My wish list for building this relay, was as follows.
Able to get sufficient sunlight to run the relay year round, even with diminished sunlight in Winter.
Battery insulator and/or heating circuit to keep the batteries above freezing to avoid temporary or permanent loss of capacity.
A casing, water and dust proof.
Download this link for an excel spreadsheet of below with hyperlinks, pricing, instructions, images and diagrams.
Link with diagrams, excel spreadsheet with pricing, instructions, photos etc
Never ever, power up radios without an antenna connected, if fries the circuit.
Shopping list - Solar Powered Relay:
Solar Panel - Dokio 12V 20W Small Solar Panel China 18V Solar Charge Polycrystalline Silicon Solar panel DSP 20M/20P|18v solar|polycrystalline siliconsilicon panel - AliExpress
LiPeO4 Batteries - 2pcs/LOT Soshine 3.2V 18650 LifePO4 Battery Cell 1800mAH Protected Positive nipple for Led Torch Headlamp Bicycle Light|soshine 18650|cell 18650soshine 18650 lifepo4 - AliExpress
Cable from Solar Panel to Charge Controller (1m) - Square 0.5mm Black Ultra Soft Sheath Wire 2 3 4 Core Silicone Rubber Cable Insulated Flexible Copper High Temperature Power Line|Wires & Cables| - AliExpress
18650 x Parallel battery holder - Holder Box Case 2x 18650 3.7V Parallel Corded Akku Battery für Arduino Raspberry | eBay
Solar MPPT Charger Controller - Buy with optional Thermistor & 3.07A Version - https://www.tindie.com/products/silicognition/lifepo4weredsolar1/
Antenna - SDD21-868-SMA - Ideetron
Radio - LILYGO® TTGO Meshtastic T Beam V1.1 ESP32 433/868/915/923Mhz WiFi Bluetooth ESP32 GPS NEO 6M SMA 18650 Battery Holder With OLED|Circuits| - AliExpress
Electrical Waterproof box with waterproof plugs to allow aerial to be mounted out through the casing and same for wiring for solar panel - https://ie.farnell.com/abb/1sl0856a00/junction-box-ip65-thermoplastic/dp/2529544 (Best to buy from local electrical store, buy last when you have your antenna and solar cable to get the right sized plugs)
Resistor to be used as battery heater - RESISTOR 150 Ohm 3W Metal Film Resistor (LOT OF 10) | eBay
(Hammond Box 1591xxCBTU) Casing to act as insulation box for batteries and mppt charge controller - Genuine Hammond Blue & Black ABS Plastic Enclosure Project Box Case | eBay