Though you might not notice the difference when compared to any other QC 3.0 power bank, by reducing the number of chips PowerIQ 2.0 can make batteries smaller, lighter and more efficient. PowerIQ intelligently recognises the type of device to deliver an optimum charge, from 12W for the iPhone to 18W for the latest Android flagships. (Note that the PowerCore II will only be able to charge your device at 18W if that device supports fast charging.) The key difference between these two power banks, aside from the capacity and price, is the fact the larger model has two full-size USB outputs. However, only one of those outputs is an 18W PowerIQ 2.0 port; the second is a 12W PowerIQ 1.0 output. This is still ‘fast’ when compared to the 5W chargers bundled with iPhones and some other smartphones. More good news comes in the fact both power banks support fast charging on their Micro-USB input as well, so you can recharge the Slim in just four hours using a compatible charger. This goes a long way to make up for the fact it does not support passthrough charging, which is the ability to charge both the power bank itself and a connected device at once. Despite being from the same family of devices and building in the same technology, the two look nothing alike. Both are black rectangular devices with Anker’s branding on the top, but the 20,000mAh unit has a textured surface that improves grip in the hand. It’s also chunkier, and has eight LEDs built into its power button, while the Slim has four LEDs on the power bank’s top surface and a small power button embedded in its side. There’s a soft-touch silicone rear here too, which makes it feel better protected from drops. features a second Anker logo that takes up much of the surface. We like the auto-on support, meaning you don’t need to fiddle around with buttons – you just plug in your phone or tablet and charging begins. But beyond this the Anker power banks are really about pure speed over anything else. The slim, in particular, doesn’t strike us as significantly smaller than any other 10,000mAh power bank – when compared to the 10,000mAh PowerCore Speed it is indeed slimmer, but significantly taller, which makes it feel bigger. It has a nice design, but it’s still just a black plastic power bank, and it doesn’t feature the extra LEDs of the 20,000mAh model or a fancy LCD screen for an exact readout. There’s no support for USB-C or Lightning, and no extra features such as an LED flashlight. But you do get a mesh carry case, which is a nice touch and welcome for keeping the power bank and cables together. And, to be fair, what you do get is very reasonable for the money. In terms of capacity the PowerCore II 10,000 Slim is good for at least two charges for most Android phones and three charges for an iPhone. Double that for the 20,000mAh model. That you don’t get more charges is due to the fact some energy is lost through voltage conversion and heat generated – normal for a power bank. Marie is Editor in Chief of Tech Advisor and Macworld. A Journalism graduate from the London College of Printing, she’s worked in tech media for more than 17 years, managing our English language, French and Spanish consumer editorial teams and leading on content strategy through Foundry’s transition from print, to digital, to online - and beyond.