This work is mainly concerned with the improved photoelectrothermal (IPET) modeling of an extra-high current (EHC)and extra-high luminous flux (up to 60 klm) solid-state light source based on a chip-on-board (COB) light-emitting diode (LED).The studied COB technology presents the particular challenge of extremely small thermal resistances, with extra-high currentlevels through the lamp (up to 12 A). Considering the unique thermal characteristics of such devices, an improved PET modelingand its respective experimental methodology are detailed. Accurate techniques are also proposed to estimate the device junction temperature.The studied method is very suitable to represent EHC COB devices, since it includes the main thermal parameters variation into a novel model,optimizing the flux prediction for this technology. In this context, the static flux and efficacy are analyzed by means of experimental testsand theoretical model, where the improvement of the employed method is highlighted.