Anker's compact power bank can charge your iPhone up to 7 times, or two devices simultaneously.

The Anker PowerCore 20100, an external battery charger for the iPhone 6s or earlier, is the latest upgrade from the 16000 predecessor, featuring fast charging technology on both of its USB outputs. That means both ports have an output of 2.4A, providing a total of 4.8A overall. Included with the power bank is a 23.5-inch microUSB cable that can be used to recharge the PowerCore at 2A with an appropriate wall adapter that will support the speed.

Its 20,100mAh capacity gives it some weight — 12.6oz to be exact — but that's a lot of backup battery life whether you're using 1 device or 2. Anker has included a nice mesh carry bag for the PowerCore, too. The compact size of the power bank (6.5 x 2.3 x 0.9-inches) makes it easy to even slide in your pocket if needed.

The plastic shell of the PowerCore sports a nice matte finish that's easy to grip, but still manages to show some fingerprints when in the right lighting. The front features 4 blue LED lights that signify how much juice is left in the power bank — 1 light = 25%, 2 lights = 50%, and so on.

You can tap the power button the side at any time to check the battery level, but when it's fully charged the lights will completely shut off.

When you plug your iPhone into the PowerCore 20100 they'll instantly start to charge, which isn't the case on many aftermarket power banks (some require you to power it on first).

There are safety features built in as well, such as surge and short circuit protection. Anker's PowerIQ and VoltageBoost technology allow the PowerCore to automatically provide the fastest possible charge to your iPhone or iPad that's plugged in — up to 2.4A, of course.

For the impressive battery life that this compact power bank packs you really can't go wrong. It doesn't look or feel cheap, and its design is simple and straightforward.

Whether you're going off the grid for a weekend or just need an emergency charger on hand when your devices hit critical levels, this will boost your battery quickly and efficiently. You can get the Anker PowerCore 20,100 in black or white for $39.99 straight from Amazon, including a nice 18-month warranty.

$39.99 from Amazon