I have tested solar node’s with both ESP32 and RAK5005 with NRF52.
My experience is that when an unprotected li-ion cel was totally discharged the node did not come back after the solar panel charged the battery again.
This may be normal behaviour when charging and the cel-voltage slowly rises, the ESP or NRF will not start normally and comes in an undefined state. Because the processors auto-reset function cannot handle this slowly rising voltage.
At least that is my experience with normal unprotected li-ion 18650 cells.
I did not test this with a protected cel.
Does anyone have tested a solar node with protected cells ?
I wonder after a shutoff at 2.5 V due to darkness/bad weather etc , when the sun shines again and the protected cell ‘suddenly’ comes to live again, would this be good enough to let the solar node startup normally?
I guess it may depend on the kind of protection circuit and the brand of the battery. I do not own any protected li-ion cell so cannot test this case.