There are a few things worth keeping in mind when purchasing a portable charger.
Ability:The capacity of a power bank is measured in milliamp-hours (mAh), but this can be a little misleading because how much power you get depends on the cable you use, the device you’re charging, and the charging method (Qi wireless charging is less efficient). You’ll never get the maximum capacity. We’ve tried to give an estimate of what you’ll get in terms of device charges.
Charging speeds and standards:The charging speed of devices like smartphones is measured in watts (W), but most power banks list the voltage (V) and amperage (A). Luckily, you can calculate the wattage yourself by simply multiplying the voltage and amperage. Unfortunately, getting that top speed also depends on your device, the standards it supports, and the charging cable you use. Many smartphones, including Apple’s iPhones, support the Power Delivery standard, meaning you can use higher-wattage power banks to top up your device without issue. Some phones, like Samsung’s Galaxy S range, support a complementary PD protocol called PPS (Programmable Power Supply) that goes up to 45W. Many phones also support Qualcomm’s proprietary Quick Charge (QC) standard. There are other proprietary fast-charging standards out there, too, but you generally won’t find power banks that support them unless they come from the smartphone manufacturer.
Step through:If you want to charge your power bank and use it to charge another device simultaneously, you’ll need support for direct charging. The Nimble, GoalZero, Biolite, Mophie, Zendure, and Sharge portable chargers listed all support direct charging. Anker stopped supporting direct charging on some of its products because it found 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 rapidly and shorten its lifespan. Monoprice also does not support direct charging. We recommend that you be careful when using direct charging as it can also cause portable chargers to heat up.
Travel:It is safe to travel with a power bank, but there are two restrictions you need to keep in mind when boarding a flight: you must carry the portable charger in your carry-on luggage (it cannot be checked in) and it must not exceed 100 Wh (watt-hours). If your power bank has a capacity greater than 27,000 mAh, you should check with the airline. Below that, there should be no problem.
