A 12V 9000mAh battery pack is a compact, rechargeable power source used for small electronics, CCTV cameras, LED lights, routers, and portable DIY projects.
 
Key Specifications & Types
Nominal Voltage: Usually ranges from 11.1V (3-cell Li-ion / 3S)
Capacity: 9000mAh (4Ah), meaning it can supply 9000 milliamps of current for one hour (or lower current for proportionally longer).
Battery Management System (BMS): The pack include a built-in BMS to guard against overcharging, over-discharging, and short circuits.
Lithium-ion (Li-ion): Lightweight, high energy density, typically 12.6V max charge voltage.