In my experience on the average cloudy day you will be lucky to get 10% of what the panel is rated. More likely you will get 5%.
I have a panel rated at 50 watts. In my location I have seen it produce up to 42 watts. On the average cloudy day, I will see about 5 watts during peak hours. On heavily overcast days it produces even less.
Moral of the story, you wont get much from these small foldable panels on cloudy days.
5W in real-world changing weather is about the minimum I would want for practical use in a sustained power outage situation. Just enough to keep a phone charged for entertainment, and an 18650 charged up to get me through the night.
Pretty cool thing to have. I cant wait for mine to arrive. Ill be charging power packs with it and using the power packs to change mobile devices and batteries for flashlights. Im impressed it did over 3amps at 4.3volts on the video
BW-L3 managed to clock 1A per channel easily with partial clouds about to sea level height. I couldn't plug in two USB testers simultaneously as there was not enough spacing in between the ports. That was why i had to reschedule for another day where weather is more ideal.