Ultra-slim and clad with stylish gunmetal grey alumiunium alloy (also available in silver or black), the iHarbort power bank is perfectly proportioned for the pocket. It’s very well designed with its sleek, rounded edges, and sufficient attention to detail has been paid that the power button lies flush with the casing. The iHarbort power bank carefully balances capacity with size and weight, and with 5000mAh on offer you should get between one- and two full charges for your phone, depending on the model. With most power banks averaging around 70 percent efficiency, expect around 3500mAh to be available to your devices. Our Samsung Galaxy S6 (2550mAh) would receive just under one and a half charges, but an iPhone 5s (1560mAh) could potentially manage two and a quarter. Also see: How to improve smartphone battery life. Despite its budget price tag, iHarbort hasn’t skimped on features. We found this little power bank would automatically begin charging our phone when we plugged it in via USB and, when it was full, it would also shut off the power without our instruction. More importantly, we could simultaneously charge both the phone and power bank (also known as passthrough charging). Given that you’ll probably charge only one device with this power bank, it makes sense that there is just the one USB output. iHarbort supplies a micro-USB cable in the box; if you want to attach an iPhone or other smartphone with a proprietary cable you simply provide your own lead. Also see: Best MiFi 2016. Thankfully, this is a fast-charging port, rated at 10.5W (5V, 2.1A). That means this power bank will be just as happy to charge a tablet or other USB-powered device, although its capacity is better suited to a smartphone battery. The iHarbort also supports smart current control, which is able to detect your device type and battery capacity and deliver the optimum amount of power. Also see: How to charge your phone or tablet faster. And while the power bank is fast to give away its charge, it’s also quick to claw it back. The Micro-USB input on this iHarbort is rated at 10W (5V, 2A), so for the fastest charging you’ll want to refill it using a 10W mains adaptor (although you can use any USB charger, such as that supplied with your phone or tablet). You don’t get an LCD screen, although one really isn’t required at this capacity level, so you must judge how much power remains using the four LEDs on the power bank’s bottom edge. We particularly like the fact these lights switch off during charging, so when the iHarbort is used at night you won’t be disturbed by blinking LEDs. There are a couple of cost-cutting measures but, thankfully, their omission didn’t bother us in the slightest. Unlike many portable power banks the iHarbort is not supplied with a carry case (we don’t think you’ll need one in any case, and the iHarbort has a reassuring 18-month warranty), nor a built-in LED torch. Also see: Best desktop chargers 2015. 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.