High Efficiency: Built with 12W SunPower polysilicon solar panels, its maximum solar conversion efficiency is up to 22%. Great for providing power to charge two devices simultaneously while converting extra sunlight into energy and storing in the built-in battery. 10000 mAh Battery Capacity: Internal 10000 mAh lithium polymer battery, rechargeable via solar panels, is ideal for charging your smartphones, tablets, GPS or other USB-enabled devices. With 4 LED lights to indicate battery levels. Dual USB Ports: Automatically detect your device and deliver the fastest possible charging speed up to 2.1 amps per port or 2.1 amps overall. During solar charging, it charges connected devices first. Foldable & Portable: Compact size and foldable design enable easy storage and carrying. Well-placed eyelets allow easy attachment to backpacks, trees, or tents. Safe & Reliable: Built-in over charging, over discharging, over current, and short circuit protection keep you and your devices safe.