Features: 3 independent battery slots, charge up to 3 * 18650 rechargeable batteries independently or simultaneously. (batteries not included.) Dual USB output interfaces, can be backup for 2 digital devices at the same time if battery is inserted. Built-in protective IC, protect your batteries away from overcharge protection, short circuit protection, etc. LCD screen, display batteries status, voltage and current flow. Sliding cover design, batteries can be taken out conveniently. (Battery not included.) Turn off automatically in 10s if no operation, save power.