remove multiplier on voc for initial interval

Author: cwhanse

pvlib/singlediode.py

@@ -917,7 +917,7 @@ def _lambertw(photocurrent, saturation_current, resistance_series,
     # remove try/except when scipy>=1.15, and golden mean is retired
     try:
         from scipy.optimize.elementwise import find_minimum
-        init = (0., 0.8*v_oc, 1.01*v_oc)
+        init = (0., 0.5*v_oc, v_oc)
         res = find_minimum(_vmp_opt, init,
                            args=(params['photocurrent'],
                                  params['saturation_current'],
@@ -928,7 +928,8 @@ def _lambertw(photocurrent, saturation_current, resistance_series,
         p_mp = -1.*res.f_x
     except ModuleNotFoundError:
         # switch to old golden section method
-        p_mp, v_mp = _golden_sect_DataFrame(params, 0., v_oc * 1.14, _pwr_optfcn)
+        p_mp, v_mp = _golden_sect_DataFrame(params, 0., v_oc * 1.14,
+                                            _pwr_optfcn)
 
     # Find Imp using Lambert W
     i_mp = _lambertw_i_from_v(v_mp, **params)