powerbank

Power bank, short for portable battery pack, is a compact rechargeable energy storage device used to charge mobile and other battery-powered devices when an outlet is unavailable. Most models contain a lithium-based cell, a battery management system, and protective circuitry inside a small enclosure with one or more input and output ports. Capacity is typically rated in milliampere-hours (mAh) or watt-hours (Wh); common consumer packs range from about 5,000 to 20,000 mAh (roughly 18 to 74 Wh). Larger units exist for tablets or laptops. The stated capacity is usually the nominal cell capacity; actual usable energy is reduced by conversion losses and protection circuitry.

Operation involves charging the pack from a wall charger, USB charger, or wireless charger, then drawing power from an output port to charge a connected device. Output interfaces include USB-A and USB-C, with many models supporting fast charging standards such as USB Power Delivery or Quick Charge; some packs also include wireless Qi charging. Safety features typically protect against overcharge, overdischarge, short circuit, and overheating.

Life and use: batteries age with cycles, and capacity declines over time. Proper use includes avoiding extreme temperatures, using certified cables, and not attempting to open or modify the pack. Power banks add portability for smartphones, wearables, cameras, and other devices, but higher-capacity models are heavier and less convenient for everyday carry.

Regulatory note: in air travel, spare power banks are usually limited to 100 Wh per battery (approximately 27,000 mAh at 3.7 V) and must be carried in cabin baggage; higher-capacity units generally require airline approval or are prohibited. Regulations vary by country and carrier.