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Danny Evans avatar image
Danny Evans asked

EasySolar-II 5kVA MPPT 250/100 GX Max solar input voltage limit

I'd like to know if I can actually connect 250v (Voc) to the EasySolar-II 5kVA MPPT 250/100 GX.
I have 18 x 370w panels with a Voc of 41.28v. I'd like to connect these in 3 strings of 6 panels. That equates to a (Voc) of 247.68v per string.
The data sheet says I can connect up to 250v (Voc) but the online calculator suggests that the voltage is just too high. https://www.victronenergy.com/mppt-calculator
I was unaware of the calculator when purchasing the panels and thought the data sheet specs would tell me all I needed to know.
The panels will never see sun and be below zero degrees C where I live. It is likely they will never see full irradiance at lower than 10 degrees C. According to the calculator that doesn't make a big enough difference.
Is there any leeway? Can I use the panels as intended or will I have to reconfigure them or use others to make use of the easy solar system?

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JohnC avatar image
JohnC answered ·

Hi @Danny Evans

Don't do it, it's not worth the risk. You'll have a nice system there, and to have that self-inflicted risk of failure hanging over your head wouldn't be worth it for me.

I've *never* seen Victron suggest that there's any sort of leeway. It's a hard limit, a warranty killer if you exceed it. Your panels may come with +/- specs, but not the mppt.

You mention "they will never see full irradiance at lower than 10 degrees C". Trouble is, panels don't need full irradiance to reach full V. They can easily reach spec Voc with less load and irradiance. And that will happen.

Without changing the panel numbers (you could), I'd wire the 18 as 3S6P. Amps will rise of course, so you'd need to look closely at the number of wire pairs/size. But you may even see better performance if you have selective shading.


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Danny Evans avatar image Danny Evans commented ·

Thank you, I very much appreciate your input. It isn't worth the risk to me either I just wasn't sure it was a risk.


I guess I am just a bit miffed to find out after the planning and purchasing that I can't do as intended. The datasheet didn't give any indications that would have prevented the planning as I did.


I can't easily change the panel numbers without wasting panels. I had considered the 3S6P config but I'm not sure I can wire it up effectively. Can I ask how you would wire 6 parallel connections to the unit? I can run 6 cable pairs from each series array but I'm not sure how to then join them in parallel physically to have a single pair of wires entering the easysolar unit.

The other consideration with the 3S6P config is the "Maximum PV Array short circuit current" which the manual states is 35A. By my calculations the 3S6P config would lead to a total of ~68A with my panels (11.24 Isc per panel)


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ejrossouw avatar image ejrossouw Danny Evans commented ·

You can do it with a string combiner similar to https://uk.eco-worthy.com/products/6-string-pv-combiner-box-with-lightning-arrester-10a-rated-current-fuse-circuit-breakers-for-on-off-grid-solar-system and then have one connection from it to the EasySolar

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Danny Evans avatar image Danny Evans ejrossouw commented ·
That looks like the ideal solution. Thanks for pointing it out. I found a local (I am in Australia) supplier with a similar 6 input combiner with 15amp fuses. Looks ideal for my gear.
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kevgermany avatar image kevgermany ♦♦ Danny Evans commented ·
Isc must not be exceeded.

Also with multiple strings you will need to put fuses in each string. There are online guides to this.

I think.... Fusing correctly gets you around the Isc limitations. Hopefully one of the others will chime in.

On your frustrations, fully agree, but this is a high voltage system that should have expert professional help and installation.


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Danny Evans avatar image Danny Evans kevgermany ♦♦ commented ·

Thanks for your help.

The confusion only increases the closer I get to the end goal. So the manual states 35A as the maximum PV array short circuit current but the calculator seems to suggest the 3S6P config is suited to my easysolar unit and states (Current numbers written in yellow if that means anything):

PV max. current @ MPP min. temp. 100 A
* Power limiting @ low temp.
PV max. current @ MPP max. temp. 100 A
** Power limiting @ high temp.


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JohnC avatar image JohnC ♦ Danny Evans commented ·

@Danny Evans

Don't get miffed, get excited. A great system is still there to be had. Panel stringing always comes with compromises. Always..

I don't know your setup, distances, etc. Nor your panel Isc (check that, the mppt is rated 70A, but there may be leeway there).

I'd probably run 3x 6mm2 solar wire pairs to the mppt. Wired at the panel end with 2-into-1 MC4 adaptors to get the parallel links. This is pretty easy stuff, but you'll find you'll need to map it out to get the right bits, male to female, etc.

At the mppt end I'd run the 3 solar pairs through 3 20A double pole dc breakers, then on by whatever you choose to the Easy.

If it makes you feel better, I also have an Easysolar, a >7yo one with a 150/100 mppt. That's how mine's wired. Works great. Love my Victron kit..

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Danny Evans avatar image Danny Evans JohnC ♦ commented ·

I'm going between miffed, excited, depressed and elated on a rotational basis ;)

I very much appreciate your help.

I'm pretty used to wiring MC4 connectors and using y cables or branch connectors. Someone else suggested a combiner box which I like the look of.

The current limit is now my only real concern. If you have time and energy I'd appreciate your opinion on my Victron MPPT calculator results:
https://mppt.victronenergy.com#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JohnC avatar image JohnC ♦ Danny Evans commented ·

@Danny Evans

All looks good to me. The 11.24 Isc is up there as expected, but 6x is still below the 70A. Which isn't actually shown in the Easysolar data sheet, but this is essentially the same device..https://www.victronenergy.com/upload/documents/Datasheet-BlueSolar-charge-controller-MPPT-250-70,-150-100-&-250-100-VE.Can-EN.pdf.

As long as you're happy with 3S6P configuration, I see no downside to it in practice. Maybe better shade tolerance and a lower V for safety could be considered pros.

How you wire it is personal preference really. I prefer my breakers near the Easy cos I'm not much into climbing stairs.. :)

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Danny Evans avatar image Danny Evans JohnC ♦ commented ·
Thanks again. I have breakers at the Easysolar end but I don't mind the idea of the combiner box up near the panels. More fusing cant really hurt and I like the idea of one cable pair coming down from the roof.


Your comments really helped.


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nickdb avatar image
nickdb answered ·

It is a MPPT 250/100, so you will find everything you need on its datasheet.

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Danny Evans avatar image Danny Evans commented ·

The Victron MPPT calculator shows the unit I have is not compatible with the panels I have as I planned to use them. However as I stated in the question the Voc is below what is stated in the data sheet (or the product name for that matter).

Here is a link to the data sheet. It makes no mention of the variables accounted for in the calculator.
https://www.victronenergy.com.au/upload/documents/Datasheet-EasySolar-II-24V-48V-3kVA-48V-5kVA-MPPT-250-70-100-GX-EN.pdf

The manual for the EasySolar-II 5kVA MPPT 250/100 GX states: "We recommend to use the MPPT Sizing Calculator available on our website"

It further states:
• The solar charge controller will operate only if the PV voltage exceeds battery voltage (Vbat).
• PV voltage must exceed Vbat + 5V for the controller to start. Thereafter minimum PV voltage is Vbat + 1V.
• Maximum PV Array open circuit voltage is 250V.
• Maximum PV Array short circuit current is 35A.
For example:
• Minimum number of cells in series: 144 (4x 12V panel or 2x 24V panel in series).
• Maximum: 360 cells (10x 12V or 5x 24 panel in series).
Remark: at low temperature, the open circuit voltage of a 360 cell array may exceed 250V, depending on local conditions and cell
specifications. In that case, the number of cells in series must be reduced

I'm finding it all pretty confusing.



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