There are a few things to consider when buying a portable charger.
capacity: Power bank capacity is measured in milliamp hours (mAh), but this can be a bit misleading, as the amount of power you draw varies depending on the cable you use, the device you’re charging, and how you charge it (Qi wireless charging is less efficient). You won’t get the maximum capacity – we just try to give you a rough estimate of the capacity you’ll get in terms of charging your device.
Charging speed and standards: The charging speed of devices such as smartphones is measured in watts (W), but most power banks also list the voltage (V) and amperage (A). Thankfully, you can calculate the wattage yourself by simply multiplying the voltage and amperage. Unfortunately, whether you can achieve the maximum speed also depends on your device, the standards it supports, and the charging cable you use. Many smartphones, including Apple’s iPhone, support the Power Delivery standard, so you can use a higher-powered power bank to charge your device without any problems. Some smartphones, such as Samsung’s Galaxy S series, support a supplemental PD protocol called PPS (Programmable Power Supply) up to 45 W. Many smartphones also support Qualcomm’s proprietary Quick Charge (QC) standard. There are other proprietary fast charging standards, but you usually won’t find a power bank that supports them unless it’s made by a smartphone manufacturer.
Pass-through: If you want to charge your power bank and charge another device at the same time, you need pass-through support. The listed Nimble, GoalZero, Biolite, Mophie, Zendure, and Sharge portable chargers support pass-through charging. Anker dropped pass-through support for some of their products after finding that the difference between the output of the wall charger and the input of the device charging could cause the power bank to cycle on and off rapidly, shortening its lifespan. Monoprice also does not support pass-through charging. It is recommended to use caution when using pass-through as it can cause the portable charger to heat up.
trip: Traveling with a power bank is safe, but there are two restrictions to be aware of when flying: Portable chargers must be in carry-on baggage (not checked) and must not exceed 100Wh (watt-hours). If your power bank’s capacity is more than 27,000mAh, check with your airline; if it’s less than that, you’re fine.
