With 12,000mAh of power inside this bank its size comes as no surprise, but its 158mm width is awkward for slipping into a pocket. This is a power bank you will carry in your bag, where you may notice its 248g weight. Four LEDs sit on the top surface of the device, and allow you to see at a glance exactly how much power remains before the device needs refilling. We would prefer to see an LCD with an exact readout, but at this price its omission is understandable. Also see: How to charge your phone’s battery faster. Tronsmart says the Presto uses high-performance ATL battery chips, but its claims of being able to recharge an iPhone 6 4.5 times or a Samsung Galaxy S7 edge 2.5 times would suggest it has an efficiency rating of around 70 percent. (Somewhere between 60- and 70 percent is the industry standard, though some power banks such as the Zendure A2 can offer higher efficiency.) As a guide, you can expect around 9,000mAh of usable power from the Tronsmart Presto. See all power bank reviews Arguably just as important as how much power it can offer is how quickly it can deliver that power, and this is where the Tronsmart Presto shines. At first glance it has a single full-size USB output that supports the fastest Quick Charge 3.0 protocol, which can recharge a compatible device up to four times faster than a conventional charger. Look again, though, because the input also acts as a second output. This is a USB-C port, which is beginning to become more common among new flagship Androids, and is much faster than Micro-USB with a 5V, 3A rating. Refilling the Tronsmart Presto via USB-C rather than Micro-USB is therefore possible in just 6.5 hours – it’s only a shame that the power bank doesn’t allow you to use it while doing so, a process known as passthrough charging. Also see: Best MiFi 2016. While the USB-C input/output is futureproof, fast and conveniently reversible, this blessing is also a curse. Tronsmart supplies a single USB-C to USB-A cable in the box, which is fine for refilling the Tronsmart Presto, and for charging a USB-C phone from the full-size Quick Charge 3.0 port. If you have an Android phone that uses the much more common Micro-USB port, or you have two devices that charge over USB-C, you’ll need to supply your own USB-A to Micro-USB and USB-C to USB-C cables. A problem with all USB-C devices right now is that you likely have only one compatible cable – that which came with your new phone – and you might prefer to leave it at home where it’s safe. Then again, USB-C is the future for Android phones, and will become more common over time. Also see: How to improve smartphone battery life. Another small gripe with the Tronsmart Presto is that it doesn’t support auto-on, which means you need to attach your phone and then press the small button on its side to begin charging. This is less convenient, but clearly not the end of the world. Read next: Best desktop chargers 2016. 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.
