The main function of a power bank is to charge your portable electronics, including smartphones, tablets, digital cameras etc. without connecting it to a power outlet such as AC socket. If you're like me, you probably found yourself at least once in a situation when you run out of battery juice in your smartphone and desperately look for a way to recharge it. A charged power bank can be very convenient in such times, it also gives you peace of mind. Even if you are not low on battery, you migh use your power bank to help someone else out.
Power banks are also called battery packs, external batteries, portable chargers, fuel banks, and they come in various shapes and sizes. There are small ones, which will recharge your smartphone once or twice, medium ones that can be used to recharge your tablet's battery or your smartphone many times, and the bigger units with multiple outlets that can also recharge your laptop on the go.
The battery is the most important element of the power bank, and its size is usually rated in miliamp-hours (mAh). The typical ranges available are between 2,000mAh available in pocket-size units up to 50,000mAh that can are more suited to carry in your bag or backpack.
Here is what charging performance you can expect from different battery sizes:
2,000mAh - recharge your smartphone in emergency (maximum once)
5,000mAh - charge a smartphone up to 3 times, and a tablet 1 - 1.5x
10,000mAh - multiple smartphone charges (4 - 8 times), tablet 2 - 3x
50,000mAh - mulitple smartphone/tablet charges, recharge your laptop
Most power banks come equipped with USB ports, which can be used to charge most portable devices today. It is important to understand that USB ports deliver different power output, most commonly 0.5Amp, 1Amp or 2.1Amp. The higher the Amp output in the USB port, the faster it can charge your smartphone (up to a limit).
When your power bank has more than one USB port, things get a bit more interesting. Depending whether you are charging only one device or two at the same time, the charging speed could be different. That is why you should be looking not only at how many Amps of output the single USB port has. You should also check how many Amps in total the power bank can deliver.
For example, if you have 2 USB ports in your power bank, one rated at 2.1Amp and the second at 1Amp, with total output 2.1Amp, you will be able to charge your smartphone at optimum speed only if there are no other devices being charged at the same time. If you connect another smartphone, both of them will be charged at around 1Amp, which will take longer.
Your power bank will usually include a charging cable, typically a USB or micro-USB cable, which you will connect to USB wall charger or another charging device, such as laptop. The accepted power input is also measured in Amps, and the higher the input Amps, the faster the power bank will recharge (this also depends on the power output supplied by your USB wall charger).
Below we listed some of the most popular power banks available today:
Solio Xcellerator is a solar panel + battery pack combo. The power bank can be used to charge most types of portable electronics, including smartphones, tablets, cameras etc. A fully charged 2,000mAh lithium-polymer battery can be used to charge a smartphone around 1 - 1.5 times. The unit has a special Apple output mode, which is optimized for Apple devices. The power bank itself can be recharged from either solar panel (4 to 6 hours in direct sunlight) or through any USB port (in around 4 hours).
Renogy Firefly provides up to 175Wh of energy and can charge USB as well as AC appliances on the go. (up to 150W) This solar suitcase includes two high-efficiency solar panels rated at 10W for a total output of 20W, 10Amp solar charge controller, 150 power inverter and one 16 Amp Hours lithium polymer battery. The case is made from a durable and waterproof material, made to work in all-weather conditions. It has been designed for off-grid use and emergencies.
MaxOak 50,000 mAh can charge all your smartphones, USB devices and even most laptops (except Apple). At 8.1 x 5.3 x 1.3 and just under 3 pounds it is one of the smallest laptop power banks on the market. The charger has 6 output ports: 20V/3A for laptops, 12V/2.5A for digital cameras, two 5V/2.1A USB ports and two 5V/1A USB ports for smartphones, tablets and other portable electronics. The power bank can be recharged in 6-8 hours using AC or DC power, and when fully loaded it can be used to charge your iPhone 6 around 17 times. MaxOak is compatible with most laptops and comes with 11 different connectors to suit your notebook. (check if there is a connector for your laptop before buying)
mophie Powerstation XL has the capacity of 12,000mAh, which means you can charge your smartphone phone up to 4 - 8 times (depending on the model). Your iPad should be recharged 1.5 - 2 times. It has two charging USB ports, and can charge at 500mAh, 1A and 2.1A. It is only 2.8 x 0.9 x 4.5 inches, and weighs just under 16 oz.
Poweradd Pilot 2GS has a 10,000mAh lithium-polymer battery, which is capable of charging your iPhone 6 four times, and your Galaxy S6 up to 2.5 - 3 times. Dual USB ports are rated at 2.1A + 1Ah, and can adjust the adequate charge automatically. It has been designed to be portable and durable. Poweradd offers a 24-month limited warranty on this model.