There are a few things worth thinking about when shopping for a portable charger.
Ability: The capacity of a power bank is measured in milliampere-hours (mAh), but this can be a bit misleading because how much power you get depends on the cable you use, the device you are charging, and the charging method (Qi wireless charging is less efficient). You will never get the maximum capacity. We try to provide an estimate of what you’ll get in terms of device charges.
Speeds and charging standards: The charging rate for devices like smartphones is measured in watts (W), but most power banks list voltage (V) and amperage (A). Fortunately, you can calculate the power yourself simply by multiplying the voltage and the amperage. Unfortunately, getting that maximum rate also depends on your device, the standards it supports, and the charging cable you use. Many smartphones, including Apple iPhone, it supports Power Delivery (PD) standard, which means you can use higher wattage power banks to recharge your device without any hassle. Some phones, like Samsung’s Galaxy S range, support a complementary PD protocol called PPS (Programmable Power Standard) that goes up to 45W. Many phones also support Qualcomm’s proprietary Quick Charge (QC) standard. There are other proprietary fast-charging standards as well, but you usually won’t find power banks that support them unless they come from the smartphone manufacturer.
Pass through– If you want to charge your power bank and use it to charge another device simultaneously, you will need transfer support. Nimble, GoalZero, Elecjet, Biolite, Mophie, Zendure, and Shargeek portable chargers listed support for pass-through charging. Anker discontinued support for transfer because he discovered that differences between the output of the wall charger and the input of the device being charged can cause the power bank to turn on and off quickly and shorten its lifespan. We recommend caution when using the transfer as it can also cause portable chargers to get hot.
Travel: It’s safe to travel with a power bank, but there are two restrictions to keep in mind when boarding a flight: you must have the portable charger in your carry-on bag (it cannot be checked in), and it must not exceed 100 Wh (watt- hour). If your power bank has a capacity greater than 27,000 mAh, you should check with the airline. Below that shouldn’t be a problem.