Also see: Best Black Friday Gadget Deals At first glance the TP-Link appears to be a cheap and cheerful, but rather basic power bank. A white plastic cylindrical device with an intriguing diamond-patterned grippy service, it isn’t especially feature rich, yet gets the job done as intended. Actually there’s more to it than meets the eye. No power bank is able to deliver its full advertised capacity for charging your USB devices. Energy is lost through the heat that is generated in charging, and in voltage conversion. The industry standard is around 65- to 70 percent efficiency, which means that bulky 20,000mAh power bank that feels like a brick in your handbag will actually provide you with only 13,000mAh. Also see: How to charge your phone’s battery faster. While that wouldn’t fully charge our Samsung Galaxy S6 (which has a 2,550mAh battery) when new, the chances are the battery isn’t going to be entirely depleted when we plug in a portable power bank – and in any case, it’s very nearly a full charge. Some Android phones come with higher-capacity batteries still, and the only way to be sure is to check your own phone’s spec. If you have an iPhone, you’ll get more like 1.5 charges out of this TP-Link TP-PB2600. Also see: Best desktop chargers 2016. The TP-Link’s high 90 percent efficiency rate is matched by the slightly higher-capacity Anker Astro Mini 3350mAh power bank. The two devices are very much on par with each other: the Anker has a more attractive metal design and a higher capacity, but the TP-Link is £5 cheaper and works faster to refill its own battery. (Note that the Anker’s capacity has been upgraded since the time of our review.) The TP-Link will work with any sort of phone or tablet – a Micro-USB cable is supplied in the box and, if yours uses a different type of cable such as Lightning, you can add your own proprietary cables. That said, even with its high efficiency rate its 2,600mAh capacity won’t get you far with a tablet battery. Also see: Best MiFi 2016. The TP-Link has one USB output and one Micro-USB input at one end. These are both rated at 5W, which is slow compared with high-capacity power banks but about standard for a small lipstick-style portable charger such as this. Of course, it doesn’t necessarily matter how long it takes to charge your phone since both will likely be in the same pocket or bag. Also see: How to improve smartphone battery life. Although you can plug in both cables at the same time, the TP-Link TP-PB2600 won’t charge up a phone while it’s busy refilling its own battery (this is known as passthrough charging). We’d prefer to see this functionality supported, but given the relatively small capacity it’s not a huge issue. There’s just one LED on the TP-Link power bank, which will blink when charging itself or when charging another device and its battery is low. If there’s plenty of battery (TP-Link doesn’t specify the exact amount) the LED is constant. A small button below the LED is used to check the battery level; on our Galaxy S6 the TP-PB2600 automatically began charging when we inserted the cable. The TP-PB2600 is one of three power banks in TP-Link’s line-up. We’ve already reviewed the £21.83 TP-Link TL-PB10400, which is a dual-output device with a 10,400mAh capacity that is more convenient if you have more than one device to charge or need to do so faster or over several days. There’s also the £16.99 TP-Link TL-PB5200, which sits in the middle of the two as a single-output but higher-capacity bank with 5,200mAh to hand. Read next: What is Qualcomm Quick Charge 3.0? Plus: the best QC 3.0 devices and accessories. 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.