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martin-modr asked

MPPT 150/100 - overload?

Hello everyone.

Please help with my photovoltaic power plant.
I have a complete solution from Victron Energy. Look at the schema: schema.png

I'm afraid the company didn't do everything right.

1) MPPT 150/100
Two MPPT 150/100 are used. 9 pieces of PV panels are connected for MPPT. 3 pieces in series and these three series in parallel. See schema above.
mppt.pngI did the calculation at https://www.victronenergy.com/mppt-calculator. For 3x3 panels it comes out at the lowest temperature U=162.9 V < 150.0 V. Is it ok? Can the MPPT disconnect automatically? Is there any danger to MPPT?

2) The tenth panel
https://www.geosun.cz/media/files/filesgroup/ibex_132mhc_eiger_495_500_1.pdf
There are 3x3 panels in one string, 3 pieces in series and these series are three in parallel. The tenth panel (red) is connected in parallel to another panel. See schema above. Is this wiring OK? Will the total output be 5 kWp or only 4.5 kWp?

3) Wires Wires with a cross-section of 6 mm2 are used. The fuse is only before the MPPT together for 10 panels. It's alright?

The company says everything is fine. I am very worried. Thanks for the help!

Martin

MPPT Controllers
mppt.png (127.9 KiB)
schema.png (15.3 KiB)
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seb71 avatar image seb71 commented ·

1) The string Voc voltage is too high for a 150/xx MPPT. There is no protection for this, so the MPPTs will be damaged.

2) The 10th panel has no place there.

3) When there are more than 2 strings in parallel, each string should be fused (with gPV type fuses - possibly 15A - but the value must be calculated).

Up to these string fuses, 6mm2 is OK.

From the connection/join point of the string wires to the MPPT, I would use larger wires - depending of how many strings in parallel (with another - larger - gPV fuse and a disconnector switch - so that you can disconnect the PV array from the MPPT).

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JohnC answered ·

Well spotted @Martin Modr. One other little thing.. the 11.17 Imp you've used tn the calculator doesn't gel. With the same Vmp, that would mean ~450W panels. I hope you haven't been dudded there too.

Probably the way to fix this is to wire 5x strings of 2 panels to each mppt (2S5P). Should scrape in to the 70A input limit of the mppt, but might need larger/more wires and fusing. Should still work ok with 48V batteries under varied conditions.


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seb71 avatar image seb71 commented ·

Right. In the pdf the STC values for the 500W PV panel are:
Voc = 48.83V (same as the value used in the calculator)

Isc = 13.20A (in the calculator the value used is 12.31A)

Vmpp = 40.62V (same as the value used in the calculator)

Impp = 12.31A (in the calculator the value used is 11.17A)


Maybe he did not bought that system yet. In which case, it's easier to fix (first step is to change the supplier). Either different PV panels (with lower Voc) or a change to 250/xx MPPTs.

5 strings in parallel would not be not my first choice, because of the high current (and unnecessarily low voltage for only 2 PV modules in a string). Unless he already has those components and can't swap them.


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martin-modr answered ·

seb71 says:
3) When there are more than 2 strings in parallel, each string should be fused (with gPV type fuses - possibly 15A - but the value must be calculated).

Is this condition written somewhere?
Any prescription? Can I find it somewhere? Any link?

Thanks.

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