this might be the same thing Fitz already designed for the disaster radio system, to manage solar charge and battery stuff, or maybe its design or production could improve our situation, i don't know: "Solar Power Manager 5V is a small power solar power management module designed for 5V solar panel. It features as MPPT (Maximum Power Point Tracking) function, maximizing the efficiency of the solar panel, suitable for various solar power projects." https://www.dfrobot.com/product-1712.html