# Module Parasitic Resistances

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Hello PVsyst Users,

I have obtained parasitic resistances from the module manufacturer in order to obtain a more accurate simulation with regards low irradiance module performance. However, the value given for series resistance is approximately double that of the Rseries max (Rs = 0.72 ohm and Rsh = 260 ohm). Is there any way to modify the parasitic resistances in PVsyst according to values provided by manufacturers? I understand some manufacturers provide specific parasitic resistance values for use in PVsyst as they believe the values calculated in the PVsyst model are not representative of the real values. These values significantly affect module performance at low irradiance, which can make a large difference to the overall PR

Thanks,

Rapha

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What you call "Parasitic resistance" is named "Series resistance" in PVsyst.

Please observe that the measured Rserie proposed by the manufacturer is not the Rserie as defined in the one-diode model. See ou FAQ I can't specify my measured Rserie.

NB: With version 5, the best way of setting a reliable value to the Rserie of the One-diode model, is to try to reproduce the low-light performances if these are provided by the manufacturer.

You can analyse this in PVsyst, using the graph "Efficiency as function of Irradiance", and proceed by trys and errors.

There is now a tool for performing directly this adjustment in the version 6.

Please also see our FAQ What explaind differences of yield between different modules ?

Thanks Andre.
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• 3 years later...

Hi Andre,

I tried to calculate Rser and Rsh by reverse feeding the values in this equation, but resultant values were not matched with PVsyst.

Can we calculate by this way? is any other equations there to find Rser and Rsh?

I = Iph - Io [ exp (q · (V+I·Rs) / ( Ncs·Gamma·k·Tc) ) - 1 ] - (V + I·Rs) / Rsh

Thank you.