Lightning was introduced by Apple in September 2012 with the iPhone 5, fifth-generation iPod touch and seventh-generation iPod nano. A month later the technology was added to the fourth-generation iPad and original iPad mini. Older iOS devices use the 30-pin dock, but if you have any of these or later iOS devices then the Aukey 3600mAh External Battery Charger is well worth a look. Particularly the iPhone. Aukey doesn’t state its battery’s efficiency, but with most offering around 70 percent (some is lost through heat generated and voltage conversion), you can expect around 2500mAh. That’s not enough to completely fill an iPad’s battery, but it would fill an iPhone 5 (1440mAh), iPhone 5c (1507mAh) or iPhone 5s (1570mAh) around 1.7 times, an iPhone 6 (1810mAh) around 1.5 times, and it would give an iPhone 6 Plus (2915mAh) just under a full charge.   The LED will go through various colours while charging to show you how much power remains: white means more than 60 percent; green is between 20- and 60 percent; and red is below 20 percent.  Also see: Best MiFi 2016. The battery tech inside this power bank supports auto-on/-off, too, so you can plug it in and leave it be: it’ll automatically switch off when either it or your iPhone’s battery is full, with no unnecessary wastage.  Note that this Aukey power bank will charge your iPhone faster than it will fill its own battery. That’s because it has a 7.5W input and just a 5W input. Apple’s own iPhone charger is rated at just 5W, but if fast charging is what you need then you should note that some power banks offer up to 12W via USB. (Charging your iPhone at more than 5W will not hurt its battery.) Also see:  how to charge your smartphone or tablet faster.   Leaving the tech aside, the Aukey 3600mAh External Battery Charger is a nice-looking device. It’s built from matt black plastic, with rounded edges and a very slim (12mm) and light (85g) design. There’s just a single output, but at this capacity a second output would be pointless.  Aukey supplies a soft carry case if you’re throwing the External Battery Charger into a bag, but you’d hardly notice this thing in your pocket. Intriguingly it also supplies a lime green suction pad, and we have no idea why. Read next:  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.