Low power solar. What is the "best" way?

If you choose to go with the small one (see previous image in post #5), then there's enough space for a Nano or a Pro Mini. Get the 3v3 version so you can run directly from the battery.

It'll probably take one of the Adafruit Feather boards with a built-in radio module.

You should look for a board that has a built-in radio module as there's just enough room for 1 daughter board or a small collection of hard wired sensor boards.

Evening.

Yeah was hoping to see how it works with a 6V smaller panel (that one isn't 6V sadly...was only 2V!).
I have some 6V 80mm dia ones on the way which is larger than I would have liked.

Also I've found some square ones at 5.5V which may be enough and are about 50x50mm which is more acceptable.

I need to test it all together really before making the panel any smaller as I guess that is the main limitation I have.

I may need the 80mm anyway as I was hoping an nrf24, ATTiny84a and say a AM2302 so I am somewhat limited by the size of the AM2302 anyway. I guess I may be able to have the AM2302 sit sort of underneath the NRF module thing (which sits proud of the board via the 6 pin header.

I am quite interested in the ATtiny84a as at 4MHz it will run down to 1.8V, but I guess this isn't much use anyway as say the AM2302 says a 3.3V minimum supply...which kinda defeats the objective.

Is the only real way to have this work is maybe to have say a 9V panel and a ~8-8.3V supercap. Just seems wasteful as I guess about 50% of the energy will be just wasted by the 3.3V regulator but overall it would work for longer (albeit with a much larger supercap)?

Thank you :).