One thing about solar is that existing commercial solar generators are <i>really good</i>. They're cheap and reliable and packed with features.<p>Plus, they're self contained and protected and have built in CYA. Not that it's all that hard to do this stuff safely, but off the shelf has a certain peace of mind.<p>LiFePo4 ones are meant to last 2000 cycles. They can charge via USB-C as well as from solar, and they have inverters as well.<p>Obviously, anything lithium isn't environmentally perfect, but I would imagine it will all be recyclable eventually, if it fails before then, just keep it and wait, it's small.<p>There's a bit of environmental issue with the non-replacable built in battery, though, but one could probably get around that with some hacking if they really want to replace it.<p>Portable folding solar panels are also insanely cheap for what they offer, sometimes they're less that $1/W, and they often have USB-C output to direct charge devices, in addition to 2.1mm.<p>Lithium does not like to be charged below freezing, which is another advantage for having everything compact and portable so you can bring it in.<p>I think that if I were going to build a fixed and permanently installed small solar setup, I would just want a panel with an outlet inside for a solar generator.<p>I'd add a switch, fuses, a reverse blocking diode, and a decent quick connector of some sort.<p>I might also add a voltage meter, and perhaps a USB charger, or even cigarette lighter outlet(with a 2 or 3A fuse, at most, definitely wouldn't trust a cigarette plug with 10A)<p>Most likely, I'd use Anderson PowerPoles for the main output, they seem to have a semi-standard for solar power (<a href="https://oh8stn.org/blog/2020/07/11/when-standards-get-in-the-way-of-common-sense-anderson-powerpoles/" rel="nofollow">https://oh8stn.org/blog/2020/07/11/when-standards-get-in-the...</a>)<p>Then, I would make a pigtail (With it's own inline fuse, in case the panel ever gets swapped with a much bigger one!) going from Anderson to 2.1mm, and plug that into the off the shelf solar generator.<p>I'd probably make a shelf for it, and position stuff such that the cable wouldn't easily bump into some rusty bucket of screws and short out.<p>In all the research I've done, aside from using batteries with built-in heating, I've never seen any easy way to recharge lithium in very cold temperatures.<p>The closest I've seen to a solution would be insulating the battery, and using two temperature switches, one to cut charging below zero, and one to turn on heating to warm it above zero using the solar energy. No idea how practical that would be, though.<p>Or, just using ultra capacitors, as I'll probably do if I get around to building a Meshtastic solar repeater.