How to generate a PVLIB fit_desoto module with only cells_in_series as an input parameter, but which may have 2 in parallel as well?

While using fit_desoto

Vals=fit_sdm_desoto(v_mp, i_mp, v_oc, i_sc, alpha_sc,beta_voc,
                   cells_in_series, EgRef=1.121, dEgdT=-0.0002677,
                   temp_ref=25, irrad_ref=1000)

we typically enter the datasheet values.

However, here, only cells_in_series is an input, many other types of panels, have 60 cells in series with 2 in parallel, bringing the total to 120 cells (eg this one)

What is the correct way then to enter the information? Should we be adjusting the i_mp, i_sc etc or treating the models differently or entering 120 rather than 60. Based on the above datasheeet i would have entered

i_sc, v_oc, i_mp, v_mp, alpha_sc, beta_voc, cells_in_series, gamma_pmp

12.14,40.8, 11.54, 33.8, 0.004856, -0.102, 60, -0.34

What is the correct way to deal with cells in parallel?


You can pretty much ignore the parallel cells for the single-diode models. Two cells that are internally connected in parallel just provide double the current of one. The parameter cells_in_series should therefore have the value 60 for this module and you do not need to change any module current or voltage values.

If ever in doubt about the number of cells (in a c-Si module), just divide Vmpp by 0.5 and you should get something close.

However, you will need to modify your temperature coefficient values. The spec sheet lists %/K and pvlib expects A/K and V/K.