@NeverDie said in The Harvester: ultimate power supply for the Raybeacon DK: Edit: This guy found another couple of possibilities as to what the E50D chip might be: https://www.electroschematics.com/pfm-module-circuit-surgery/ I have the same board as this guy. I removed the LED and resistor because they are on the input side, so they are almost useless anyway. For a board such as this, with a promised 0.9v startup voltage on the input side and a promised 5v on the output side, they really should have been attached to the output, not the input, to show roughly when it is that the board is producing useable output. At a 20mv "keep alive" input voltage, the input measures 0.5ma using a uCurrent Gold. That means the keep alive energy is 10 microWatts. Offhand, for the application we've been discussing on this thread, I suspect that number is too high to be practically useful, because at only 20mv input we'd be collecting far less than 0.5ma current from a tiny panel. At least now we know.

@Mishka Ah yes, that is true. In this case though I went out of my way to keep the PCB dimensions as small as possible so that someone could have it made at OSH-PARK for super cheap--just $0.30 per board. If I ever figure out how to post a complete set of KiCAD files, then I guess maybe then everyone can modify it to suit their circumstances. Until then, it will be hard to have one's cake and eat it too.

If you wish, you may substitute S-1313 ( http://datasheet.sii-ic.com/en/voltage_regulator/S1313_E.pdf) for the MAX8887EZK27 LDO

What is the max ampere capacity of 3.3V battery it can charge ? Is there any upper limit like 1000mAh or 3300mAh like that ?

Right you are. Live and learn (even at 81), and I even learned a new word -'vias.' Thanks.