GoKawiilThere are a few things worth thinking about when you’re shopping for a portable charger.
The capacity of a power bank is measured in milliampere-hours (mAh), but this can be a little misleading because the amount of power you get out depends on the cable you use, the device you're charging, and the charging method (Qi wireless charging is less efficient). You will never get the maximum capacity from any power bank. You can generally expect to get between 60 and 80 percent after energy loss through heat and conversion. Some manufacturers list a “Rated Capacity” that's lower than the overall capacity to give you an indication of what to expect in real world use. We try to provide a minimum estimate of what you’ll get in terms of charges for devices.
The charging rate for devices like smartphones is measured in watts (W), but most power banks list the voltage (V) and the amperage (A). Thankfully, you can calculate the wattage yourself simply by multiplying the voltage and 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’s iPhones, support the power delivery standard, meaning you can use higher-power power banks to recharge the device with no issues. A few phones, such as Samsung’s Galaxy S range, support a supplementary PD protocol called PPS (Programmable Power Supply) that goes up to 45 watts. Many phones also support Qualcomm’s proprietary Quick Charge (QC) standard. There are also other proprietary fast-charging standards, but you won’t generally find power banks that support them unless they come from the smartphone manufacturer.
Your device will need pass-through support if you want to charge your power bank and use it to charge another device simultaneously. The Nimble, GoalZero, Biolite, Mophie, Zendure, and Sharge portable chargers listed support pass-through charging. Anker discontinued support for pass-through in 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 cycle on and off rapidly and shorten its life. Monoprice does not support pass-through charging either. We would advise caution when using pass-through, as it can also cause portable chargers to heat up.