I’m a big fan of power banks. They are handy if I’m on a road trip, shooting a long time lapse on my phone, or just away from an outlet for some reason. They come in all shapes and sizes, from thin ones like the 1byone 10000 power bank to really small ones like the Anker PowerCore Mini: there’s one for every use case. Today, we’re taking a look at the Anker PowerCore 20100, one of the biggest in Anker’s fleet of PowerCores. First off, let’s look at the hardware. This 20,100 mAh power pack is 6.5 inches long and has a hefty weight (12.5 oz) to it—definitely something you’ll want to keep in your backpack. On one end, you’ll find two USB ports, and a microUSB port for charging the power pack. There’s a button on the side for checking the current power level, but sadly, there’s just four LEDs to indicate the battery level in increments; 25%, 50%, 75%, and 100%. While there’s really nothing wrong with this method, I much prefer the LCD display on the 1byone 10000 power bank. I’ve been throwing around the term “mAh” quite a bit, and I’ve mentioned that this product is 20,100 mAh. But what does that even mean? According to GSMArena.com, “The milliampere-hour (mAh) is one-thousandth of an ampere-hour and is a technical term for how much electrical charge a particular battery will hold.” The more mAh a battery has, the longer that battery will be able to run. Of course, when it comes to phones, a 6-inch phone will not go as far on a 3,000 mAh battery as a 4.5-inch phone would be able to. But, when it comes to power banks, it is much simpler: the more mAh, the more devices it can power on a single charge. Armed with this knowledge, one would think that the Nexus 6P—with a 3,450 mAh battery—could be charged 5.8 times off of this PowerCore. However, a perfect charge is not possible because of battery capacity loss (energy loss caused by external factors). Some basic calculations suggest that this power bank has a 63% efficiency, so the reality is that you would be able to charge a Nexus 6P about 3.6 times. Here’s how that lines up with other devices: iPhone 7: 6.4 times iPhone 7 Plus: 4.3 times iPhone 6S: 7.3 times iPhone 6S Plus: 4.3 times Galaxy S7: 4.2 times Galaxy S7 Edge: 3.5 times Nexus 5X: 4.7 times Nexus 6P: 3.6 times Pixel: 4.5 times Pixel XL: 3.6 times Calculation for anyone curious: 20100/phone battery mAh * .63. Now, how about the charge times compared to a wall charger? The charge times on the PowerCore 20100 will be the same as with a wall charger. This is thanks to the Power IQ built into this power pack. You don’t even have to worry about plugging your device into the USB port with the correct voltage—Power IQ handles that too. Sadly, there’s no USB-C on this PowerCore, so many recent phones equipped with USB-C will have to charge at the slower rate using a USB-A to USB-C cable. While the PowerCore 20100 is able to charge your devices as fast as a wall charger, be prepared for this power pack to take around 10 hours to charge itself (or up to 20 hours, if you have a 1 amp charger instead of a 2.4 amp charger). When you take a step back and look at this power bank, it looks simple—and it is—but there is quite a bit of engineering inside this product that makes it work extremely well. If you need a high capacity power bank, then I highly recommend the Anker PowerCore 20100. This is perfect for long road trips, flights, or just having around as a backup should you lose power.