Battery Mountable - The solar panel has four 18650 battery slots, with standard 18650 battery dimensions for easy battery installation. MCU Charging Management - A low-power MCU core processor provides precise management of the entire solar panel's charging and discharging, ensuring optimal operation. Monocrystalline Silicon Solar Panel Battery - The solar cells use monocrystalline silicon, achieving a conversion efficiency of up to 25%, significantly improving the efficiency of converting sunlight into electrical energy. Constant Current Voltage Regulator Circuit Board - Built-in PCBA, which outputs a stable 5V voltage from the battery through a constant current circuit to power the device and maintain optimal operating conditions. Note: LoRa module and battery not included; please purchase separately. This kit supports Heltec LoRa32 V3, RAK4631 modules, and some LEGO modules. Please note this when purchasing. Solar Panel Power: 8W Output Voltage: 5V Color: Black Material: ABS Package Contents: 1*Solar Panels(without 4*18650 batteries)