For a while now, I started replacing the dead AA(A) batteries in my sensor nodes with rechargeable NiMH ones. So, since these batteries are rechargeable, I thought, why not trying adding small solar panels for sensor nodes, where light is abundant.
Node 27: outside sensor
Purpose: outside temperature, humidity, light, pressure sensor. Powered by 2 x AAA 500mAh from Ikea. The solar cell is rated 3V, 125mA and is pointing vertically south and costs 0.7 Eur in a pack of 10. The sensor battery normally lasts 6 months with alkaline, due to high frequency readout.
And installed outside with the sensors in the Stevenson screen:
Node 7 – kitchen plants watering
This node replaced my old basil watering system with one where the pump waters 2-4 plants every 1-3 days, depending on the season. It takes care of an Epipremnum aureum and a few herbs. It’s powered by 4xAA NiMh batteries that last 1 to 3 months depending on the season. The added solar panel is rated for 6V, 550mA, 3.5 EUR and hopefully will compensate for some of the battery replacement. The solar panel will stay horizontally on the box and it is just inside the kitchen window. There is little chance it will get sun, but plenty of ambient light.
If the solar panel does not extend the battery life significantly, I will wire this from the mains, it’s the node with the least amount of battery life and annoying to change so often.