I really love all your projects at https://www.tindie.com/stores/bobricius/
but what I really need is PCB to read a single solar cell 0.5V 8A input and
give useful 5V , 12V voltage as output
or serve as a Li-Ion cell charger

Not sure if any of your other Joule thief projects could be redesigned to accept 0.5V as input

https://www.tindie.com/products/bobricius/joule-thief-smd-dcdc-white-led/

operating voltage: 0.9V-1.5V
output current adjusted to: 5mA
input current : 15mA

https://www.tindie.com/products/bobricius/75mv-joule-thief-powered-with-body-heat/

So the question is how to turn 0.5V  8A (4W) input into  5V 0.8A output  .

greetings,

I know only one chip http://www.analog.com/en/products/power-management/energy-harvesting/ltc3105.html#product-overview

0.5V is very low for everything

thank you
400mA Step-Up DC/DC only
in theory I can boost voltage with lens concentrated cell
but still too much energy wasted
China manufacturers can cut 8A 0.5V single solar cell into smaller parts connected in serial to boost output voltage
Unfortunately, either cutting or soldering is heavy
I have tried to order pre-soldered solar cell strings from solar company to get it laminated.
Unfortunately, growing solar modul in size, laminating is more expensive and complicated and there is a higher risk of getting the job broken easily.
So I would love a single solar cell DC DC step up inverter one day

You'll need to think beyond Joule thief as it isn't practical for that kind of wattage nor that voltage.

I am working on my project, but don't think it would deliver 4W.  I am guessing 0.5W (or may be a bit higher) might be a realistic number.  I don't have the answer until I try.  0.5V is not an easy voltage to work with as most common parts do not work on that natively.

https://hackaday.io/project/158839-boost-converter-for-low-voltage

thank you

what about rechargeable coin battery, coming with solar keyboard ?

It is ML2032

exactly, you offer charger for ML2032 coin cells

I agree with Marian (above).  Resistance of coin cells is something integral to several circuits.

Also, the Tindie price is quite high for such a simple board.

Great idea!

I think you just invented a pretty interesting connector in there...

lollipop :D

Now make the output voltage adjustable and add an adjustable series resistance, and this would be really helpful in development.