Portable chargers are great for keeping your smartphone, tablet and other USB-connected devices going for as long as you do, and this 18000mAh External Battery Pack from EC Technology is more stylish than most in its 12mm ultra-slim matte-aluminium chassis. Also see:  Best power banks 2018.  It’s also a lot heavier than most at 540g, and portable only in the sense that you might throw it in a travel bag. Pocket this 18000mAh External Battery Pack and it will pull down your trousers. If you’re looking for something that balances portability and power, check out the Lumsing 10400mAh Power Bank.  Our review sample is a sleek black slab, and the External Battery Pack also comes in stylish pink, silver and green. On top is EC Technology’s logo, and below you’ll find legends for each of the ports – all lie on the device’s right side. Also here is a four-LED status light that doubles as a torch, although at 122mm wide this External Battery Pack is the oddest-shaped torch we’ve ever held.  As we’ve mentioned in previous portable USB charger reviews, the problem with using an LED system to denote the remaining capacity is that each light represents a huge amount of battery capacity – 4500mAh in the case of the EC Technology 1800mAh External Battery Pack.  It’s important to note that although this charger offers a huge amount of juice for your USB devices, only around 70 percent of its quoted capacity will make it to your gadgets, with energy lost through heat generated and voltage conversion. This compares well with other power banks, which typically have a 65 percent efficiency rate.  With both 1A and 2.1A outputs available, the EC Technology 1800mAh External Battery Pack offers fast charging for your devices. You can plug a smartphone or tablet into either port (they will draw only the power they need), but for charging a tablet you’re better off using the 2.1A output – especially if it’s an iPad, which are known to be fussy about from where they fill up.  Slightly concerning is the 1.2A Micro-USB input. You can charge up the External Battery Pack using the charger that came with your phone or tablet, but at 1.2A it will fill up slower than its 22400mAh brother.   Given that there are two USB outputs, it’s pleasing to see that EC Technology has bundled two USB cables in the box. These come with interchangeable heads for Micro- and Mini-USB, Apple’s 30-pin dock and what looks like an old Nokia charger. If your device uses a proprietary connection – such as Apple’s Lightning – you’ll simply need to plug in your own cable. 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.