I live in a place where the temperatures can range from -20°C to +40°C in different seasons. I need to power a small micro-controller that uses very low energy with a solar panel and a battery. Which kind of battery is more suitable for this work? It must have the following characteristics:
- It should resist to temperatures from -20°C to +40°C.
- It's not important to store a lot of energy, 500mAh will be fine.
- It should output at least 5V. If less I will have to put two or more batteries in series.
- It should not require maintenance.
- It should live for a decade or more.
- It will be pretty always charged since the solar panel will be directly connected to it (or maybe, via software, I can make some cycles of charge/discharge).
which battery do you recommend?
Explanation of the project
I'm following an IoT course at my university, and I'm free to propose a custom project that will be part of the final exam. I thought about a series of small boxes that will allow us to check if a parking slot is free or not. The box will be build with my 3D-printer and it will include: a small solar panel with a maximum power of 9V * 50mA in the best case (size 60x80mm); a battery of at least 500mA that will be charged by the solar panel; a proximity/distance waterproof sensor that will check if a car is parked on the slot; a MCU with WiFi to send data to an other sensor or to a master with a raspberry pi. I will take inspiration from internet for the routing of packets through this "network" of boxes. Not all boxes will be directly connected to the master box.... We are already experimenting plastics to build a box strong enough to resist to the wheels of a car. The solar panel will be protected with a non-scratchable piece of plexiglass. Sensors will be cleaned from leaves and earth by rain, by road-cleaners and by the wind. Our roads are very clean. The major problem we are facing is to choose the best battery to be used in this "extreme" application. In winter, at night, the temperatures can drop up to -20°C while in summer, during sunny days, it's possible to reach +40°C. Finally, we will develop an App that will give you the nearest free parking slot.