Start by deciding which devices you want to charge and how often you will be away from a wall outlet. A power bank's capacity is usually stated in milliamp-hours, but that number does not translate directly into the same amount of usable energy at a device. Conversion losses, cable quality, charging speed, and the device's own battery all affect real-world results.
Check the output ports and supported charging standards. A bank that can charge a phone may not provide enough power for a laptop, even if both use USB-C. If you plan to charge more than one device, confirm whether the available output is shared across ports. Consider size and weight as well: a larger capacity can be useful for travel, but it may be inconvenient to carry every day.
Choose a product from a reputable maker and follow its instructions for charging, storage, and use. Inspect cables and connectors for damage, and stop using a battery that is swollen, unusually hot, or visibly damaged. Keep the bank in a dry, protected place and check applicable travel guidance before flying. Recharge it periodically if it sits unused, and use a suitable charger rather than a questionable high-output accessory.
Making Sense of Capacity, Wattage and Everyday Use
Once you know which devices you want to charge, it helps to translate the numbers on the box into something practical. Most power bank cells run at a nominal 3.6 or 3.7 volts, while USB output is delivered at 5 volts or higher. Because of that voltage difference, plus heat and circuitry losses, a rough working assumption is that you will get somewhere around 60 to 70 percent of the rated milliamp-hour figure into your devices. A more useful comparison is watt-hours (Wh), which many makers print on the label. Compare that with your phone or tablet battery, which is often listed in the device specifications, to estimate how many full charges you can realistically expect.
Matching output to the device
Charging speed depends on both ends agreeing on a standard. USB Power Delivery (USB PD) is common for phones, tablets and many laptops, while some phones also support proprietary or Qualcomm Quick Charge modes. Look for the maximum wattage per port rather than just the combined total. As a general guide:
- Phones and earbuds: 18 to 30 W from a single USB-C port is usually plenty.
- Tablets and handheld consoles: around 30 to 45 W keeps charging reasonably quick.
- Laptops: check the wattage of the original charger; a bank offering 60 W or more on one port is often needed, and it should match or come close to that figure.
Remember that a USB-C cable also needs to be rated for the current involved. A basic cable may limit a laptop to slow charging even if the bank is capable of more.
Features worth checking
Pass-through charging lets you charge the bank and a connected device at the same time, which is handy overnight in a hotel. A small display showing remaining percentage is more informative than four indicator lights. Some banks also recharge themselves quickly over USB PD, which matters if you only have a short stop between journeys. A low-current mode can be useful for small wearables that otherwise fail to trigger charging.
For flying, airline rules commonly treat banks under 100 Wh as permitted in cabin baggage only, with larger sizes needing approval, but always confirm with your carrier. If you are building out a travel kit, our guide to choosing a Wi-Fi router and other setup articles cover related gear for home and away.