@PotatoBattery You have probably already found the solution for your issue, but for the sake of variety, here is my take on the matter. [image: upload-41343723-da07-492a-ad92-a2c3f45a7bfa.jpg] The battery is a generic lithium phone battery, 2300mAh in this case. The solar cell is a 5,5V, 30mAh one. It is enclosed in resin. The battery charger is a 1A lithium charger with battery protection. I've replaced the programming resistor with a 10k, to better suit the solar cell output current capabilities. The battery gets 15mA, on a sunny day. All the components are from eBay. And you can buy the Arudino board here, on mysensors.org. [image: upload-0709f7e6-73c0-4276-bde9-64bc76a97947.jpg] Everything fit perfectly. [image: upload-87599f77-07ab-4173-9a25-8463fd73875a.jpg]