This guide covers the essentials of power banks and portable charging in one place — the standards, trade-offs, and practical buying advice that matter most.
- Capacity (mAh or Wh) and output wattage are separate specs — a power bank can have huge capacity and still charge slowly if its output port is limited.
- Realistic device-charge counts are usually lower than marketing numbers suggest, once conversion losses are factored in.
- Airline watt-hour limits are the most commonly overlooked constraint when buying a power bank for travel.
The rest of this section breaks each of these topics down in more depth, covering specific devices, standards, and buying scenarios.