When one of the four squares is covered, the delivered current drops to 0 mA. The manufacturer probably saved four bypass diodes, cutting a couple of CZK in production costs. In direct sunlight it gives about 300 mA/5 V. Any covering “across a square” (e.g., with a backpack zip tie) reduces the current by an order of magnitude (to a meager ~30 mA). Cannot be used as a canopy where one side charges in the morning and the other in the evening. When charging a PD power bank via a data cable, the panel’s converter first “trips on overcurrent,” but after a few seconds they “settle” and charging works the same as with a two‑wire charging cable. Panel rating: poor price/performance ratio.