't happen much in practice, but yes it would be fine to 'overclock' your panels as much as you want, providing the Isc isn't exceeded.

But the panel Voc limit is even more important, and not so clear-cut. You say 5x in a string, but you MUST allow for a hefty increase in Voc when the Temp is low, and that's why the panel maker will specify Temp Coefficients. And don't think that at dawn when it's 0 degC but there's so little sun that it won't reach the corrected Voc, because you'd be wrong.

Please run your panel data through this calculator before you decide on a 5x string. You may not make it..

https://mppt.victronenergy.com/


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JohnC avatar image
JohnC answered ·

@Christiaan

Yes, you'll lose the energy beyond 100A (I won't say 5800W). But if you're not exporting to grid then as an issue it may not exist at all. Offgridders (like me) are usually happy to see battery Absorb reached by (say) 11am, and the rest of the day's potential go unharvested. The battery is the priority, nothing else matters.. :)

Where that 'overclocking' is welcome is on the foul days, and I've seen my solar output reduce to as low as a 20th of what I know it can do over a full day.

Take care reading specsheets, they can consume you. They don't explain that a day's solar potential is in the form of a bellcurve, with maybe a little 'clipped' off the top, or that winter devastates their panel's potential.

There's other stuff too, but I'm sure you're aware of much of it. If offgrid, this is fun to play with: https://www.victronenergy.com/markets/off-grid

And pleeease don't spend anything until you've worked out what you really want. And run it past us again.. :)


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christiaan avatar image
christiaan answered ·

Hi @JohnC

Thank you for the answer, I will run my panels through Victron's calculator as well.

A follow up question on the charge controllers on what was mentioned above:

Lets say I am using 4panels/string and there are 5 strings. +-200V @ 10A each.

The power capacity of the panels is 425W*4*5= 8 500W in total which will be connected to the charge controller. Will I waste the additional 8 500W - 5 800W = 2700W?

Would it be better to use the charge controller only with the "Nominal PV power - 5800W of panels" and then If I have remaining panels use another charge controller? The size of the charge controllers can be chosen so they balance out.



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christiaan avatar image
christiaan answered ·

Hi @JohnC


Thank you for the well elaborated explanation, I will keep it in mind.

I will be sure to go and checkout that link and study up a bit more before buying :).

Stay well.


Kind regards

Christiaan

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