You might be wondering why, if an iPhone 5s battery is rated at 1570mAh, and this EC Technology power bank offers 22400mAh, you can charge your iPhone 5s ‘only’ 10 times. As with all portable USB chargers, some of the power is lost through the transfer of energy and in the heat generated. Most chargers will lose around 35 percent of their capacity; this EC Technology High Capacity Power Bank is more efficient and will lose only 30 percent. We’ll do the maths for you: that leaves 15680mAh for charging your assorted USB-powered gadgets. Given that this power bank has dual-USB outputs – one rated at 2.1A and designed for but not exclusive to tablets, the other at 1A for smartphones – it’s nice to see that EC Technology bundles two USB cables in the box. These come with interchangeable connectors for Apple’s 30-pin dock, Micro- and Mini-USB, plus what looks like an old Nokia charger. If your device uses a proprietary connector – such as Apple’s Lightning – you can still charge it, you’ll just need to supply your own cable. Also see: 41 best smartphones. With such a large amount of portable power on offer, it’s also pleasing to see the Micro-USB input rated at 2A. You can use any USB charger to top up the EC Technology Power Bank (one is not supplied), although charging will be faster using those with higher ratings, such as those sold with tablets. Using a 2A charger the power bank can be charged up in 14- to 15 hours, but it’ll take 27- to 29 hours using a 1A USB charger. Our previous experience in charging up the Veho Pebble Smartstick+, which has a 0.5A input, means we know which option we prefer. Despite all that talk of energy loss through the heat generated, in simultaneously charging our iPad mini 2 and Samsung Galaxy S4 the EC Technology High Capacity Power Bank never got even warm to the touch. It’s actually not a huge amount larger than the S4 either, although it’s significantly heavier: at 449g this is a gadget you carry in your bag, not in your pocket. Like that device it uses four LEDs to show you how much capacity remains. Given that each LED refers to a huge 5600mAh, you can’t get an exact reading. Unlike the Lumsing, though, it also features a torch (double-press the tiny button on the side to turn it on). You never know, if you’re taking the EC Technology High Capacity Power Bank on a camping trip it could come in useful for late-night trips to the shower block, or even just trying to find the MicroUSB connection on a flat phone or tablet. Also read our tips on how to improve smartphone battery life. 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.