Built into a silver aluminium shell with blue trim and black polished plastic ends the Lumsing Grand A1 is a good-looking power bank that feels as though it should be resistant to wear and tear – a good thing, since no carry case is supplied. For a power bank of this capacity it’s not overly large or heavy, weighing in at 262g and measuring 98x79x21mm. A Lumsing logo is printed on the front of the Grand A1 with the slogan ‘Connecting simple life’. As is standard for power banks you’ll find some key specs printed on the bottom, plus legends for the twin outputs and input (which we’re not entirely sure are necessary) on top. There are four tiny holes in the front of the device, through which blue LEDs shine to reveal how much power is remaining. Each represents 25 percent or 3,350mAh, which with a claimed 90 percent efficiency rating is the equivalent to one full charge for a standard Android phone. Also see: How to improve smartphone battery life. The LEDs are activated with a tap of the side-mounted blue button; a long-press activates the small LED flashlight on the Grand A1’s top. It’s not the brightest or largest of LEDs, but it could prove handy as you fumble around for charging cables in the dead of night. The Lumsing Grand A1 is supplied with a single Micro-USB cable (if your phone or tablet uses a different connection you must provide your own USB cable), although there are two full-size USB outputs. Lumsing doesn’t specify the exact specification of each, but between the two there is a maximum total output of 15W. The Lumsing uses intelligent charging to recognise your device type and automatically deliver the optimum amount of power (provided that is available), which means if you have two power-hungry devices attached each will net 7.5W. That’s faster than many USB chargers bundled with smartphones, but there are other power banks that can deliver up to 12.5W of power on each port – plus those that support the even faster Qualcomm Quick Charge standard. Also see: Best desktop chargers 2015. Nevertheless, the Lumsing will prove a handy gadget to have about you should your phone and/or tablet run down. How many charges it will offer to your phone or tablet depends on the capacity of their own batteries, but with 13,400mAh available (of which you should see as much as 12,000mAh) you can expect in excess of four full charges for a decent Android phone and between seven and eight for an iPhone. When the Lumsing itself runs out of power you can hook it up to the USB charger that came with your phone or tablet and, depending on the specification of the charger (the Grand A1 can accept up to 9W input) you could see it go from zero capacity to full in eight hours. That’s more or less an overnight charge, so it’s a pity you won’t be able to plug in your phone or tablet at the same time (passthrough charging) – you’ll need a second USB wall charger to simultaneously charge both devices. Also see: Best MiFi 2016. Read next: How to charge your phone or tablet faster. Follow Marie Brewis on Twitter. 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.