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mako74 avatar image
mako74 asked

MPPT 100/50 and Victron MPPT Calculator

Hi. I'm trying to figure out solar panels to go with my SmartSolar MPPT 100/50 and I came across a good sized 150W panels that would fit nicely on my vans roof in 2S2P configuration (600Wp total). The Victron MPPT Calculator suggests the MPPT 150/45 for this array. I've already purchased the SmartSolar 100/50 so my question is, is there any reason I couldn't or shouldn't use the 100/50 instead of 150/45 with this array? Is Victron not suggesting the 100/50 because of the Output Current of this array and the 100/50 wouldn't be getting enough current?

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MPPT SmartSolar
1609587270719.png (181.0 KiB)
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lyndon-top-end avatar image lyndon-top-end commented ·
What is the result of feeding the MPPT with panels of different voltages and wattage at the same time?


Thanks for your help.


Regards

Lyndon


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seb71 avatar image
seb71 answered ·

You have to look at VOC (and multiply that with the number of panels in series).

The panels from your link have VOC=22.8V.

Two in series will have VOC=2x22.8=45.6V.

Well under the 100V limit of the SmartSolar 100/50 (including a big safety margin for low temperatures).

You could use even 3 of those panels in series without issues.


For a 12V system, the SmartSolar 100/50 will be used at full power (50A into batteries) when the 600W panel array will produce at its maximum.

In this case, 100/50 is even better than 150/45, so I can't see why the MPPT calculator suggests the 45A charger, instead of the 50A charger. The array VOC is safe for both.


Regarding the PV panels: can't you fit 60 cell panels? Those have better price/power ratio.


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JohnC avatar image
JohnC answered ·

Hi @Mako74

That calculator is just giving you the nearest match in output Amps, and isn't blessed with a retail price database.

There's nothing sinister behind it, and your 100/50 is a great choice.

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seb71 avatar image
seb71 answered ·

For the SmartCharger 100/50 used in a 12V system, the nominal PV array power is 700W.

You can go a little above those 700W to account for cloudy weather, low sun elevation, non-optimal panel angle, etc.

In good solar conditions, you will just not be able to use all the power the PV array would be able to generate.

But in bad conditions the PV array my generate for instance only 1/10 of peak power, so a larger array will be better. Just do not exagerate with the array power over-sizing.

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mako74 avatar image mako74 commented ·

Thanks seb71. I plan to use the van mainly between Lat 65 and Lat 70, where winters are dark and long and as the panels are flat mounted, the sun never really will hits them at the optimum angle even in the summer.

To compensate this I'm installing Orion-Tr 12/12-30 and MultiPlus 12/2000/80 with shorepower input to top up the 2 x 150Ah LiFePO4 bank.

I suppose with the above parameters, the 800W array would be ok with the MPPT 100/50?

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seb71 avatar image seb71 mako74 commented ·

For those conditions, I'll go even for a ~1000Wp array.

I asked if you can fit 60 cell panels. Those have much better prices for same wattage.


Another question: can't you make a 24V system instead (24V battery)? It would use lower currents, so smaller wires (smaller section area). And it would be more versatile.

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mako74 answered ·

Thanks you @JohnC and @seb71 for you quick replies! I understand the VoC not getting anywhere close to frying the MPPT in this case, but I was wondering if there's some sort of optimum range for the input current in where the MPPT likes to operate and hence suggesting the 150/45 version?Pushing the limit even more, what about using this 200W panel and 100/50 for the following array?1609590024713.png


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JohnC avatar image JohnC ♦ commented ·

Those panels would work fine with a 100/50, and give you some relief from poorer solar days. I don't recall ever seeing an 'optimum range' published. And really it's irrelevant, given that solar days follow a bellcurve, and they need to work well over the full range.

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