This is my solar powered setup. A somewhat old Pixel 6a that fell from a foot and a half (really!?), a 10w Solar setup that was around 20$ on amazon. And an old compost container I have too many of. Ill be giving it a proper 3d printed case when I get a chance (and a host of other changes) but for now this works! Its worth about 40$ in total (the phone is now worth about 21$ on the open market).
Website: https://solar.chrisco.me/
Website was made with a collection of scripts, apache2 (nginx for some reason did not install, errors), and termux. Ill open source the whole setup in a bit. Theres not much to it to be honest.
Hopefully keeping the battery at 80% will help the lifetime of the battery. I may bump it up at some point if it keeps dieing because lack of sunlight. But we shall see.
More info in the link. I couldn't get Piefed to repost from a GotoSocial link.
I'll assume it's cool, but currently hugged to death for me. Just wanted to point out batteries are replaceable even if glued, fixed my GrapheneOS Pixel7 after it killed itself (spicy pillow) charging in heat in a warmer country. iFixit kit + video worked, then got a Chargie which lets you set a temperature above which it will not charge (33C for me, only charges at night in summer). Probably relevant in your case.
With chargie you could keep the battery hovering around 50%