How to Choose a Power Bank: Capacity, Charging Speed and Safety

A power bank is one of the most useful accessories you can carry, but the specifications on the box are not always easy to read. This guide explains what actually matters when you are choosing one.

Understanding capacity: mAh and real-world output

Capacity is usually printed in milliampere-hours (mAh). A common point of confusion is that a 10,000 mAh power bank will not deliver a full 10,000 mAh to your phone. Energy is lost during voltage conversion, so the usable output is typically around 60-70% of the printed figure. As a rough guide, a 10,000 mAh power bank will fully charge most smartphones once or twice, while a 20,000 mAh model is better suited to multi-day trips or charging several devices.

Charging speed: watts matter more than ports

Charging speed is determined by wattage (W), which is voltage multiplied by current. A charger rated at 5V/2A delivers 10W, while a fast-charging model may deliver 18W, 30W or more. To actually get fast charging, three things must all support it: the power bank, the cable, and your device. If any one of them is limited, the whole chain runs at the slower speed. This is a common reason people find their "fast" charger is not fast.

Ports and protocols

Modern power banks generally use USB-C for both input and output, often alongside one or two USB-A ports. USB Power Delivery (USB PD) and Quick Charge (QC) are the two most widely supported fast-charging protocols. Checking that your phone and power bank share a protocol is more useful than simply comparing the number of ports.

Air travel rules

Power banks must be carried in hand luggage, never in checked baggage. Airlines assess them by watt-hours (Wh) rather than mAh. To convert, multiply the mAh figure by the cell voltage (usually 3.7V) and divide by 1,000. A 20,000 mAh power bank therefore works out at roughly 74Wh. Under widely applied international rules, units up to 100Wh are generally allowed without special approval, 100-160Wh require airline permission, and anything above 160Wh is not permitted. Rules can differ by carrier and country, so it is worth checking with your airline before travelling.

Safety features worth looking for

Quality power banks include protection circuits for over-charging, over-discharging, short circuits and over-heating. A power bank that becomes uncomfortably hot in normal use, swells, or refuses to hold charge should be taken out of service. Buying from a brand that offers a warranty and after-sales support matters more here than saving a small amount on the purchase price.

A practical checklist

Match the capacity to how you actually travel; confirm that the wattage and protocol suit your phone; use a cable rated for the speed you want; and choose a product with genuine protection circuitry and warranty cover.

AMAYA offers a range of power banks, along with chargers and data cables to match. All AMAYA products pass factory quality testing and are covered by an official warranty.