question

rami-alaryan avatar image
rami-alaryan asked

oversizing the 150/35 MPPT CC with 1300W-Solar installation

Dear Victron community,

greetings,

I am seeking your kind guidance/advice on the below installation setup if it should be ok?

1- I have three solar panels connected in series (420W, VOC=42v, Isc=14Amps),

2- I will be charging two (parallel connected) (12V / 200AH) batteries ... resulting in a total (12V-400AH) ... battery bank, the batteries are LeadAcid Flooded Tubular.

3- Due to my apartment/location limitations, I can only point my panels towards the west only so I need to take utmost advantage of the indirect/scattered sunlight as much as possible.

4- With the above in mind and considering that my budget is limited, I thought of solar-oversizing my MPPT charge controller, thus I am planning on using a (Victron 150/35 MPPT) with the (1260W) solar pannels, knowing that I can only effectively get a maximum of (35*12= 420 W) at any given time ....... but still I was hoping that the solar-oversizing will kind of compensate for the "improper solar panel direction" and would also give me some boost/advantage in the cloudy days.

yet I am still worried would this setup technically cause any damage to the MPPT charge controller due to the solar-Watt-oversizing?

Also, I am concerned that if I have used a larger MPPT controller "let's say 60 or 70 Amps" this would cause a violation of the max allowable charging current for the battery bank capacity, in this case, 10% of the total capacity (10% * 400AH = 40 Amps ) ??

Thank you in advance for your feedback and advice on this.

With kindest regards

MPPT Controllers
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2 Answers
wkirby avatar image
wkirby answered ·

Yes, you can over size the array. The MPPT will only take as much power as it can take from the array with a limit of 35A to the battery as you know.

Of course, make sure the array Voltage is below 150V and that the PV array short circuit current is below 40A.

Probably a good idea to limit the charge current to the battery according to the battery manufacturer specifications.
You could use a larger size MPPT charge controller if your budget allows. It is possible to limit the charge current also in the VictronConect app. This is only really useful if you plan to expand your system in the future.

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rami-alaryan avatar image
rami-alaryan answered ·

Thank you dear Wkirby for the advice, appreciated!

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nickdb avatar image nickdb ♦♦ commented ·
It will pay to get a professional to do all the expected PV maths for you, over-sizing only helps if you can use it. If your orientation is poor, or there is shading etc, you could just pour money down the drain for little benefit.


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rami-alaryan avatar image rami-alaryan nickdb ♦♦ commented ·
Thank you dear Nickdb for the advice,

This setup was kind of chosen because I had a 12V/1300 VA inverter already available and I needed to take advantage of it as part of the small backup system.

and yes indeed, I might take your useful advice starting with only one or two 420W solar panels in series and based on the observed-results move forward with the third one.

With my kindest regards

Rami

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