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zeroco2 avatar image
zeroco2 asked

Oversizing the PV part versus the inverter

Hi there,

Due to a non optimal roof orientation (& slope), I need to oversize the PV part (2 strings of 5 Trina panels 650 W each, connected to 250/60 MPPT modules) versus the inverter (Victron Energy MultiPlus-II 48/5000/70-50): is it a problem if I connect a PV part (modules + MPPT) of 6,5 kW to an inverter of 4 kW ? In june, july & august, the PV part should hardly output over 4 kW (probably reaching 4.6 kW max). Or should I take a MultiPlus-II 48/8000 which is twice the price ?

Best,

Jean-François

MultiPlus Quattro Inverter Charger
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2 Answers
Alexandra avatar image
Alexandra answered ·

@ZeroCO2

No it is not a problem for the inverter. The 1:1 ratio on PV refers to AC PV.

We often size DC PV 3x (or more depending on how offgrid the person is) the power of the inverter. What really matters is can the battery bank take the amps?

FYI one 250v/60A mppt only outputs 60A so at 48v that is 2880W. Or are you getting 2 mppts?

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zeroco2 avatar image zeroco2 commented ·

@Alexandra

Thank you for the answer.

Yes, I will get two MPPTs (one for each string), and given the max. expected PV output (< 5 kW according to PVsol), at 48 V, the battery charging current should remain under 100 A (but close to it in summer), which is the max allowed for the Pylontech Force-L2 10.65 kWh (peak 105 A during 15 s). Should the charging current exceeds this 100 A limit, the Pylontech BMS would protect the battery modules ? I'll try to find tech data on this.

Take care

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Alexandra avatar image Alexandra ♦ zeroco2 commented ·
@ZeroCO2

The Pylontec if set up as outlined in the Victron guide, you should not have issues.

Make sure you meet the minimum battery sizing recommendations.

And check your mppt set up with the calculations from victron. The 250V is a hard limit at low temps. Meaning smoke comes out when over voltaged

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klim8skeptic avatar image
klim8skeptic answered ·

650 watt panels, wow.

You are going to need giants to install them?

4 rows of rails to hold them down??

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zeroco2 avatar image zeroco2 commented ·

@klim8skeptic a few dwarfs will do it :o) the 650 W panel dimensions are 2384 mm x 1303 mm, I will mount them with 3 rails

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klim8skeptic avatar image klim8skeptic ♦ zeroco2 commented ·
@ZeroCO2 Panel envy ;)
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