Useful links

Bypass diodes

https://www.electronics-tutorials.ws/diode/bypass-diodes.html

Solar cell on Ebay

https://www.ebay.com/sch/i.html?_from=R40&_nkw=solar+cell&_sacat=0&Wattage=Less%2520than%252010%2520W&Type=Solar%2520Cell%252FDIY&rt=nc&_oaa=1&_dcat=41981

Solar energy system

https://www.instructables.com/id/DIY-OFF-GRID-SOLAR-SYSTEM/

Great Scott (another concept, not that good)